The SDR Approach to Ham Radio..
This is a "living spreadsheet" (meaning it will be updated periodically) of the parts, part numbers, supplier and approximate cost. Includes a listing of Suppliers.
NOTE : I have set up the website www.n6qwradiogenius.us as a further repository of information pertaining to this project. Yes I do have the audacity to call myself a radio genius but that is certainly well founded, unlike some who call themselves a stable genius.
A new beginning for all of us. Are you willing to take the plunge????
June 27th, 2019 ~ Gee, I haven't blogged in 3 days and nobody checked to see if I was Dead? Guess I know where I stand!
Well there is a reason I was not blogging and it was that I was chasing a problem with the transmitter side. I believe we may be close to a resolution; but I wanted to share some of my adventures in finding the problem.
On the 24th I got a very nice email from a ham who said that I was transmitting double sideband and that she could see my carrier on a webSDR receiver. Now that is not good news. So I started to look for some possible areas where the problem could be centered. Receive worked OK; but it was something on transmit.
I am sure there will be those who are thinking --should have used the Tayloe Detector circuit and not the ADE'1's. I will bite my tongue and stop there.
But let us do some analysis at the circuit block level and see if we can focus on what may be happening. Firstly the ADE-1's are acting much as they do in conventional hardware based transceivers all of us have built. On receive the ADE-1's are product detectors and on transmit they are balanced modulators.
Or for those who want to be precise for this project -- on receive they are direct conversion receivers and on transmit they are direct conversion transmitters. But they are different in the sense that one of the signal channels is in phase (I) and the other is out of phase by 90 degrees or quadrature (Q). Mathematically these signals on transmit are combined in our hybrid transformer and band pass filter to result in a single signal output at the operating frequency. That output can be of various modes. It is all mathematics --- you know those sines and cosines that add, cancel and subtract. If you look at the schematic of Softrock V6.3 transceivers you will see the two outputs from the Tayloe Detector are combined in a similar hybrid transformer located on the PA Filter board.
So now our analysis must look at -- it receives OK but the problem is transmit. We indeed are creating I and Q channels starting with the hybrid combiner transformers and those split signals are mixed in the ADE-1' with the quadrature signals from the 74AC74. We must conclude that since receive is OK then indeed the LO is providing the two quadrature signals, the hybrid transformer is working and so are the ADE-1's. The line input to the sound card is working as well. Since there are many common elements for receive and transmit, what is different?
The one and only difference is the Line Output from the Sound Card to the DPDT relay that in's/out's to the ADE-1's. So that ought to be easy to check. I got my scope out and put it on the common leaf's that goes to the ADE-1's. This was done to isolate the signal, as another possibility was a bad NO contact on one of the channels. Hey cheap relays from China --they were liable to be seconds. Well in transmit one leaf has audio and the other didn't!
Ah Ha -- bad relay or bad sound card output. So to eliminate the sound card I pulled the 3.5 MM stereo Line Out plug and put my scope on both channels and put the Quisk in the SPOT Mode. Boom, we had output on both channels of the plug. So the next test was to measure at the NO contact pin (not the leaf). No signal on one of the channels! So it wasn't the relay.
But it was the stereo jack which wasn't stereo but monaural with a shorting switch. About a month ago I was out of stereo connectors so I ordered 10 (price break). When I was installing the "stereo" jacks I reached in the bin a pulled out two -- one was stereo which went into the Line In side but the monaural was installed in the Line Out. Well that sure drove me nuts. I then went to the bin -- there are eight stereo jacks remaining --wrong only seven as one of those remaining is also monaural.
So that was one piece of the puzzle. I also thought more about the hybrid combiner transformer and changed that over to a trifilar wound with equal numbers of turns. One winding connects to the output of the Band Pass Filter. the other two windings are connected much like a bifilar transformer with the common connection to ground and the other ends connected to each ADE-1. I also upgraded the Band Pass Filter to the same design used by N2CQR in his DigiTia. So that is three hardware changes.
There are no silver bullets in homebrew construction! So I next thought about the possibility of over driving the ADE-1's These DBM like to see no more than 1 volt PTP in the LO ports ( 4dBm) and if there is too much drive this results in unwanted mixing product as well as the possibility of smoking them. So I cranked back the PTP input from 1 volt to 500mv as measured under load. The Rx works FB and the Tx seems happy at that level. I also looked at the IRF510 -- man I had that biased really hot! I also added an 50 Ohm swamping resistor on the relay side of the J310's amp that is only active on transmit. This adds a bit of stability to the driver stage input. I am looking at any and all possibilities for what was reported to me. The following video shows the output waveform after the IRF510 amp stage
73's
Pete N6QW
June 24th, 2019 ~ The Main Board.
The following photo is of the mainboard and may assist those who want to build this RADIG with the construction of their project.
Some notes first:
- The Band Pass Filter was on the board from the prior build. You will note that it is called temporary. I strongly suggest building a three section BPF. That schematic is on the n6qwradiogenius.us website. I had to dig around for some cores and that is the next item to be changed out. This was changed today and I will publish the circuit.
- The prior build has some trim pots and these are 100 Ohm (10 turn) units connected to the output of the 74AC74. The center wiper goes to the ADE-1's. I initially set the pots for 50 Ohms at the center and then measured the square wave into the ADE-1 LO Port. I went back and looked at the output and saw with the Si570 versus the Si5351 that I had way too much drive. So the drive has been reduced to a nice square wave about 1 volt PTP for each channel
- Just to the right of the BPF and to the left of the ADE-1's is a hybrid combiner transformer. The core is a type 43 Balun Core with the primary side connected to the output of the BPF and the secondary which is bifilar wound has the common connection to ground and either end is connected to the RF Port on the ADE-1. I tested the idea of using a 100 Ohm fixed resistor across the secondary -- that proved to be not a good idea. So much for ideas coming from EMRFD! The transformer was changed to three trifillar turns of 4 turns apiece. this should give a better impedance match. The number of turns initially are what was on the core from an earlier build-- continuous improvement dictates a change. Stay Tuned.
- The Modem Transformer secondary hot leads are connected to the switching leaf on the DPDT Relay. There are phasing dots on the transformers so that the start primary lead, connected to the ADE-1 is in phase with the start secondary hot lead. The I and Q connections are made to the stereo connectors so that in the NC state the LINE IN from the StarTech Sound Card is connected to that stereo connector and the ADE-1's. On transmit the LINE OUT (speaker) is now steered to the ADE-1's through the NO set of contacts. Keep your line in and line out straight or your RADIG will not work.
June 23rd, 2019 ~ RADIG on the Air!
Breaking News: The Raspberry Pi4 has just been released. More capability and the entry level version with 1GB of RAM still $35. Many new features, bells and whistles. Guess I have to get one. But keep in mind the RADIG IS working with the older RPi2.
Yesterday was amazing with a dozen contacts with the new RADIG. BTW just to clear the air --it is a bidirectional transceiver in that the signal path is switched in/out of the ADE-1's using a DPDT Relay. Had I used Tayloe Detectors, I would need a lot more circuitry. Keep it simple and it works great.
Late photo of new Band Pass Filter and revised Hybrid Transformer
Hopefully others will construct the RADIG -- there is a lot of homebrewing embedded in the RADIG. With just the 2N2219A driver stage connected to the J310's as measured across a 50 Ohm resistor, we see about 250 MW (10 V PTP). There is more than adequate drive for the IRF510.
Some FAQ's:
- Should I take on this project? For most of you reading this blog. -- the simple answer is NO! Taking on the RADIG means you will have to have some skills beyond knowing the ICOM 7300 menu that sets the power output. You will have to feel comfortable in reading schematics, knowing about Ohm's law, understanding how to find components beyond the search block at Amazon. You will have to know how to load software on a Raspberry Pi and even solder (not weld) small components. Understanding circuit layouts and how to avoid feedback paths is also high on the list. Oh did I mention you will not only need some decent test gear but also how to use it. Lastly but not the least --how to think and resolve issues based on data. Like I said not easy!
- Can a Raspberry Pi2 work with the RADIG? The simple answer is yes -- BUT you will use four USB ports to include the I & Q of the Sound Card. The USB Synthesizer, the USB Sabrent Mic/Headphone and the Wireless Keyboard Mouse. So if you want to connect to the Internet (to report WSPR Spots) you have to use the ethernet (wired) port. If you get a RPi3 then you have options such as bluetooth and the on board WiFi port which then enables the RADIG Plus the Internet.
- Is there any difference in using the RP3 or ASUS Tinker Board? The Tinker Board has far greater capabilities at 2X the price. But I have not found an easy way to install WSJTX like in the RP 2 or 3. That darn Tarball just wants to sit there and not install. If I get that figured out will share with you.
- How difficult is it to load QUISK? With the later variants (04.1.40 just released) it is far easier than when I first did this some three years ago. Follow the instructions and you are there in short order.
- Can you use a small 7" HDMI screen with the RADIG. The HDMI I have works better with the RPi3 than with the ASUS Tinker Board. Initially if you set up the screen resolution for the small print (1280 X 720) using a larger HDMI then when you plug in the 7" HDMI Rpi2 or 3--it holds that resolution and you will get all of the QUISK Panel. If you start with the 7" HDMI -- the normal default screen resolution is or less pixels like 600 X 420 --and even trying to adjust that using the screen resolution setup functionality the 1280X720 is not one of the choices. Net result -- you only see 1/2 the control panel. With the Tinker Board using this procedure automatically sets the pixels to the lower value with no options to change it. So if you are looking for compact -- get the RPi3!
- I do not have a CNC --so how do I make the boards? See the W1REX website and you can buy the MeSquares and MePads which can be superglued to a 4X6 PC Board. These will work with this project.
- What will this cost me? Well that depends on how big of a junk box you have. My junk box spans 60 years and so I have lots of parts. But two expensive pieces can be had free -- the ADE-1's and the Si570's can be sampled. The USB Synthesizer --around $15, the RPi3 at $35, the Modem transformers for $4, the 74AC74 for less than $1, the other electronics (cores, wire, J310's, resistors, caps, hardware) about $50 and finally the StarTech 7.1 sound card about $35. You must add in the keyboard/mouse and display. I found that an older LED TV we have has HDMI --and works perfect.
