Saturday, July 20, 2019

RADIG ~ Ham Radio's new Tsunami Wave Issue 16

NOOBS 3.2 Image Success (some issues remain)!

I went back and retried the Raspian Image process. Firstly I deleted any thing NOOBS Image on my Windows 10 machine and emptied the wastebasket. A new download, move to the Zip directory, extract to that directory using their recommended UnZip program and then with my disk imaging software loaded up the SD Cards (yes two of them so it worked twice).

Into the RPi3 with both cards and all loaded OK. Next was to install the latest QUISK 4.1.41. Got two cards now with the NOOBS 3.2 and the latest QUISK. 

Noteworthy the 2nd Card is an 8 GB and you just about fully load that card with NOOBS 3.2 and QUISK. So yes, you can do it on an 8 GB SD Card --but not much room for anything else.

Here are the issues remaining. When you make changes to the configuration there is a "restart quisk" button that normally will restart QUISK and you get the program back. That doesn't happen and the changes don't get made. So my work around is to make the changes and close out QUISK and then launch it a second time. This usually results in the new configuration. 

Using the RUN tab does not always launch QUISK and you at times must resort to the other method where you use the LX Terminal to change directories to the quisk directory and then type in python That usually always launches the program. I also note when you can get the RUN method to work --your beard grows while you await the program to launch. It is really slow as compared to NOOBS 3.0.1

There must be some software bugs remaining in the new NOOBS 3.2. That was not the case with NOOB 3.0.1. 

Or what has been suggested by a blog reader. The new NOOBS 3.2 is running on Python 3.0. QUISK is designed to work on Python 2.7. On January 1, 2020 Python 2.7 will have EOL or I think they call it deprecated which rhymes with eliminated. [Sounds like what used to happen in my home town in western Pennsylvania --there were often eliminations of rival organized crime members.] The QUISK Designer has stated he is working on a Python 3.0 friendly version of QUISK but Python 3.0 is not in the current QUISK. 

The blog reader also advised that even though you might have loaded Python 2.7 -- both versions maybe on the RPi3 and I guess there is some sort of hierarchy determination where the latest version is used. I have been advised to initiate the following in a LX Terminal python  This should now return which version is being used. If it comes back 3.0 then the mystery has been solved. I will post the results: The return is Python 2.7.16. Not the issue with the Python version although the caveat about Python 3.0 still looms large about 6 months from now.

My parts for Prototype #2 which I was assured via the tracking app would arrive by 8:00 PM yesterday must be in the stealth mode. No Parts arrived at my door step. They were shipped from a location 20 miles from my home and we are now in the 4th day!

Pete N6QW

Friday, July 19, 2019

RADIG ~ Ham Radio's new Tsunami Wave Issue 15

A Wish List of RADIG Modifications!

Well no parts in the mail yesterday for Prototype #2 so I am stuck writing dribble for this blog! But I did think I would share some of my "wish list modifications". For those of you whose strong suit is software and Linux --this is your chance to be heard. Use my email contact address.

Some of my wish list items are hardware only (easier for me to do),  while others (more extensive) are hardware driven by software and this is the nut to be cracked.