- But it is QRP --who works QRP? Well my long term plan is 600 watts+. But with just the IRF510 barefoot (> 7watts out) I worked into Utah yesterday on the FD Cluster Bang. That was a 500 mile trip. At minimum I plan to add a 45 watt after burner that with the heat sink cost me $25 with shipping. At 45 watts you will not have the QRP frustration once the FD contest is over. With 45 watts you can nicely drive a SB-200to 400 to 500 watts output.
- So I want to work 75 Meters so I can participate in the "old drunk guy net" or I want to work 20 Meters so I can join the 14.208 group that parrots FOX news, how do I do that? I will publish info on Band Pass and Low Pass Filters for these bands and then you will have a choice of three bands. I heartily recommend a plug in filter approach versus a band switched approach as making band switching work without problems is more of an art than science for the average (or less than average) homebrewer. We need only to look at the several iterations of the uBitx to address some of the band switching issues. That was a collective solution and I will not respond to issues dealing with band switching. You will have data on the other bands thus you have to do some of the work!
So get hot and build a RADIG.
73's
Pete N6QW
June 22nd, 2019 ~ On Frequency!
BREAKING NEWS... The RADIG Is "On The AIR". Just made twelve (12) Field Day QRP contacts with stations in San Diego a distance of 170 Miles and Sacramento Valley about 390 miles and even out to Utah from the N6QW Laboratories in Newbury Park. The station in Sacramento said the signal sounded excellent! This is exciting!!!!!
The 2N2219A Driver stage and the IRF510 board are just behind the Raspberry Pi2. Lots of wires but it does indeed work.
This morning I ran a few more tests of the RADIG to see if my frequency calibrations of 6/21 were still valid. I dialed in the 40 Meter FT8 Frequency and Boom this is what I received. Note two things -- it is on frequency or close thereabouts and secondly my J310's configured as a DGM do a creditable job as an RF amplifier ahead of the two ADE-1's.
Today I hope to test the transmit function and that should prove interesting. Stay tuned. That is ZL1LC calling CQ on 40M FT8. So the RADIG will hear more than signals down the block! The time is shortly after 7:00 AM left coast time.
I should also mention my droopy dipole has been upgrade to a height of 33 feet at the apex. Big difference!
73's
Pete N6QW
June 21st, 2019 ~ Calibrating the Dial.
SBRYMH
[Updated 6/22 with info on the USB Synthesizer and Reed Relay Control circuitry.]
If we were building an old school analog radio having the dial off by 3.7 kHz would be no big deal. But with the SDR RADIG it has to be dead nuts on. The QUISK software to my knowledge does not have a means to directly calibrate the Microcontroller and Si-570, so you must take another route.
Luckily on a Windows 10 Computer I had HDSDR installed so I could use my Omnia with the HDSDR. Let me tell you one thing -- for my usage the QUISK is orders of Magnitude easier for me to use. BUT the HDSDR does have a means to calibrate the Microcontroller/Si570.
Using my signal generator (FEELTECH) I pumped in a signal of 7.189 MHz and setting the HDSDR to CW, I centered on that frequency and noted the frequency reading in HDSDR. So we now have what the dial reads and what the generator is pumping out. Another way, if my RADIG Tuned WWV I would be able to lock on WWV and then you have a very accurate signal source --again the key is noting the difference in frequencies. In my case it was 3.7 kHz.
On the HDSDR panel is a button so you can call up a Si-570 utility. One of the Tabs is Calibrate. Thus you simply enter what is what your reading on the RADIG and what is being generated. The you push the "CAL" button and the two are synched to the actual frequency.
I then went back to the RPi computer and sure enough the reading on the dial and the actual frequency are way closer than 3.7 kHz. I will repeat the difference tests using some known frequencies and operations like certain nets and operations like FT8. But a heck of a lot closer than when we turned it on!
I think I may be really close on the calibration as I took a listen to FT8 and WSPR by dialing in the frequencies using the keyboard. I am decoding the signals.
So we will test this for a while
I think I may be really close on the calibration as I took a listen to FT8 and WSPR by dialing in the frequencies using the keyboard. I am decoding the signals.
So we will test this for a while
Started fabricating the relay board as per yesterdays post and I may lift a driver and final board out of another rig so having this on the air may be closer than I thought it would be. Early this evening I finished the relay board and actually it is a unitized assembly including the USB Controller --so nice and tidy.
This a stock piece of perforated board which lets me mount the USB Synthesizer, and Reed relay switching all at one location. There is a three pin header to the left of the relay and these pins are in parallel so that many connections can be made to the board and that was shown in the schematic. Neat and Tidy!.
The Red/Black wiring supplies power to the Reed Relay circuitry. The USB Controller is powered separately from the USB Buss. Although one of the options is to supply power to the USB Controller for a portion of the circuitry via 12 Volts. There is a pin in the lower right hand corner that is where the 12 VDC is connected and you remove Jumper P1 on the board. Just keep things simple and use the USB to power the board as there is more than enough juice on the RPi 2 or 3 to supply the current.
This a stock piece of perforated board which lets me mount the USB Synthesizer, and Reed relay switching all at one location. There is a three pin header to the left of the relay and these pins are in parallel so that many connections can be made to the board and that was shown in the schematic. Neat and Tidy!.
The Red/Black wiring supplies power to the Reed Relay circuitry. The USB Controller is powered separately from the USB Buss. Although one of the options is to supply power to the USB Controller for a portion of the circuitry via 12 Volts. There is a pin in the lower right hand corner that is where the 12 VDC is connected and you remove Jumper P1 on the board. Just keep things simple and use the USB to power the board as there is more than enough juice on the RPi 2 or 3 to supply the current.
Bummer for those who just like to operate --two days of crazy people yelling into an overdriven SSB appliance box radio --CQ FD.
Today is a birthday of sorts for me -- 60 continuous years of being a licensed ham. It also is 42 years as an Extra. Proudly I got my Extra when you had to study and know technical information in addition to passing a 20 WPM code test. You simply didn't get your extra as a bonus offering with a subscription to QST. There were no questions on my exam such as what is the most popular 100 Watt SDR radio from ICOM.
I wonder how many Box Top Extra Hams know what a Foster Seely Detector is used for and how to make one. That was on my Extra test!
73's
Pete N6QW
June 20th, 2019 ~ The RADIG IS ALIVE!
You must be reverent when you watch this video.
SBRYMH!
You must be reverent when you watch this video.
SBRYMH!
A Really Great Milestone Accomplishment!
Using the board originally installed in the rig I built patterned after the work of Charlie, ZL2CTM, I just couldn't wait to give it a smoke test. It didn't smoke; but it sure has exceeded my expectations. The ADE-1's work FB and the USB Synthesizer easily follows the Quisk commands. This is exciting.
This video is of just the receiver and I need to add the relay switching for Line In / Line Out and two more transmit boards and the LPF plus some control circuitry. See the comments in the video about plug in filter boards -- with 20 Meters perking up --a definite on the to do list. But for now landlocked on 40 Meters.
One other task is to calibrate the microcontroller to be dead nuts on frequency --it is off by 200 to 300 hertz. There is a procedure for doing this in Windows and I may have to use another computer to do that task.
Take a look at how little hardware there is to have such great receive and transmit capability. This is the future wave.
So OK how many viewing this blog said --it will never work! Well at least it works on receive and in a couple of days we will be testing the transmitter functionality. So then we will really know.
My future efforts will take on the microcontroller calibration to put it on frequency (you will want this) and then build a couple of the transmitter boards and the Line In / Line Out relay switching and a bit of clean up. This board has a few refinements like the trim pots coming off of the 74AC74 which lets you balance the LO signals to the ADE-1's. That I will detail. But so far very promising.
Very little hardware and lots of performance!
Getting ready for the transmit portion we need to do some preparations. The USB Synthesizer Board has a Pin marked PTT. When commanded by the QUISK Software +5 VDC appears on this pin.
I developed a circuit so that you can take that 5 VDC and switch a relay via the venerable 2N3904. I know you will jump on this--- resist writing me about using power FETs and all other schemes.
This works, I have the relays and some relays are already installed on the board. You are free to do as you like. But please don't give me a technical dissertation on why your method is better. The reed relay has low current draw and the contacts can handle 1 amp. That is all you need to control the items that are used on transmit. Before you write me --see the note on Snubber Diodes on all relays!
So OK how many viewing this blog said --it will never work! Well at least it works on receive and in a couple of days we will be testing the transmitter functionality. So then we will really know.
My future efforts will take on the microcontroller calibration to put it on frequency (you will want this) and then build a couple of the transmitter boards and the Line In / Line Out relay switching and a bit of clean up. This board has a few refinements like the trim pots coming off of the 74AC74 which lets you balance the LO signals to the ADE-1's. That I will detail. But so far very promising.
Very little hardware and lots of performance!
Getting ready for the transmit portion we need to do some preparations. The USB Synthesizer Board has a Pin marked PTT. When commanded by the QUISK Software +5 VDC appears on this pin.
I developed a circuit so that you can take that 5 VDC and switch a relay via the venerable 2N3904. I know you will jump on this--- resist writing me about using power FETs and all other schemes.
This works, I have the relays and some relays are already installed on the board. You are free to do as you like. But please don't give me a technical dissertation on why your method is better. The reed relay has low current draw and the contacts can handle 1 amp. That is all you need to control the items that are used on transmit. Before you write me --see the note on Snubber Diodes on all relays!
73's
Pete, N6QW
Breaking News: USB Synthesizer Works!
The 3.3 VDC regulator arrived and I installed it in the circuit and performed the other checks. Several years ago I downloaded an app from the QRP2000 website so that you can actually produce RF with just this app and a Windows machine. But you also have the special piece of software (also downloaded) so the USB links up with the I2C buss on the Si570. (DG8ASQ )
It looks like this in the above screen shot. The frequency generated is 17.3 MHz and so we should be looking for an output on the output pin of 4X frequency that or about 69.2 Mhz and this is what I saw on my scope. About 450 Mv PTP and at a frequency of 69.2 MHz
Later today as promised I will have some photos of the board itself. The back up soldering iron is crap and so is that lead free solder. I discovered that the Si-570 I had earmarked for this was for a special LV application (wrong). I did have an Si-570 that matched the P/N as in the photos of the install manual; bUT it was on soldered on a board -- almost welded in place. I did carefully remove it and I am happy to see it works in the USB Syhthesizer.
I see that my 3.3 VDC low dropout regulator will be delivered today so I will finish the 1st major section and perform the voltage tests. If that passes then we will install the Si-570 and complete the final testing.
My intent is to provide detailed photos to see how the USB Synthesizer was built. The next phase will be to install some of the hardware on the detector board and perhaps by week end we can do some initial listening tests. I am a bit behind on some of the other hardware builds and so I need to ratchet up the work schedule.
BTW as best as I can determine the RPi3 USB ports can supply 500 ma per port -- so that should not be a problem to power the USB Synthesizer board entirely off of the USB port as the draw is about 100 ma. Now my hammie friends time to add the currents. You have 4 USB ports on the RPi3 and so if you do the maximum draw on the ports --that is 2 amps and you need about 1 amp just to run the RPi3 itself. That is also why you need a heatsink and very likely a fan! So if you do a bit of math that comes to 3 amps.
That is why you should not run your Pi on anything less than a 5VDC, 3 amp supply. That is why they are recommending a 3 amp supply for the RPi3. Ditto for the ASUS Tinker Board. So if you have a 5 VDC supply at 1 amp supply left over from a former phone charger. DON'T USE IT!!!!!!
A project like this can easily go off the rails when you lose sight of the project objectives. Firstly, look up Charlie Morris ZL2CTM on you tube. Charlie has some amazing homebrew tutorials and has built a completely homebrew SDR transceiver using the Teensy 3.5 as the computer source and a special PJRC Sound Codec Board.
I know it works because I built one! That rig also uses the two ADE-1's or SBL-1's as direct conversion receivers. It is not about Tayloe Detectors and a choice to use them or not use them. It is a choice to use the DBM's because they are bi-directional and this minimizes the overall circuitry.
My project objective is to build on Charlie's earlier work only substituting the RPi3 or ASUS or Tinker Board and the Quisk developed SDR software with essentially the rest of what I was using with the Teensy 3.5 and Sound Codec Board. The Quisk has more features and functionality than what Charlie wrote for the Teensy 3.5. Cost wise the RPi3 is almost neck and neck with the Teensy 3.5 Board and true the StarTech 7.1 is about $16 more but the increased functionality is the desirable outcome.
So once I get this working I may entertain some future project with Tayloe Detectors -- I already have four of them mounted on Circuit Boards provided by a good friend --Thanks Bob.
But the immediate approach is with the ADE-1's.
That is why you should not run your Pi on anything less than a 5VDC, 3 amp supply. That is why they are recommending a 3 amp supply for the RPi3. Ditto for the ASUS Tinker Board. So if you have a 5 VDC supply at 1 amp supply left over from a former phone charger. DON'T USE IT!!!!!!
A project like this can easily go off the rails when you lose sight of the project objectives. Firstly, look up Charlie Morris ZL2CTM on you tube. Charlie has some amazing homebrew tutorials and has built a completely homebrew SDR transceiver using the Teensy 3.5 as the computer source and a special PJRC Sound Codec Board.
I know it works because I built one! That rig also uses the two ADE-1's or SBL-1's as direct conversion receivers. It is not about Tayloe Detectors and a choice to use them or not use them. It is a choice to use the DBM's because they are bi-directional and this minimizes the overall circuitry.
My project objective is to build on Charlie's earlier work only substituting the RPi3 or ASUS or Tinker Board and the Quisk developed SDR software with essentially the rest of what I was using with the Teensy 3.5 and Sound Codec Board. The Quisk has more features and functionality than what Charlie wrote for the Teensy 3.5. Cost wise the RPi3 is almost neck and neck with the Teensy 3.5 Board and true the StarTech 7.1 is about $16 more but the increased functionality is the desirable outcome.
So once I get this working I may entertain some future project with Tayloe Detectors -- I already have four of them mounted on Circuit Boards provided by a good friend --Thanks Bob.
But the immediate approach is with the ADE-1's.
73's
Pete N6QW
June 18th, 2019 ~ More RADIG Construction Notes!
SBRYMH!
Firstly another friend down in VK Land shared his favorite hat and I will now share that with you
For those of you who are under 35, the year 1984 is older than you are. George Orwell wrote a book called 1984. The book was written way before 1984 and it was a look into the future where people were subjects of a future state where freedom was very limited.
The hat suggests we are in the state of 1984 and we need to return to where the actual is not that; but purely fiction. It is sort of like the emperor (small e) is today hinting he will start deporting millions of undocumented immigrants starting next week. Wow does he realize some of his prime business properties will be impacted.
A comment was made about the matching transformers I suggested using to interface between the ADE-1 and the 600 Ohm Modem transformers. I simply looked at a 50 Ohm to 600 Ohm match which resulted in in a 4 turn to 14 turn winding and the 12:1 impedance step up transform. The comment raises a significant point about the actual frequency range (read audio and not RF) and that the inductance values are too low for the audio range.
Let's look at some math. The classic formula for inductive reactance is Xl = 2*pi*F*L. If we say pick 3000 Hz as the F in this formula and we also say pick Xl as 50 Ohms then the unknown is L which is 2.65 mHy and if we repeat that for 600 Ohms then the L results in 31.8 mHy. These are quite large values for a FT-37-43 core that result in a lot of turns. If we use the Al value for the FT-37-43 as 380 (from Amidon) then our 2.65 mHy winding is 83 turns and our 31.8 mHy winding is 289 turns.
So lets check our math --the impedance transform is based on the Turns Ratio squared. So 83^2 = 6889 and 289^2 = 83251. If we 83251/6889 then that does give us 12:1. Thus the posted comment tells us we need to consider the frequency which drives the inductance values for the impedance transform. At this point I am not sure how to build a 289 Turn winding on a FT37-43 core. So we may have to look at some other cores or other forms of matching. A good comment and a good mathematical exercise.
Now I have to find a better solution which will start first at looking at a capacitive matching scheme. For 3 kHz, the capacitive reactance at 600 ohms is 88.3 Nano Farads and at 50 ohms is 1060 Nano Farads. So a series combination of capacitors that equals 88.33 across both caps and 1060 Nano Farad across the tap would yield a match. Capacitors in series are like inductors in parallel. Thus a combo of a small capacitor and a large capacitor yields a total value smaller than the smaller capacitor. If that second capacitor was 96 NF and the larger a 1060 NF --the series would yield 88 NF and the tap point to ground 1060 NF. The closest standard values would be 100 NF (0.1 uFd) and 1.1 uFd (1100NF). So that is worthy of a look as these values would be less than 3 kHz which should be OK
Now I have to find a better solution which will start first at looking at a capacitive matching scheme. For 3 kHz, the capacitive reactance at 600 ohms is 88.3 Nano Farads and at 50 ohms is 1060 Nano Farads. So a series combination of capacitors that equals 88.33 across both caps and 1060 Nano Farad across the tap would yield a match. Capacitors in series are like inductors in parallel. Thus a combo of a small capacitor and a large capacitor yields a total value smaller than the smaller capacitor. If that second capacitor was 96 NF and the larger a 1060 NF --the series would yield 88 NF and the tap point to ground 1060 NF. The closest standard values would be 100 NF (0.1 uFd) and 1.1 uFd (1100NF). So that is worthy of a look as these values would be less than 3 kHz which should be OK
I soldered up all of the connections on the board less the two regulators and NOT the Si-570 (as per the directions). So we are awaiting the delivery of the 3.3 V regulator.
There is some initial testing that must be done prior to installing the Si-570. If there is an error --you don't want to smoke the Si-570. Thus terribly important to RTM and follow the directions
There are several options for powering the board and the board is fitted with those options -- the easiest is to simply power everything off of the USB port. But as the instructions so note -- that is a large draw current draw on the RPi3 USB port.
You next have a combo of powering some things off of the USB (Si-570) and the rest of the circuitry from a 5 VDC supply Or even a 12 VDC supply. Thus the options are USB only. or USB with 5 VDC or USB with 12 VDC.
There is a two pin jumper (jumper also supplied) that is engaged for powering all from the USB. I also added a two pin jumper so you could plug in 5 VDC to power the circuitry other than the Si-570. I need to affirm the current limitation on the RPi3 USB ports and so this is an item to be checked.
I will also be researching a better matching scheme. I think it is very important to have this matching in place and needs some further research. Any ideas or suggestions let me know.
Finally a bit of Pasta Pete here..
73's
Pete, N6QW
June 17th, 2019 ~ Back to the RADIG!
I wanted to share one of my Father's Day gifts from the kids.
SBRYMH!
My kids would never think of getting me a MAGA hat as that symbolism has very negative connotations with the person who espouses that saying. However it is appropriate to recognize that wearing a Camo Style Hat with an American Flag is what made America Great! Having served in the US Military with two trips to Vietnam I am proudly wearing my truly Made America Great Hat! No bone spurs here!!!!
I have heard that the USB Synthesizer kits are being restocked and will be available at the end of June. We must have caused a run on their stock. BTW --this is in the realm of superb customer service. Jan at SDR-kits after I alerted him about the regulator problem and actually asking about substitute parts --said hey we will send you out a replacement. (The part cost $0.96.) I told him No as I had ordered some spares an they are already being shipped from Digi-Key --another great customer service company.
Later today I hope to install more parts on the board bypassing the regulator install sequence until I get the proper regulator. Today's work will involve the pin headers and power connection posts. I also hope to install the 4:14 turn broad band transformers that interconnect the ADE-1's and the 600 Ohm Modem Transformers. BTW I got my free ADE-1's last week.