Hardware only Wish List

  1. First on the list is power connections and power supplies. Typically the power supply for the Raspberry Pi and the ASUS Tinker Board is a Wal-Wart. Because of more things and actually bigger processors / more RAM, the original RPi supply requirements have crept up from say 1.5 amps to now the suggestion of a 3 amp supply. The RPi4 even has shifted to a USB C power connector. In one of my RADIG configurations I have two 2.5 amp Wal-Warts --one for the RPi3 and the second for the backlight on the 7" HDMI screen. Thus you would need to supply 5 amps at 5 VDC, although I don't think the HDMI needs the full 2.5 amps. I have thoughts of putting the RADIG in a box, which begs the question of how do you handle the Wal-Warts. The second part of that is portability and suppose you wanted to take your RADIG into the field or possibly to a park bench as a lure to attract YL's. 
  2. Thus I am looking into designing and fabricating a better power supply system. The first piece of that design is to locate some Micro USB cables that are designed to carry power --they are available --just need to find a P/N and supplier. 
  3. There is a branch design approach here. One branch would simply cut off the other end of the standard 4 pin USB type that is at the other end of the Micro USB cable, wherein you route it to a terminal strip. There would possibly be two uses for 5 VDC and subsequently terminate the source strip at a bulkhead power connector. Then using say a 5 VDC, 5 amp DC power supply as a source, it would just plug into the bulk head connector and "Bob's Your Uncle". This is a designer's dilemma --there are many "box top extra's" who would never read the directions and would simply plug in 12 VDC to the bulkhead connector and boom -- you blow the HDMI and the Raspberry Pi. That my friends would be a costly $100+ mistake. So you need to think about the second branch. This first branch also has portability issues.
  4. In this second branch we use a bit of technology that is readily available and this circumvents the "box top extra" non-techie types who never read instructions. It is called a DC to DC converter. At the bulkhead we have one 12V DC (or 13.8V DC)  input power connector capable of handling about 6 amps --yes 6 amps. The two pin Jones Plug would be ideal. Then from the chassis side of the power plug you can wire a panel switch on your enclosure so you can power ON  or power OFF the main supply. Next the 12V DC is routed to a terminal strip where you can connect the main supply to the RADIG main board and the RF stages. Another connection (technology here) is the DC to DC converter. Mean Well makes a 9 to 18V DC input converter with a 5V DC output at 5 amps. Let this sink in --about $20 for this jewel. I have used this converter technique before when I needed to operate a 24V DC device off of 12 DC. Mean Well makes that converter too. Now here is the bonus --batteries --you could operate the RADIG on a park bench even when the battery supply might be below 12V DC--it will still operate the converter. Jameco Electronics sells these converters under P/N 175662. Thus my power supply thoughts takes us to a single supply to the RADIG of 12V DC (13.8V DC) to operate the RPi3, the HDMI and the RF electronics. If you think you might add a bit more hardware you can up size the DC to DC to 10 amps (same 9 to 18 VDC in) for another $5. P/N 212549. We no longer need to fear the "box top extra" because I also have included a 10 amp relay inside the enclosure that will only energize with the correct polarity of the supplied source. We fixed the 12V DC into 5V DC but we also have to be concerned the BTE's will wire the power plug incorrectly. 
  5. Next item: Cooling --heat is an issue --5V DC at 3 amps can get hot and even though the RPi3 has a heat sink when used in a warm environment like my 85 degree garage shack --you start seeing a thermometer on the screen. So fan cooling is a must --especially if you put it in an enclosure. In one case I modified the plastic RPi case to add a 12V DC very small cooling fan on the top to suck out warm air and the thermometer on the screen does not show up with this arrangement. But if we add the Sound Card Hat that presents some problems with placing a fan over the top of the board. So I am researching some small 12V DC fans that would be physically located near the edge of the RPi board and blow across (as opposed to above) the processor. I also note that the heat sinks on the ASUS Tinker Board are physically larger than what I am using for the RPi. So a quest for bigger heat sinks is also in order. OK --why hasn't any one said Pelitier Junction on top of the RPi --worth a look as well. 
  6. Compact size is not on my list but perhaps on yours. I happen to have a 12X10X3 NIB aluminum (as opposed to our UK friends who say and write aluminium) chassis that I will be using for the Prototype #2. This size looks to be ideal so I can mount the 7 Inch HDMI Screen on that chassis as well as supply space for controls, audio headset/microphone jacks and an external speaker jack as well as some status LED's. Maybe even a Tuning Knob --- read on.
Software (with added Hardware) Wish List

This is where my sense of frustration looms large and I reflect back to the early Arduino days where I couldn't get the LCD to say Hello World. But I don't think I have enough years left to feel comfortable with Linux or Python. Darn once again too little knowledge too late in life. 

I know what I want to do can be done as I have done these very same things with the Arduino; but can only have a blank stare at the RPi3. There is that 40 Pin Header looking very naked with nothing connected to it and what is worse I know connections can be made to it; but there has to be some instructions behind those connections. So OK you software weenies time to stand up and be counted.

  1. First on the list is a Tuning Knob. I have seen code where you can bring out interrupts to the 40 Pin header and you would need three of them. Two would operate an uptown optical encoder and the third would be to set the step tuning size. Behind the encoder there would need to be an interrupt service routine (ISR) and QUISK code modification to respond to the encoder so it up down tunes the frequency. Currently you change frequency on QUISK by either keyboard entry or by moving the mouse on the screen. You would want to keep these but also add the Tuning Knob. I sit here knowing what I want, can visualize some of the things that would need to be considered but simply do not know the "how" part.
  2. Second on the list is band changing. Right now to change bands you simply click a tab on the control panel and I believe you can also enter the new band frequency on the keyboard --haven't tried that. My Omnia responds to the band change via the control panel button and somehow magically the right filters are put in place and there is no tie in to the GPIO. However with other radios I physically have to change Band Pass and Low Pass Filters. How cool would it to be if we could use the GPIO pins to "ON" filter relay banks to change bands in concert with the control, panel selection. I have done this with Arduino using a band switch to change the frequency range on the Si5351 and at the same time select the right filters for that band. So why not have Pins on the GPIO have 5 VDC appear in concert with the band change on the QUISK control panel. Just don't know how to do that.
  3. Our cooling fan --how about a temperature sensor on the RPi that would sense when it is getting too hot and then the fan gets turned on or runs at a different speed. I can tell you that the fan I installed on the RPi case runs all out, all of the time --and even for me is annoying. 
  4. An Analog or Separate OLED Display of the S Meter. There is an S Meter on the control Panel -- but really small.
  5. Since the RPi3 can talk to Arduino -- maybe some of this stuff I am wishing for can be done in Arduino where I have a ghost of chance of hacking through with it. But the Pi was designed so you can get access through the 40 Pin GPIO Header -- I just don't know how to modify QUISK for some of these wishes while others I could do with an Arduino and link those although not seamlessly to the RPi3.

So email me at the email with your solutions.

Pete N6QW

Thursday, July 18, 2019

RADIG ~ Ham Radio's new Tsunami Wave Issue 14

New RPi4 Software and Yet Another New Sound Card for the RADIG.

[Quick Synopsis: (1) The new RPi4 software has problems with QUISK. (2) A new Sound Card Hat for the RPi3]

The Raspberry Pi Foundation recently released the RPi4 under the banner Faster, Better, Cheaper. So far there seems to be high marks for this new board and indeed there is a variant that can be had for $35 Bucks --a benchmark for them!

There are some caveats as you must (MUST) use the latest NOOBS software with the RPi4 but supposedly NOOBS 3.2.0 (the new OS) is backward compatible with the RPI3 (and maybe even the RPi2) Having some time as I await some hardware parts for the Prototype #2, yesterday, I wandered over to the RPi official website, and looked up the new software. 

There I found that you could download the latest NOOBS and the image of  Raspian. Now I am going to tell you a lot more than I really know or understand. The NOOBS software can be downloaded as a Zip file, then extracted and loaded onto an SD card. Once installed into a RPi there is an agonizing process where the files get extracted onto the Pi and then installed. The image approach (which requires disk imaging software) is unzipped and then loaded onto the SD card and when you plug it into the RPi --it is ready to go. I should add that the OS for the ASUS Tinker Board is done this way.

With the image it is a lot less time consuming as I will share in a moment. I found that to be super easy to do with the Tinker Board where after boot up and installing about 15 files just to do QUSK and I was on the air. If you go to my website one of the links talks about the software installation process. 

Thus I downloaded the new NOOBS and the Raspian Zip Files which are separate links. Now here is the interesting part -- neither will be easily unzipped using the run of the mill unzip software that typically comes with your computer. The download info on Raspian (not NOOBS) tells you that and also warns that often files get corrupted using the Raspian image. The NOOBS 3.2 link does not mention the special Unzip software.

Well I downloaded both zip files and sure enough, my one year old Windows 10 computer would not unzip the files. So back to the RPi website to get the special unzip software. Even then you had to perform an arcane process to make it work