Every time I speak or write the words broad band I think of Ina Ray Hutton and her all girl orchestra who were very popular in the 1930's. One of their specialties was jazz -- with that in mind broad band take on a whole new different meaning.
Later today I hope to install more parts on the board bypassing the regulator install sequence until I get the proper regulator. Today's work will involve the pin headers and power connection posts. I also hope to install the 4:14 turn broad band transformers that interconnect the ADE-1's and the 600 Ohm Modem Transformers. BTW I got my free ADE-1's last week.
Every time I speak or write the words broad band I think of Ina Ray Hutton and her all girl orchestra who were very popular in the 1930's. One of their specialties was jazz -- with that in mind broad band take on a whole new different meaning.
A publicity photo of Ina Ray Hutton. Check her out on Wikipedia.
73's
Pete N6QW
73's
Pete N6QW
June 16th, 2019 ~ Family Visit Day. No work on the RADIG
It is really important to check your parts list and the hardware before you start building -- I am about 85% done only to discover that my kit had two 5 VDC TO-220 regulators instead of one 5 vdc and one 3.3 VDC. So I will be delayed a couple of days until the special regulator shows up -- the 3.3 VDC Low Dropout one.
Now I did check to make sure I had all of the caps and right resistors and when it came to the devices I just said "yeah there they are". It is when I went to put the parts on the board is that I realized that the parts had different markings (like from two different manufacturers) but the numbers were the same.
I have included some shots of the WIP so far and as you can see the transition from just the caps installed on the underside to more parts being added topside.
BTW my usual soldering iron from XY Tronic broke (stopped heating) and so I switched over to the backup that I bought from Marlin P Jones. Were the Radio Gods telling me I had to have a more positive view about the kids coming over today and the result was no work on the RADIG. Never fool with the Radio Gods!
Pete, N6QW
June 15th, 2019 ~ A RADIG Respite!
The posting for today is to give those of you who are working along with me on the RADIG --- a chance to come up for air.
Hey Look At This -- FT8 on the SoftRock V6.3 with Raspberry Pi3. I was running 50 watts on 20Meters.
Hey Look At This -- FT8 on the SoftRock V6.3 with Raspberry Pi3. I was running 50 watts on 20Meters.
First I would like to share with you a QSO I had yesterday afternoon on 75 Meters using a rig that was totally homebrew, totally designed and totally built by me. Yes I dusted off the KWM-4 which you can see on QRZ.com.
Later on after this QSO I did check in to the Vintage Collins SSB net on 3.895 MHz. I got excellent signal reports and must tell you my dial (and frequency stability) is more accurate than the several S Lines and KWM-2's that participated. Some even had my QRZ page open while the net was on. Some mentioned remembering prior check ins by me with the KWM-4. Sometimes it is nice to be the lead dog as you get to see more of the scenery.
Back to the 75M QSO ... W6CC was running a homebrew SSB rig first described in a 1947 issue of QST. It was an LC Filter rig, with the filter centered on 18 kHz and made from 88 MHy telephone toroids. The other station, K6TWO was using the Sun SDR MB-1 (read $6K +). The other two stations were in the San Diego area (Santee) and so the path was about 170 miles on 3.893 MHz. I marveled as that QSO had all of the elements of something old, something new, something bought, something homebrewed. It was a delight to see various technologies with one common purpose -- just having fun communicating with other fellow hams. It was pure joy.
So OK I bought a Elecraft K4! The very latest SDR transceiver from Elecraft. The cost was about $4000. Are you shocked? Well get unshocked -- I didn't actually buy a K4 but I did unexpectedly have to spend $4K, the price of a K4, fixing my XYL's teeth.
Yes I have dental insurance; but she broke a bridge that was installed less than a year ago after attempting to crack a piece of See's Candy California Dark Chocolate Brittle using her back teeth as the cracking mechanism. The insurance company ruled --this one is on you. Just to make me feel better in the Memo area of the check I wrote Elecraft K4.
But while I was in the waiting room as the bridge was being installed I spotted the June 2019 issue of Boy's Life magazine --you know the magazine for Boy Scouts.
The first curious thing was that there were three YL's on the cover and no "boy scouts". So as I was perusing the pages which are mostly advertisements (much like QST), I spotted this page.
Ham radio right in the pages of Boy's Life! Also note that the Scout leader is a YL and it appears that three out of the four young people are also YL's. Is there a message here? Evidently there is a Radio Merit Badge and for you "No Code" amateur extras who got your ticket with a subscription to QST -- the Morse Code on the Badge say BSA.
The "rig" in the photos look much like a piece of WWII war surplus. I guess Boy's Life didn't think to contact ICOM so they could photoshop an IC7300 into what I think is a cartoon type drawing. Nonetheless there is some promotion of our hobby outside of the adverts in QST.
Time for more rest. Bummer no playing with radio for the next two days while I get prepared to celebrate Father's Day. Two of the four kids are coming over so that will be fun.
73's
Pete N6QW
[See the end of today's thread for a suitable set of non-magnetic tweezers. This was provided by a good ham friend, Bob, who first puts a bit of solder (light coat) on one of the pads and then uses the tweezer to hold the part in place while then heating the pad. This will temporarily hold the part while you solder the other side and then you swing back to the first pad and apply a proper amount of solder. Thanks Bob!]
I soldered in the capacitors noting C4 is the one that is 1nF and all else are 0.1 uF. The soldering process all 22 connections were done with some breaks --- I did have a cup of coffee and did think about Mary Jane Schwartz and that 1966 Red VW.
The soldering turned out so, so OK; BUT not as good as when I could spot a 44DD from a mile away. Having the Vellman Headband Magnifier sure helped. Now notice in the top photo I have some aluminum (or aluminium as some would say) spacers that will come in handy when you turn the board over and have to insert the through hole parts on the board.
So now I am ready to proceed with other soldering; but not today. Again the idea of the cookie tray --- I simply place the instructions on the top of the tray covering the parts, tools and WIP (sorry an old aerospace term for Work in Process). The tray is neatly put away in a safe place ready for the next work session.
As I mentioned in yesterday's posting I hoped to have some photos from my friend Greg in VK land of his SMD hold down tool. Feast your eyes on this jewel. This is definitely "uptown" from my mechanical pencil approach. It looks like most of the parts can be found either at Home Depot or Lowe's maybe DIY Hardware.
In fact you can buy the lumber and some of the other parts at a cool place called JOANN Fabric's or Michael's art supply also. So for those of you who want to be 'inclusive" suggest to your XYL, Partner or Significant Other that you will take them to JOANN fabrics and while they are "looking around the store" slip over to the area where they keep the art supplies and you will find finished 1/4' plywood cut to almost the exact size and ditto for the Rubber bands. JOANN Fabrics also sells better than Exacto knives at less cost!
Greg writes:
The
rig is extremely rough and ready, but works a treat.
I think the only things new on the jig are the pcb in the shots and the 1206 size capacitor being held down. The rubber bands were wrapped around some mail that arrived. I've used it on components down to 0603 size, but frankly the tip is a little large for that. I'd probably shave it down some more if I was using 0603 regularly.
The arm portion can be made from any relatively stiff bit of wire (I used a cut off of aluminium welding filler rod). I did the bending by hand. It is bowed in the middle from my initial set up, when I had far too much tension applied via the rubber bands. This bow is completely unnecessary. 😂
The jig originally had another piece of wood underneath at the front, but I used some really cheap glue and it fell off after only a couple of years. I had a bunch of the little spring clamps, so I just use a couple on the front edge to provide that support. One day I'll get around to re-attaching a piece of wood. Probably after I finish everything else. If I was doing it again I wouldn't bother with these feet - they were a waste of time, and were actually only intended to add some weight. That didn't turn out to be necessary.
To give a rough idea of the dimensions the PCB in the picture is 100mm long by 75cm wide
I think the only things new on the jig are the pcb in the shots and the 1206 size capacitor being held down. The rubber bands were wrapped around some mail that arrived. I've used it on components down to 0603 size, but frankly the tip is a little large for that. I'd probably shave it down some more if I was using 0603 regularly.
The arm portion can be made from any relatively stiff bit of wire (I used a cut off of aluminium welding filler rod). I did the bending by hand. It is bowed in the middle from my initial set up, when I had far too much tension applied via the rubber bands. This bow is completely unnecessary. 😂
The jig originally had another piece of wood underneath at the front, but I used some really cheap glue and it fell off after only a couple of years. I had a bunch of the little spring clamps, so I just use a couple on the front edge to provide that support. One day I'll get around to re-attaching a piece of wood. Probably after I finish everything else. If I was doing it again I wouldn't bother with these feet - they were a waste of time, and were actually only intended to add some weight. That didn't turn out to be necessary.
To give a rough idea of the dimensions the PCB in the picture is 100mm long by 75cm wide
Thank You Greg --absolutely superb! I am awaiting to hear from the Dental Pick lady and if she responds I will show that tool as well. It is not unlike Greg's approach.
Weekend coming up and here in the US it is Father's Day. Somehow my kids are ignoring my special Father's Day request. I asked that I be left alone for about 4 hours so I can finish up soldering the USB Synthesizer Board -- they thought I was kidding them! Bummer is a good word.
73's
Pete N6QW
June 13th, 2019 ~ TKT --- This is shorthand notation for Tribal Knowledge Tips.
SBRYMH!
For some reading this blog this may be a first time for building a RADIG and probably for most, the 1st time for a major soldering project involving surface mount components.
We have all experienced first time events like riding a bicycle or parking an automobile or perhaps Mary Jane Schwartz in the back seat of your 1966 Red VW Beetle. Clumsy, awkward and never to be forgotten are words that come to mind.
So today I want to cover some TKT that may make that 1st time experience a bit more enjoyable.
Firstly and whilst in an unsoldered condition take the small circuit board provided with the SDR-kits and after assuring it is topside up trace the three mounting holes on a piece of scrap PC Board that is the same size as the SDR-Kits Board. See the photo below.
After tracing the three mounting holes drill them out. You now have a drilling template for later when you will go to mount this board in the enclosure. By making it the same size you also have a "fit check" tool. [See what you learn when you work in aerospace manufacturing.]