  • Step one install the Unzip Software to your computer and then install  a directory on your C Drive called Zip files.
  • After downloading the two Zip Files cut and paste (without trying to open them) them into the new directory you just installed. Launch the new Unzip software and navigate to the Zip file directory and perform the extraction process. It works! BUT a curios and  bad sign -the Raspian files (image) while extracting shows two errors. The NOOBS 3.2 sailed through without error. 
  • I tried loading the Raspian image on to an SD Card and then installed it in an RPi3 -- it got half way through the boot up and hiccupped --bad file and not synching. So much for the RPi Raspian image and new unzip software
  • The NOOBS 3.2 took a very long time to install. NOOBS 3.0.1 ends up with about 4GB of installation -- whereas the NOOBS 3.2 is over 5 GB. It took over 30 Minutes just to load the basic RPi software and then another 20 minutes for QUISK.
  • Once installed there were many of error messages and lots of hiccups; but I did manage to get it to work. What I had to do is uninstall (remove) some of the sound related files and then reinstall them. This is reminiscent of Arduino new IDE's that wouldn't work with older LCD libraries. It is working now; but I still occasionally get error messages. This is not Faster Better Cheaper for this application with an RPi3. I will see if I can load NOOBS 3.0.1 onto my website so you can download it from there.
  •  The website now has the NOOBS 3.0.1 Zip File Link -- it is a large download file but you now have a version of NOOBS that works with QUISK 4.1.41. Kind of cool just learned how to put Zip Files on my website --so a good exercise.

For you software weenies --look what you do to us hardware guys -- it was nearly a whole day of screwing around with software only to have day old bread! Now if you are using an RPi4 (which I do not intend to purchase) things might go better. 

Backward compatible is like explaining the terrific gas mileage on a Maserati -- if you go only down hill with no gas applied --it will do 20 MPG. What that is saying is NOOBS will work with an RPI3 but if you want it to really work all of the time possibly you need the RPI4. I was also using the latest QUISK 4.1.41 and am not sure if any one else has tested QUISK with the RPi4 software. Caveat Emptor!

New Sound Card Hat for the RPi

Dave, WB6DHW,  put me on to this new "hat" for the RPi. Essentially a hat is a device intended to plug into the  40 Pin GPIO header on the Raspberry Pi (and I suppose other SBC's that have compatible 40 Pin headers like the Tinker Board) so that no other wiring is needed for operation and it releases a USB port for other uses. 

Well here is a sound card hat shown below. It not only has a built in CODEC but ports for Line In and Line Out as well as a combo port for Headphone and Microphone. This has the potential for eliminating two sound cards with the RADIG. The board alone is about $12 and the header is ordered separately as is the Video connector (not sure what that does).  You can easily see the Line In Line Out and the headphone / mic. You will need one of those funny (4 contact)  two ring, sleeve and tip connectors for accessing the mono mic, stereo headphone jack. All Electronics sells them --about $2. The Company FE-Pi in Arizona will have stock in next week.

I will be ordering one -- so wait until I get it installed and tested before leaping to buy one -- but this could really shrink the size of the RADIG. I am very hopeful. For those who parse everything and anything (AKA EMRFD Illuminati) the  CODEC is a SGTL5000.

Now for those of you with mechanical engineering skill sets -- the obvious question --Thermodynamics. The RPi generates a lot of heat even with a heatsink, when it is cranking away doing all of those FFT calculations. Even a heat sink is not enough. There is so much heat generated when mixed with a warm environment of my garage shack,  I have even added fan cooling to the Tinker Board. This hat when installed sits right over the heatsink --so some form of auxiliary cooling will have to be fitted to the board. 

A friend W6KAN (Tom) who has built a lot of LDMOS amps has resorted to having the copper spreaders on his amps fitted with copper tubing and runs cooling water through his heat sinks. Taking an idea from W6KAN will I have the very first water cooled Raspberry Pi? Small is good but also causes some unintended consequences.

Pete, N6QW

Wednesday, July 17, 2019

RADIG ~ Ham Radio's new Tsunami Wave Issue 13

A Question and an Answer.

My age is showing and I guess I am now at the real grumpy age. My following comments reflect a question and answer I provided in regard to the RADIG QSO shown here.

The question from the video was: What SDR Type. It was not even a question as it had three !!! following the statement. So one person other than myself (overnight) tried to respond by saying it was home made. The original poster of the question seemed annoyed by that answer and spouted off a bunch of kit boards (by name) and wanted to know which one.

We are basically amateur radio operators! Some of us non-appliance operators delight in expanding our horizons by experimenting using new technologies. Some times we get lucky and there is a convergence of the star alignments and what results is a RADIG!

Well (here is the grumpy part) I was now annoyed by that question and reading between the lines more importantly the attitude of that person. He was "demanding" to know what was the board. Here was my response.

Thanks for your question. But the answer is in several parts as you were not definitive by what you meant by What SDR type!!! Clear to you maybe but not to others.

First the RADIG is not a kit nor is it a board you can simply purchase. It is a transceiver "homebrewed" by me based on some earlier work by ZL2CTM, Charlie Morris. I essentially started from scratch!

Starting with the basics there are at least two variants of SDR Types --there is the Sound Card (I & Q) which this is, or the DDC which uses no sound card.

So there is a sound card to take signals that are converted to audio baseband via my home made convertor and processes those signals and decodes those signals and displays them  on a screen.

The Sound Card is a StarTech 7.1

For a computer you can use either a Raspberry Pi3 or an ASUS Tinker Board (Linux)

Foe the SDR Software I use QUISK developed by N2ADR

For the audio output and Mic input I use a Sabrent USB Sound Card Dongle that plugs into the Pi3 or Tinker Board

The home made convertor board is bi-directional (used both for receiving and transmitting). It consists of  two ADE-1 Double Balanced Mixers (you can also use SBL-1's) and using two Local Oscillator signals at the same frequency but in quadrature (90 degrees out of phase), the incoming signal is split into I and Q channels at audio. In essence you have two direct conversion receivers.

There is a hybrid coupler transformer ahead of the ADE-1's that splits the incoming received signal into two separate signal paths but also functions on transmit to combine the I and Q channels into a single outgoing signal. The Local Oscillator is at 4X the operating frequency supplied by a USB Synthesizer board from SDR-Kits LLC in the UK. It uses an Si-570. and the signal from the USB Synthesizer board is divided by 4 and spit out in quadrature using a simple 74AC74 dual D Flip Flop. This IC is good up through 12 Meters

There are some other pieces such as the 3 section Band Pass Filter and a pair of J310's configured as a Dual Gate MOSFET that is relay steered so on receive it is the Rx RF amp and on Transmit it is the transmit pre-driver. For a driver stage I use a 2N2219A and the final RF amp is an IRF510. For the transmit Low Pass Filter I use the W3NQN design. The power out is about 6 watts. But in the video I had two outboard linear amps that produce in excess of 600 watts to the antenna.

So what you see in the video is all of the above working as a transceiver. I have a website that details much of what I have written.

If you are looking for a simple kit board answer (I think you hinted at that in another posting you made) there is no kit board. Basically we have a down/up convertor to/from audio baseband using a Raspberry Pi3 or ASUS Tinker Board Running the QUISK Software to provide the basis of an SDR transceiver

This is ham radio from the old, school -- you think about what you have to do and then find the pieces to make it happen. This is not an appliance --it is true ham radio --built from the ground up.

Pete, N6QW *******************************************************************

Monday, July 15, 2019

RADIG ~ Ham Radio's new Tsunami Wave Issue 12

Some Input and Some Data

[The following was in a fortune cookie served up at lunch today at our favorite Chinese restaurant: 

The human spirit is stronger  than anything that can happen to it. 

Words of wisdom for us to ponder regarding the deep meaning this conveys.]

Firstly, I should mention that I have had quite a few more contacts on the RADIG and the results have been very positive. So I think this could be on track to becoming a frozen design. 

A few comments received include when are you going to make it look "pretty" and put it in a box? Frankly cosmetics are not high on the list; but I do agree having it in a box would make it better for show and tell. Thus I am building a 2nd prototype and that will be in a box and the 7 Inch HDMI will be affixed (somehow) to that box.

I also received a comment about demonstrating the RADIG in an actual on the air QSO. I agree and will endeavor to do so in the next day or so. All I need is the Radio Gods to cooperate and have the bands improve. I will post the video as public on you tube and on this blog. Here you are...

I have received a nice email from Dave WB6DHW click on the link for boards and kits. Dave was sharing with me that for over ten years he has been commercially producing an SDR kit that works well into the UHF range -- try 700 MHz. He uses an IC that divides by two (versus 4 as with the 74AC74) and is capable of operating at 700 MHz. He also uses a variant (not CMOS) of the Si570 that works well at 1.4 GHz, His RF and LO Signals feed an ADE-2 which can handle the divide by 2 at 700 MHz. As Dave pointed out his approach and what I have done with the RADIG are similar in nature (not design)  but my RADIG is sort of limited to HF because of the components and methodology used. I can see the UHFSDR (Dave's product) working nicely on 6 and 2 meters with SSB and FM

His SDR board is small and looks like it would almost fit in an Altoids tin. The UHFSDR  is well respected in the SDR community and as was indicated  by Dave has been around for well over 10 years. 