Like we used to say "it does not have to be precise BUT close enough for government work". This is my drilling template.
Like we used to say "it does not have to be precise BUT close enough for government work". This is my drilling template.
This template also reduces the risk of damaging the USB Synthesizer board trying to use the finished board as the template. Remember the Si-570 gets mounted on the underside of the Board. When you go to fit the completed board in the final box after using the drilling template--you will exclaim: "N6QW truly is a Radio Genius!"
While you are at it, time to find some aluminum spacers (1/2 Inch -- three of them ) that are tapped for 4-40 screws and you will need six 1/4" , 4-40 screws.
Next I want to cover the handling and soldering of the SMD parts which are mostly capacitors and of course the Si-570. Firstly a mention about the Si-570 (only install it when told to do so in the install directions) --it has 8, yes 8 connect points. Three on each side and one at each end. The end ones are the most challenging. Orient the Si-570 per the instructions --it is nearly impossible to get off the board if installed backwards. This is where a fine tipped point installed on a temperature controlled iron is critical. Take your time.
The author of the install instructions suggests the use of tweezers and exercising care in handling the parts as they can become flying missiles. There are 11 caps that must be soldered so that is 22 connections plus the Si-570 means that you will need to make 30 SMD connections. Take your time --you can do it.
I mentioned that most of my tools seem to have become mysteriously magnetized. This includes my tweezers which are kind of useless for precision holding of parts . So if you are going to buy tweezers find ones that are stainless steel as they tend to be non-magnetic. At one time I sold industrial magnets and usually they were encased on the sides not needing to be magnetic with stainless steel. That is why I know that fact.
So how do you hold down the parts while soldering surface mount. I suggested the use of a mechanical pencil --mainly because I have learned how to do that. I also practice what you are taught in "sniper school" control your breath while shooting or soldering SMD components!
But this morning I received an email from a good friend in VK land, Greg who suggested the use of some shop aids to hold down the surface mount parts while soldering the parts to the board. He will be sending me some photos of the tool he uses and he also provided me a link to a tool made from a dental pick used for cleaning your teeth. I need to contact the person with the dental pick for clearance to show her tool. So you will have to keep reading the blog.
However John W5DIA did share a SMD part hold down tool that looks like this below. A trip to Home Depot or Lowe's or DIY Hardware should yield the necessary parts. Or if you are a plumber or HVAC guy for your day job, then the parts are on the truck. This design uses a fine probe at the end to "stake the part" down to the board while at the same time the weight of the brass fittings and copper tubing make it "stay put" while the outriggers provide a high degree of stability.
I will add photos of Greg's tool and once I get permission the Dental Pick, rubber band and woodblock tool. Greg reminded me of this and I seem to remember seeing a similar tool in a back issue of SPRAT magazine. It was made out of some scrap wood pieces and I am bit fuzzy on this but at the time thought it looked like a guillotine. It had some rubber bands in there too. Tony if you are reading the blog --help me out.
I cannot over talk the need to read and re-read the install instructions and to do work in small increments. Make a few connections, take a break, get a cup of coffee and drift back to thinking about Mary Jane Schwartz in the back seat of that Red 1966 VW Beetle.
Previously I mentioned about getting some 1208 sized parts (these are big) and are good to learn the "how to". The smaller sized 805 parts are what is in the kit --so YOU don't want to start off with those. Even if you are experienced in SMD construction --it has been a while since I last built something in SMD so a little practice for me is mandatory. I am going to practice with the 1208 --just to get the brain waves aligned.
Here is a sample of my practice piece. I have lost the touch! Hopefully with more practice I can improve. The 1 was initial test. Now what makes this a bit harder is the new solder . It is difficult to work with when using it with a large heatsink area. The 3rd application is showing some improvement --but still a bit too much solder being applied, but less than welded parts.
Here is a sample of my practice piece. I have lost the touch! Hopefully with more practice I can improve. The 1 was initial test. Now what makes this a bit harder is the new solder . It is difficult to work with when using it with a large heatsink area. The 3rd application is showing some improvement --but still a bit too much solder being applied, but less than welded parts.
The install instructions mention good lighting, I have a desk lamp right over the work tray AND I also use a headband magnifier. If you are over 30, you need the magnifier. Recently I went to the eye doctor for an eye exam. The Doc asked about my vision --I said terrible. He looked surprised and asked what did I mean. Well I said I used to be able to spot a good looking woman (read 44DD) about a mile away and now the range is down to 1/2 mile. He did not know how to process that information and probably you don't either --sorry guys it is an Italian thing.
Well you have enough TKT for today and I will update this section with additional hold down tools. Try to keep up.
73's
Pete N6QW
June 12th, 2019 ~ More Build Stuff
SBRYMH = Start By Removing Your MAGA Hat
SBRYMH = Start By Removing Your MAGA Hat
SBRYMH!
Yes you will have to do some surface mount soldering! Get over it as that is the new technology! But go slowly and ditch your old habits of "welding" electronic parts to circuit boards. You will also have to contend with the new solder that is real crap!
Yes you will have to do some surface mount soldering! Get over it as that is the new technology! But go slowly and ditch your old habits of "welding" electronic parts to circuit boards. You will also have to contend with the new solder that is real crap!
There are some things you should do in advance of actually working on the USB Synthesizer Board. The first is to acquire some surface mount parts like the 1208 size capacitors and the using a piece scrap PC Board --- learn the how of keeping parts in place and how to have the iron at just the right temperature and to flow the solder.
Jack Benny a long ago forgotten comedian (and accomplished violinist) of the last century told of a chance meeting with a young lad in downtown Manhattan. The young lad asked how he could get to Radio City Music Hall. Benny in his usual dry humor said without batting an eye: Practice, Practice, Practice! For those of you who removed the MAGA hats you will undoubtedly get the message.
A couple of other tools you will need to successfully solder in place( at the right place) SMD parts. One is some masking tape and the other is a Pentel 0.5 mm mechanical pencil with HB lead. The masking tape is to hold the PC board down to the work surface during the soldering process and Pentel Pen is to apply gentle pressure on the part while you solder.
I don't know about you --but most of my metal tools seem to mysteriously have been magnetized and are useless working around SMD parts. The Pentel Pen with the soft lead is immune to being magnetized. The holding down of the part while soldering is another skill that comes with practice.
So you have some homework! If you are not skilled at soldering SMD parts do not skip the practice part with the 1208 size caps and scrap PC board!
Stay tuned for more exciting adventures with the SDR RADIG. Oh be sure to visit SDR RADIG Website There is info there that is not on this blog --see I am forcing you to look at more than just the blog. When you are the driver --- you do get to steer the car!
Take a careful look at this schematic (that is something you will also have to learn) and look closely at the different capacitance values. There are some 0.1 uF and some 1 nF. Don't mix those up and perhaps you didn't know 100 nF = 0.1 uF.
So the net result if you do mix those up is that in one case you might only have 1/100 of the capacitance needed or 100 times too much capacitance. Let's see was any of that covered on the current Amateur Extra Exam right along with Name a Popular ICOM Transceiver. Tough questions...
Carefully read the build instructions as they describe the sequencing of parts installations. The bottom side of the board is done first with a special note about C4 being that pesky 1 nF cap and DO NOT INSTALL the Si-570 at this time. Everything installed on the bottom side is surface mount!
The follow on instructions describe the installation of the top side parts which are all through hole. These instructions are just like the Heathkits of old. Install parts and check off! Finally you will be told when to install the Si-570. Do Not Be in a Hurry!!!!!!!!
Take a careful look at this schematic (that is something you will also have to learn) and look closely at the different capacitance values. There are some 0.1 uF and some 1 nF. Don't mix those up and perhaps you didn't know 100 nF = 0.1 uF.
So the net result if you do mix those up is that in one case you might only have 1/100 of the capacitance needed or 100 times too much capacitance. Let's see was any of that covered on the current Amateur Extra Exam right along with Name a Popular ICOM Transceiver. Tough questions...
The follow on instructions describe the installation of the top side parts which are all through hole. These instructions are just like the Heathkits of old. Install parts and check off! Finally you will be told when to install the Si-570. Do Not Be in a Hurry!!!!!!!!
73's
Pete N6QW
June 11th, 2019 ~ USB Synthesizer Build
Every successful build starts with organization of the build. In other words if you fail to plan, you plan to fail. Take a trip to your local Dollar Store or maybe even your Winn Dixie or Piggly Wiggly supermarket (maybe even an Aldi's) and locate where they sell pots and pans. Find an inexpensive "cookie sheet" typically around 10X16 inches in size. Buy it.
This is a capture tray where you will work to fabricate the USB Synthesizer interface. I usually place a white paper towel as a bottom liner so you can easily see the parts against the white background. This tray is a "must have" if working with SMD parts!
You will use this tray to open the bag of parts and inventory what is in the bag versus what is stated in the Bill of Material. You did of course download the manual as you were directed and have the BOM handy. You will also need that DVM to measure the resistance values so you put the right resistors in the right through hole. Hopefully you have some high quality needle nose pliers and a pair of "nippers". Your new temperature controlled soldering iron of course has been set up too. Solder wick, solder and an Exacto knife round out the tool set. You will also need some "medical grade" tweezers (something better than you would buy from Harbor Freight)!
The other advantage to the tray is that you can simply pick up the tray, and move it to a safe location and then return to the work at some later time. BTW in one of the photos is a small silver square -- that my "hammie" friends is the Si-570. In the last two photos you will spot the very fine tipped soldering iron tip. That is why you need to rid yourself of the Radio Shack 80 watt part welder/burner.
Yes you will also have to solder in a bunch of surface mount caps.
The other advantage to the tray is that you can simply pick up the tray, and move it to a safe location and then return to the work at some later time. BTW in one of the photos is a small silver square -- that my "hammie" friends is the Si-570. In the last two photos you will spot the very fine tipped soldering iron tip. That is why you need to rid yourself of the Radio Shack 80 watt part welder/burner.
Yes you will also have to solder in a bunch of surface mount caps.