I do not know at this time if QUISK will work with Dave's board. I do suspect that if you can software set the frequency divider to divide by two versus 4 --then it should work FB. Once the LO is supplied and you have the I and Q --then QUISK would probably not care. Dave has a whole array of kit boards including the mainboard and the Si570 board and Microcontroller and many other kit boards including Low Pass Filter boards used on other commercial amplifier kits that lack such boards. Check out his website.

I have  a UHFSDR board that goes back about 8 years that I got in a buy of some SDR hardware from another ham, I think the output was about 10 MW so you have to add some afterburners. Unfortunately the board I got (literally free) was in op -- guess that is why it was free. I am not sure about the power output on the current board production. But the 2N2219A stage could take that 10MW and boost it to something you could use to drive a IRF510.

Visit Dave's website -- and drool like I am doing.

This will sort of wrap up the RADIG for a bit as I concentrate on building the 2nd prototype and add some of the new circuits such as a band switched Band Pass Filter Module and the new J310 stage. So if it seems like a black hole for a while it will be just that. 

This is a cautionary note. Building and making the RADIG work very likely is not for a first time builder. So if you want to enjoy having SDR on a budget -- get Dave's UHFSDR kit where you might have to use Power SDR or HDSDR for the software in the event QUISK is not adaptable or Tony Park's Ensemble Kit at Five Dash that works directly with QUISK. '

Pete N6QW 

Sunday, July 14, 2019

RADIG ~ Ham Radio's new Tsunami Wave Issue 11

The J310 Amp & WSPR

One test I like to run with my transceiver projects is to let them operate on WSPR. This test, that typically will run several hours, enables you to ascertain how well the rig hears and how well is it being heard. This same series of tests is also a good way to test your antenna. Recently I upgraded my "droopy dipole" to one where the center height was raised from about 23 feet to nearly 35 feet and this was the first WSPR test with the revised antenna.

This is data taken over a three a hour period starting at about 6 PM last night and the RADIG was running a puny 5 watts (who runs QRP?). I was heard in Antarctica about 14000 KM from my QTH in SoCal. I think that also may be the 1st time I was heard in Brazil. You can see the band was very active. I even took a bit of a trip to FT8 land and worked a station in Cuba. 

But I must confess while on FT8, I was not running 5 watts nor 600 watts. So this just gives you a one slice snapshot that the RADIG indeed works on the digital modes. Keep in mind all done with a Raspberry Pi3 -- the built in WiFi makes for easy and automatic uploading of the WSPR spots.

The J310 Amp Stage!

OK now to the J310 amp. If you haven't guessed by now I have a lot of modular boards that are simply moved around from old projects to new projects. Often the designs using LT Spice may be optimized for a specific band but also you can stretch the boundaries and say --that would probably work on a higher band (I didn't say work as well but just that it would work). 

That is the exact situation we have with the J310 amp in the RADIG as it was previously designed for primary use on 40M but looked like it would cruise over to 20M. Here is a schematic and plot of the output from that amp which was first designed several projects ago.

Note it says Broad Band (not Ina Ray Hutton's Band) 40/20 Meter RF amp.

You need your Squinty Eye Glasses to read the plot but essentially there is a 3 dB drop from 7 to 14 mHz. So does it amplify at 14 MHz? Yes, but the received signals are about 1/2 power less than (ok guys in the old days 3 dB down was known as the half power point) signals at 7 MHz. You can run a math exercise to prove to yourself that as you double the power it is a + 3dB gain. Or you can learn how to use LT Spice and run the circuit yourself.

So how do you fix this? Well one fix is to make the circuit have greater bandwidth (that can be done) but there is another old school term not often used these days. It is called gain bandwidth product. The broad band linear amp stages that often follow appliance boxes have a sorta flat gain over a 30 MHz range which we often take for granted. There are specific circuits in the designs which cause this to happen; BUT is often less power output than a narrow band amplifier over a smaller frequency range. 

That BB 100 watt amp will do 100 watts over 30 Megahertz. But if you designed it for a narrow range of frequencies you might see 140+ watts for just that narrow range. Circle back to gain bandwidth product --meaning the gain times the bandwidth is more or less a constant. Smaller bandwidth = higher gain over that bandwidth or lesser gain but greater bandwidth over a larger range. That is often a designer's dilemma. Now that was very clever to call it gain bandwidth PRODUCT --- meaning the gain times the bandwidth = a fairly constant number.

So when I took another look at the J310 amp I chose to make it a flatter bandwidth to cover 40 through 15 meters thereby opening the frequency range where you would have flatter gain, with a reasonable (but lesser) gain than a narrow band amplifier across a larger frequency spread. This design output plot is presented below:

Now the gain has been shifted to be > 1 dB at 14 Mhz versus that at 7 MHz. The gain bandwidth will now favor the 30,20,17 and 15 meter bands. So for those who want the higher bands seeing as we will be heading out of the sunspot cellar this revised amp is just the ticket. When you look at the plot in detail there is only less than 1/2 dB gain drop from the peak value to 20M and still significant gain (over the prior design) on 17 and 15 Meters. 

So what has changed? For one the biasing resistors and the feedback in the Source as well as removing the 2.2K resistor fromerly on the Gate to ground connection. Additionally some capacitor values were changed.

There you go --have at it. In the final analysis the Gain has been flattened for the higher frequencies while reduced somewhat for 40 Meters. But given that 40 Meters already will have many strong signals the increased gain at the higher frequencies will make the RADIG hotter on bands above 40M, which was one of the early concerns stated in an earlier posting.

Are you keeping up?

Pete N6QW

Saturday, July 13, 2019

RADIG ~ Ham Radio's new Tsunami Wave Issue 10

Some New Data ~ Data Points

Here is some setup and reference data for the RADIG. Today I looked at both the design of the J310 Amp stage and the drive levels from the Si570 on all bands. 

Starting first with the drive levels. I put a scope on the output from the pot as it connects to the LO Port on the  ADE-1 and the results are a bit surprising. Keep in mind that the actual frequency being generated is 4X the operating frequency. So at 10 Meters the RF from the Si570 is around 120 MHz. 

  • 160M ~ 544 MV PTP
  • 80M ~ 544 MV PTP
  • 60M ~ 544 MV PTP
  • 40M ~ 544 MV PTP
  • 30M ~ 544 MV PTP
  • 20M ~ 544 MV PTP
  • 17M ~ 512 MV PTP
  • 15M ~ 472 MV PTP
  • 12M ~ 377 MV PTP
  • 10M ~ 320 MV PTP
The outputs below 15 Meters were nice square waves and the surprise was that the lack of sensitivity would most likely only occur on 12 and 10 Meters. Thus my observation of lack of sensitivity previously on 20 Meters was more likely driven by the J310 Amp stage and not the LO drive level.

[This is where the EMRFD illuminati  are supposed to jump in a decry the results. Actually you must look a little more closely at the 12 and 10 Meter numbers as there may be other factors that are skewing the data. There are variants of the 74AC74 that are good to 300 MHz; but this old plain garden variety is only good to 95 MHz which of course is a bit below the 4X for 12 and 10 Meters. So I think what I am saying is that the Si570 is not the bad apple in the barrel. But the lesser drive (resulting from the 74AC74) would impact 12 and 10 Meter sensitivity.]

Back to the J310 stage. Sure enough when I went back and looked at the simulation-- there was about 3 to 4 dB less gain at 14 MHz than 7 MHz. I will now look at a redesign of the J310 amp stage. It may involve just three components. Once I get it potted I will share it on the blog. 

More contacts with the RADIG including a 40M coast to coast with the RADIG and 600 watt amp last night. I got a very nice report. [ At 1630 left coast time today I worked the same east coast station -- that is early for the path. But once again a great signal report. The RADIG Rocks!]

Pete N6QW

RADIG ~ Ham Radio's new Tsunami Wave Issue 16

NOOBS 3.2 Image Success (some issues remain)! I went back and retried the Raspian Image process. Firstly I deleted any thing NOOBS Imag...