73's
Pete N6QW
June 10th, 2019 ~ USB Synthesizer cont'd
Our USB Synthesizer when used with PowerSDR software (or
Rocky) allows you to set the LO frequency to x4, so the
frequency generated is 4 times the Receive frequency displayed on the LCD, hence perfect to use the 74AC74 to generate
quadrature LO signals.
Below is the wiring diagram of the 74AC74 and how the signal is taken from the USB Synthesizer and turned into two square wave frequencies 90 degrees out of phase and 1/4 of the value.
BTW a ham once commented that if you used this same process (divide by 4) with the Si5351 that you would get a 6dB improvement in the phase noise 10log(4) = 6. Thus if you need an LO frequency of 23 MHz then you would actually generate a signal at 92 MHz and then run it through the 74AC74.
Do a little research and you will find some D Flip Flops that work to 300 MHz --good enough for the 4 Meter Band. You will also need the Si570 version that works to 900 MHz --so don't get too excited --the stock CMOS ones work to 160 MHz.
I have done the 4X with the Si535 and the code modifications also require that you modify the step tuning rate so that when you increment by 1 --it is not 4. Essentially you generate the frequency at 4X run it through the 74AC74 and out comes the LO frequency needed. Charlie Morris, ZL2CTM in his SDR work added a simple statement in his code that when you set the Si5351 output you add code so that the result needed is 4* that frequency but you display the frequency generated. The issue is that if you do not divide it down and use it as is then you have the step increment being 4X unless you also modify the step tuning rate.
Below is the wiring diagram of the 74AC74 and how the signal is taken from the USB Synthesizer and turned into two square wave frequencies 90 degrees out of phase and 1/4 of the value.
BTW a ham once commented that if you used this same process (divide by 4) with the Si5351 that you would get a 6dB improvement in the phase noise 10log(4) = 6. Thus if you need an LO frequency of 23 MHz then you would actually generate a signal at 92 MHz and then run it through the 74AC74.
Do a little research and you will find some D Flip Flops that work to 300 MHz --good enough for the 4 Meter Band. You will also need the Si570 version that works to 900 MHz --so don't get too excited --the stock CMOS ones work to 160 MHz.
I have done the 4X with the Si535 and the code modifications also require that you modify the step tuning rate so that when you increment by 1 --it is not 4. Essentially you generate the frequency at 4X run it through the 74AC74 and out comes the LO frequency needed. Charlie Morris, ZL2CTM in his SDR work added a simple statement in his code that when you set the Si5351 output you add code so that the result needed is 4* that frequency but you display the frequency generated. The issue is that if you do not divide it down and use it as is then you have the step increment being 4X unless you also modify the step tuning rate.
OK so we are good to go since I am using the SoftRock V6.3 with Quisk 4.1.39 which also requires the 4X LO signal. Glad my brain awakened me and I now will proceed with the build knowing we are on firm ground.
As a reminder --download and study the manual for the USB Synthesizer so you will feel very comfortable in the build. BTW the resistors are close tolerance, thus have additional markings on the bodies. The manual strongly suggests measuring each resistor with an ohmmeter. Do that step! Time to get rid of that bargain $4.95 meter you got at a flea market. Good quality DVM's can be had for around $25.
73's
Pete, N6QW
June 9th, 2019 ~ The USB Synthesizer Build!
[A bit of radio trivia --two companies who formerly built ham radio equipment will soon be part of an aerospace giant in a merger to take place in 2020. So Ok if you own a piece of Collins gear or a Sideband Engineers SBE33/34 those are the two companies. Collins who was acquired by United Technologies and just before its demise as ham gear manufacturer Raytheon bought SBE. So the new company will include United Technologies who will sell off Carrier Air-Conditioning and Otis Elevator has now acquired Raytheon. Once the merger is completed they will be second to Boeing in terms of aerospace clout. Yes I use to work for what is now Boeing. More Trivia Hallicrafters was bought by Northrup before it became Northrup Grumman.]
I have several strange maladies including FFTE (Fat Finger Typing Errors) and another that my brain works while I sleep. Typically I will be awakened by my brain about 3:00 AM either with a solution to a problem or that there may be a problem arising from a faulty analysis.
Well this morning at 3:00 AM it was the faulty analysis -- but it also gave me a solution. I have often talked about that the LO frequency must be generated at 4X and then using a D Flip Flop this causes a frequency divide by 4 and produces two quadrature signals. In my haste to get this project lit off I have stated that we will simply dump the outputs of the USB Synthesizer board into the I & Q channels. My brain while I slept told me we would still need the 74AC74. Dual Flip Flop.
We are going into some "heady stuff" so time to remove your MAGA hat as this requires a great deal of oncentration (concentration is the word, see FFTE is at work). BTW has anyone ever seen a photo of Pence with a MAGA hat on his head. Just curious?
To get a better grounding in where we are headed do an internet search on the Softrock V6.3. There is some amazing documentation on this board that is no longer being produced but the info is solid. Here is a page from that site.
Essentially this the Receiver section and there is a similar page for the Transmit section. There are three components to this schematic. The LO Generation (this is a later board as it uses a PIC Microcontroller in lieu of the ATTiny 45) produces an output at 4X and this is run into the 74AC74 that actually produces two sets of LO signals in quadrature. We will need only one as the 2nd set for the V6.3 fed the transmitter. Since we will be using the ADE-1 on both receive ad transmit -- no second set is required.
Finally is the Tayloe Detector that is followed by two OP Amps to amplify the I & Q channels. We will simply use the ADE-1.
So our Detector Board will look like this.
In the lower left hand corner we will get the signal from the USB Syhthesizer and that is run into the 74AC74. If you look on the schematic there are two 10K resistors on the input side and you can see those in the photo. Now save yourself some grief --use a 14 pin socket with the machined pins (All Electronics) and then using #30 wire wrap wire then wire the socket before soldering to the board. You don't see any wiring in the photo because it is all underneath the socket.
I will provide a separate wiring diagram of the socket so you can see first hand how to do it --will also incldue some photos.
There is a healthy 5 Volt regulator on the board --don't use a TO-92 style but the TO-220 --it gets warm. The quadrature LO is fed to the ADE-1's. Now in one variant I actually used trim pots so that there is a balanced LO signal to each ADE-1. We may have to circle back on that one.
Now as to matching --the ADE-1's are 50 Ohm port devices and we are connecting that to a 600 Ohm to 600 Ohm Modem transformer. I initially used a 100 UFd. electrolytic cap --this is audio at this point. But in keeping a purist approach to this project, a broad band transformer would provide a more precise match. A 50 Ohm to 600 Ohm interconnect would require a 12 to 1 match. So if we wound a 4 turn primary and a 14 ohm secondary --we would get 196/16 = 1:12.25 close. But a 9 turn to 31 turn would inch you closer 9^2 = 81 and 31^2 = 1:11.86. With careful winding 31 turns of #26 will just fill a FT-37-43 core.
Considering no mathcing, the 4 to 14 truns is good enough for government work. I took a bit of time on the matching as this seems to a be a black hole for many hams.
So with that behind us --give me a couple of days to organize the build of the USB Synthesizer and so you must wait until the next chapter is written. It is OK to now put your MAGA cap back on your head.
73's
June 8th, 201 ~ Back to RADIGS
It is hoped you survived Doughnut Day and my good friend, N2CQR told me the official explanation of the term Doughboy, referring to US Military personnel in WWI, dates back to the 1840's and the US Mexican War. [Gee they must have been fighting over Tariffs. ]
It seems like the US Forces while carrying on the fight would get covered in the adobe dust that is prevalent in the southwest. Thus the word adobe became "Americanized' to doughby and later doughboy. Now you know.
Time to remove the MAGA hat so you can absorb more information on the project. Trapping the body heat under that hat impairs reasonable brain functioning.
By way of review, essentially we will be building two direct conversion detectors, used both on transmit and receive that have their signals out of phase by 90 degrees. Our project will use several commercial building blocks such as the Raspberry Pi3B+ (you can use that old RPi2 but if you have to buy one, get the latest), the StarTech 7.1 USB Sound Card, the Sabrent USB Sound Dongle, and the SDR-Kits USB Si-570 Synthesizer board. This will cost you roughly $100. Of these, the SDR-kits will require assembly; but it is a through hole assembly with only one SMD part to attach to the board and that is the Si-570.
To this we will add the "homebrew" stuff like the detector board, the bi-directional amplifier block (J310's), the transmit driver stage (2N2219) and the low level final amp (IRF510). Along the way we will add switching and control circuits.
BTW my modem transformers arrived yesterday --nice and compact.
As indicated earlier I will start the building portion by assembling the SDR-kits USB Si-570 Synthesizer board. Now is the time to start thinking about soldering and soldering irons.
The very 1st thing I want you to do is to throw out that 80 Watt Radio Shack soldering iron --you know the one with the frayed cord and the one that not only welds parts together but burns them in the process. You will require a precision iron to do fine soldering work.
You must use a grounded type, temperature controlled fine point soldering iron. Don't start the project unless you have one! Read about $50. One of the better ones is made by HAKO and it has been private labeled by Circuit Specialists and Marlin P Jones. Do a search on Amazon for this type of iron. Because of the close tolerance parts that will need to be soldered like the Si-570 and the ADE-1's this drives the use of such an iron.
Because you must do a lot of concentration while soldering these parts --yes, no MAGA hat while soldering!
Stay Tuned.
This is crazy, I just looked up Fry's Electronics as they were a good source for Tinker Boards and Raspberry Pi's -- and yes they have some really good pricing on extra fine Solder Wick.
But this is what is on sale today!!!! (My Pasta Pete side is showing!) Yes my Hammie Friends Fry's is selling Hand Crafted Sandwiches --No joke. It is only 7:30 Am and my mouth is watering. Just may have to tell the XYL I need to go to Oxnard to pick up some "ahemmm" Solder Wick.
This is crazy, I just looked up Fry's Electronics as they were a good source for Tinker Boards and Raspberry Pi's -- and yes they have some really good pricing on extra fine Solder Wick.
But this is what is on sale today!!!! (My Pasta Pete side is showing!) Yes my Hammie Friends Fry's is selling Hand Crafted Sandwiches --No joke. It is only 7:30 Am and my mouth is watering. Just may have to tell the XYL I need to go to Oxnard to pick up some "ahemmm" Solder Wick.
Pete, N6QW
June 7th, 2019 ~ National Doughnut Day
Just so you are well informed, today is National Doughnut Day here in the USA and it is believed that some shops are actually giving away free doughnuts. So did you get yours?
Based purely on hearsay evidence I understand that if you live in certain mid-western states and wear your MAGA hat into designated doughnut shops that you are entitled to two free doughnuts. This is so you can bulk up to 239 pounds.
Does anyone know the real reason why US military service personnel were called 'doughboys" in WWI. There are many theories advanced such as using white flour to polish their brass buttons (I used Brasso.)
Just a short infusion of information about my military service experience. At my last duty station (Port Hueneme) I had a collateral duty as the Regimental Legal Officer. My assignment frequently required interfacing with the Naval Investigative Service (NIS) now NCIS. Of course NCIS today is a highly popular TV series soon to start season 17. In 1967 there were a lot of issues with drugs including some being smuggled back into this country from South Vietnam.
During my last several months of my service commitment I was approached by NIS (recruited is a good term) to become an agent for them. I asked a simple question "will I have to carry a firearm again"? The answer of course was YES. To which I replied NO. BUT if the agents at that time looked anything like Ziva then perhaps a slightly different answer.
OK back to SDR RADIG's.
Does anyone know the real reason why US military service personnel were called 'doughboys" in WWI. There are many theories advanced such as using white flour to polish their brass buttons (I used Brasso.)
Just a short infusion of information about my military service experience. At my last duty station (Port Hueneme) I had a collateral duty as the Regimental Legal Officer. My assignment frequently required interfacing with the Naval Investigative Service (NIS) now NCIS. Of course NCIS today is a highly popular TV series soon to start season 17. In 1967 there were a lot of issues with drugs including some being smuggled back into this country from South Vietnam.
During my last several months of my service commitment I was approached by NIS (recruited is a good term) to become an agent for them. I asked a simple question "will I have to carry a firearm again"? The answer of course was YES. To which I replied NO. BUT if the agents at that time looked anything like Ziva then perhaps a slightly different answer.
OK back to SDR RADIG's.
It is important to remove your MAGA hat when working on the SDR project as the heat generated from your head and trapped by the cap will impair your reasoning ability. I will remind you when to put it back on your head. Remove the MAGA Cap.
There will be a lot to cover and as a preview of what will be posted throughout the day I want to share some of my thoughts on the hardware build.
NO! Do not light off your soldering iron -- this part of the project is just so you can see what I will be doing with an emphasis on some of the actual hardware like nuts and bolts, connectors etc. I have a well stocked junk box and parts bins --you may not and thusly will need to start collecting non-electronic parts. So I will be making a video to post here sometime today. So check back here several times today.
You are now permitted to return the MAGA cap to your head.
Pete N6QW
June 6th, 2019 ~ Remembering D-Day
I was just shy of three years old on D-Day and remember my Mom telling me this was a great day that would change the world. It did and we should never forget the sacrifices that were made by so many, just so that we can freely tinker with our RADIGS today.
Regrettably our emperor (with a small e) may never understand the greatest generation! OK, time to remove your MAGA hat as there is more to infuse into the brain cells. I will alert you when you can put it back on your head.
One of the most important tasks you should undertake is to organize the information on this project. Set up a directory on your computer entitled SDR RADIG and within that directory create some folders such as "SDR Reference Articles", Part Information, Schematics, Photographs etc. Give this some thought as it will pay big dividends later on as the project nears completion. Dumping everything on your hard drive without any organizational structure is a formula for disaster. Organization is a first on the list.
I will attempt to take many photographs and share them on this blog. Taking that a step further I hope to take photos of all of the setup pages in Quisk so that you can make your Quisk software look just like what I am using.
Firstly you can launch Quisk simply by hit the Raspberry with your mouse and there is a drop down menu. Near the Bottom is a selection that looks like a paper airplane and says "Run". Click on that one and type in quisk and then hit OK. Boom: Quisk will launch just from that one word command. No more calling up the LX Terminal, changing directories and then typing in python quisk.py. You got to love this Linux functionality --works on the Pi or Tinker Board!
Firstly you can launch Quisk simply by hit the Raspberry with your mouse and there is a drop down menu. Near the Bottom is a selection that looks like a paper airplane and says "Run". Click on that one and type in quisk and then hit OK. Boom: Quisk will launch just from that one word command. No more calling up the LX Terminal, changing directories and then typing in python quisk.py. You got to love this Linux functionality --works on the Pi or Tinker Board!
One key item on the Quisk setup is the use of the Pulse ALSA Sound Control Panel* which may be the one item that will prevent your RADIG from working. On the Raspberry drop down menu you can launch the control panel under the Sound Video tab. There is a setting within that control panel in connection with the StarTech 7.1 sound card that by default sets up the input as the microphone -- if you leave it that way your rig will sound dead. That has to be changed to "Line In".
Look back at the Block Diagram the Mic input on the StarTech 71. IS NOT USED!!!! There are various Tabs on the Pulse Audio Control and if you look at the Tab marked input devices and the CM106 Like sound device the Port defaults to microphone --to the right you can hit a down arrow and Line-In is a selection --choose that one.
[*sudo apt-get install pavucontrol is what must be installed using the LX Terminal for installation and the StarTech is identified as a CM106 Like Sound Device]. It is the Sabrent Dongle that is the USB Audio Device Analog Mono.
Look back at the Block Diagram the Mic input on the StarTech 71. IS NOT USED!!!! There are various Tabs on the Pulse Audio Control and if you look at the Tab marked input devices and the CM106 Like sound device the Port defaults to microphone --to the right you can hit a down arrow and Line-In is a selection --choose that one.
[*sudo apt-get install pavucontrol is what must be installed using the LX Terminal for installation and the StarTech is identified as a CM106 Like Sound Device]. It is the Sabrent Dongle that is the USB Audio Device Analog Mono.
If you don't know that you must do that otherwise nothing is heard or it looks like it is working but it is not. Going back to my earlier comment on Organization -- this is where you stash all of the photos so you can match what I have set up to what you must set up.
Interestingly if you hit the last Tab on the Pulse Audio control panel you will see that the Sabrent USB Dongle is Stereo for the Headphones but Analog for the Microphone --all this in an $8 device. Now what is so cool about the Stereo for the headphones is that you can do split operation --and have one frequency in one ear and the other in the other ear -- all this with free software.
While we are at it --many of us are totally new to Linux. Over time I am finding it to be a heck of lot easier to use for this application than Windows 10, especially when doing something more than watching youtube videos on knife making or how to rapid fire your Glock 9MM.
My suggestion for you is to get a RPi3+B and load NOOBS 3.0.1 and make that work. This is a great confidence builder to proceed with the later more complicated actions that come later on when you add Quisk and the other files.
Also time for you to do something more than just follow along. Do some internet and youtube surfing on SDR and save those documents to your computer. This is not just building a kit but a "real learning experience" that in the analog world is like knowing what every resistor or capacitor does. Hwoever SDR operates at a higher stratum in the Systems level. Take a listen to some of the web based SDR and you soon will see -- this is the ticket.
You are now permitted to put the MAGA cap back on your head.
Pete N6QW
June 5th, 2019 ~ More information. Turn off that soldering iron!
If you are wearing a MAGA hat, remove it as it will create a heat zone above your brain and this will cause you to miss some very critical information.
Here is the most critical piece of information (assuming you removed the hat): Essentially we are building TWO direct conversion receivers whose outputs are at audio baseband but out of phase by 90 degrees. It is the further processing of these audio base band quadrature signals that enable the various modes. The further processing of these quadrature signals (like using Fast Fourier Transforms which are loaded into the RPi2/3) also enables the manipulation of the bandwidths. Let that sink in for a minute or longer.
Already many of the readers must be confused since you have looked at the block diagram that was presented earlier and are now looking at this block diagram (created nearly two years ago) and saying they are NOT the same.
But the journey of 1000 miles has a staring point and this is it. The tile is SDR Transceiver Front End and it was just that as this was mated with the Charlie Morris ZL2CTM back end that used the Teensy 3.5 Processor and the Audio Codec Board.
Let us tour this block diagram starting with the relay switched J310's. This has become a standard building block for me and if you have followed my other transceiver projects this is well documented and simulated in LT Spice. So it will be used as is.
The same applies for the Band Pass Filter as to being a standard module and simulated in LT Spice. Don't worry that you have lost that info -- the schematics and part information will be repeated. I didn't say parts list! Part information will be provided. Given our sunspots the initial design will be for 40 Meters. The Ferrite Core Combiner/Splitter will have a modification to include a 100 Ohm resistor across the secondary winding to assure balanced driving signals to/from the ADE-1's, which remain unchanged.
The isolation transformer information was provided in the post of June 4th. But there will be an additional refinement of the hand drawn schematic below (from 11/2017) of the relay switching of the I and Q signals to the StarTech 7.1 sound card. We have the Line In and Line Out (Speaker port) on the StarTech card and we will have two 3.5 mm stereo Audio jacks that will provide the inter connect to the ADE-1 detector board. The Teensy 3.5 and the Audio Codec board are now the StarTech and the Raspberry Pi.
This now leaves the LO which in the 9/2017 drawing was the Si53551 (controlled by ZL2CTM's Teensy 3.5 Code). In order to develop a quadrature (90 degree out of phase) LO signals there is a bit of tricky mathematics. Essentially a single signal is generated at 4 times the final frequency and then fed to a Dual D type Flip Flop (74AC74). There is a frequency division in the flip flopping process that results in two signals that are 1/4 the input frequency (now the operating frequency) and out of phase by 90 degrees. Exactly what we want!
You might be amazed to find out that some of these Dual D Flip Flops can operate to 300 MHz which now means they can be useful operating to 75 MHz --all the way through the 4 Meter band. The 74AC74 will get you through 12 meters.
Yesterday I was asked why can't I just take the Si5351 board out of my Raduino and build your project. Well you could (noticed I didn't say never use that board). But the SDR-Kits board has an ATTiny 45 Microcontroller ahead of the Si570 that comes programmed so that you can interface it directly with other software such as Power SDR, HDSDR and Quisk that specifically have a handshake to the Si-570 AVR USB.
Yet another critical piece is that the ATTiny 45 responds to transmit commands via the USB from the RPi2/3 so that you can TR the RADIG.
So using the Raduino or other Si5351 boards without the several pieces of functionality would be a science project beyond my skill set and I am not sure how you would tune the Raduino with the RADIG. For those with software skills this is in your lane!
So now go back and assure yourself that the two block diagrams are in essence the same with the LO signal being provided by the SDR-kits and the I & Q processing being done with the StarTech and the RPi2/3.
This is a lot to absorb for one blogging session... But we have started the journey. Did you order the free ADE-1's, the free Si-570 and the 5 transformers. You can do that now. BUT again do not plug in the soldering iron and it is now OK to reinstall the MAGA hat on your head.
73's
Pete, N6QW
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June 4th, 2019 ~ Start Here!
SDR for the Masses Part I
His vision many years ago has now forever changed the face of ham radio.. After reading this paper still want to build heterodyne radios or fiddle with drifty analog VFO's?????
STARTING OUR PROJECT:
As suggested by a ham friend in the St Louis area many new to SDR might want to see the seminal paper by Jerry Youngblood (the man behind FLEX Radio.) that appropriately fingers us entitled "SDR for the Masses". (No friend, it has nothing to do with the Catholic Church -- so go back to removing the lint from your MAGA hat.)
SDR for the Masses Part I
His vision many years ago has now forever changed the face of ham radio.. After reading this paper still want to build heterodyne radios or fiddle with drifty analog VFO's?????
STARTING OUR PROJECT:
There are a myriad of ways to start this project; but I thought at the outset it would be well to look at the Quisk Software installation description. This can be found at:
Note there are options to make it work in Windows or Linux. I have not been able to make it work on a small Windows 10 machine but have made it play on a Raspberry Pi2, RPi3 and RPi3B as well as the ASUS Tinker Board. My project approach would be to use the Raspberry PI approach since it does the job and costs only $35. Resurrect that old Pi2 as it will work. But the later Raspberry Pi's have a built in WiFi so you save a USB port.
Why I am suggesting the initial reading of the installation instructions is that it is clear that the software has "built in" the ability to use experimental SDR boards other than some commercial products. This is important as we will not have to undertake a major science project to adapt software. Upfront that is entirely beyond my skill set.
Look carefully at the detail as there will be statements in the guide that will come back to haunt you when your RADIG doesn't work and then it is an email off to N6QW who will say did you RTM? [Read The Manual!]
I already have had a few inquiries about parts and components. Resist buying stuff until I detail what needs to be bought. You can rush off and buy two Triad Modem transformers at $6 each or you can wait until I show you where you can buy 5 suitable Modem Transformers for $4.30 total. These are being supplied from the US and you won't have to await that slow boat from China and pay the Trump Tariffs! [Here is the eBay Item # 401685299674
--these are $4.30 shipped from CA with free shipping!]
--these are $4.30 shipped from CA with free shipping!]
Next take a look at the SDR-Kits website
http://www.SDR-Kits.net
Under the tab marked Kits and Components (a drop down menu) find the QRP2000 USB Synthesizer. There is a 34 page manual. Down load the manual. Noteworthy is that this kit was intended for the softrock V6.2 that used a fixed crystal oscillator and the implementation gave you VFO control. The manual states that it may also be used with experimental boards other than the Softrocks. That is important so this does not turn into a science project as well. I used this same synthesizer with my experimental receiver board last year.
Also significant with this board are two ports for controlling things. One of these ports will be adapted so when you hit the PTT switch on the Quisk panel it will trigger the relay to control the I & Q signals to the ADE-1's. On receive, the ADE-1's will be connected to the Line Input on the StarTech 7.1 whereas, on transmit the Line Out of the StarTech (speaker out) will feed the ADE-1's. This will let you transmit the I & Q where subsequently the signal will be combined in the combiner transformer on out through the Band Pass Filter.
Also significant with this board are two ports for controlling things. One of these ports will be adapted so when you hit the PTT switch on the Quisk panel it will trigger the relay to control the I & Q signals to the ADE-1's. On receive, the ADE-1's will be connected to the Line Input on the StarTech 7.1 whereas, on transmit the Line Out of the StarTech (speaker out) will feed the ADE-1's. This will let you transmit the I & Q where subsequently the signal will be combined in the combiner transformer on out through the Band Pass Filter.
There are many buying options. Get the CMOS version and you can actually get a FREE Si-570 directly from Silicon Labs. Look at the P/N for the Si-570 shown in one of the color photos. You will need that number when you request a sample. I think the exchange rate (or it was about a week ago) is about 1:1, so for about $15 you should be able to get a board in your hands.
I will be building the SDR-Kits board and will use this blog to document my build. If you are somewhat new to soldering small boards you might want to wait for Pete's documentation. Fools rush in and often get the best seats; but at times end up with smoked parts!
While you are at it I was told you can also get FREE samples of the ADE-1 which is the 7 dBm version from Mini-Circuits Labs. You will need two. The ADE-1 has the strangest pricing. If you buy five it will cost you $80. BUT if you buy 20 it will cost $80. Figure that one out. The person pricing those must have graduated from Trump University.
[I have verified you can request up to 4 ADE-1's using the EZ Sample process --just need to fill out some data like what are you going to use them for. Tell them you are following a ham radio project on the Internet to build an SDR Ham Transceiver.]
[I have verified you can request up to 4 ADE-1's using the EZ Sample process --just need to fill out some data like what are you going to use them for. Tell them you are following a ham radio project on the Internet to build an SDR Ham Transceiver.]
So OK lots of homework here. I got an email about this new adventure and the writer said his soldering iron was hot and he was ready to start soldering parts. I told him to take up another hobby! We will spend a lot of time gathering info and getting smart long before we solder the first connection!
73's
Pete N6QW
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In the Summer of 2010 (9 years ago), I penned an article for QRP Quarterly essentially aimed at Newbies that introduced them to SDR. So if any one thinks this is a late in life crisis for me -- well it started a long time ago.
There are two approaches to SDR (probably more than this); but basically we have the use of a sound card where I & Q signals are converted down to an audio baseband and the other more current approach is DDC (Direct Digital Conversion). The DDC has many advantages over the I & Q sound card approach principally -- no sound card and the ability to look at and hear larger chunks of the RF spectrum.
That 2009 article was based on the I & Q sound card approach and so will my current journey. I have as yet to build a DDC RADIG but that will change in time. In my QQ article I state that there are four basic elements to the RADIG. These include the Radio, Sound Card, Computer and the Software.
In 2010 the rig du jour was the Softrock V6.3 with plug in band coils, The Sound Card, typically an M Audio or Erdirol (read very expensive > $100) and the computer could be anything so long at it was > 500 MHz and lastly was the open source software Power SDR (from FLEX Radio) that was modified by several hams. What a thrill to see that waterfall and I was overwhelmed that my 100 MW signal could be spotted via WSPR in Australia some 11000 KM from my QTH.
Fast forward to the Summer of 2019 and the Computer (1.4 GHz), 32 GB SD Card and a suitable Sound Card can be bought for $75 total. The Software for the Computer and handling the SDR chores is a free download (NOOBS 3.0 and Quisk 4.1.39). This leaves the just the radio to be found.
At this point I should mention that there are some stalwart SDR pioneers who have homebrewed an SDR transceiver. One of those is Charlie Morris, ZL2CTM. He used the Teensy 3.5 with an Audio Codec board as the driving force behind his design. For a display he initially used an OLED which easily displayed the spectrum and later moved to an LCD. The software was written in the Arduino IDE thus easily customized with wider or narrower filters (Iowa Hills Software is embedded in his sketch). There are many you tube videos by Charlie and definitely a must to see. I actually built his design and it does work! Should mention that the Teensy 3.5 with the Codec board is slightly more costly than a RPi3B+.
The heart of Charlies rig is a pair of detectors (he used SBL-1's and I used ADE-1's). My implementation used a slightly different front end and because of a noise issue had isolated modem coupling transformers on the I and Q channels. BTW Hans Summers does this in one of his designs. That is where I got the idea.
So OK where does this lead us? My next project is to homebrew an SDR RADIG using the ADE-1 Detector Pair and couple that with LO kit Board (Si-570) from SDR Kits LLC which will provide the quadrature frequency inputs to the detectors. The I & Q in/ out of the detectors will be via the StarTech 7.1 Sound Card and the computer will be the Raspberry Pi3B. The software will be NOOBS 3.0 and Quisk 4.1.39.
About a year ago I had a working SDR receiver prototype that used the SDR Kits LO, the ADE-1's the M Audio Sound Card and Power SDR. It was big and "clunky".
Thus there will be two development areas the first of which is to rebuild the receiver prototype only with the StarTech 7.1 and the Raspberry Pi3B, I recently gave away the SDR Kit LO and an older Softrock V6.2 (the one used in the 2010 article) and so the first order of business is to build the SDR Kit LLC LO and get that working. I will spend some time documenting that so those who are new to building can see how it goes together.
The second area of development is to add the transmit capability. Like in Charlie's rig I will use a relay to switch the Line In and Line Out from the sound card to the Detector board. A notional schematic block diagram is shown below.
Yes, I know it is an "eye chart" but in time it will make more sense. Time to join the SDR gang and move forward.
Caveat Emptor! This is a journey for me as well as I have no 100% certainty that this experiment will work fully in both receive and transmit like some of the SDR kit boards. I do know that the receiver prototype that I built worked very well. But it is a learning journey for all of us who embark on this new adventure.
73's
Pete N6QW
PS: Any one wonder why you haven't seen any recent articles in QQ from N6QW?