Thursday, March 21, 2019

An Arduino Discovery and a Mystery

What should be clear is still veiled!


So OK I have a lot of transceivers that I have collected with most being acquired on the cheap. So while there may be many, the invested dollars are relatively low. Periodically I will drag one out of the storage bin and try to fix the unit. This is done more so as a technical challenge; but often I drive myself nuts in the process.

Here is a recent example. Several years ago I bought a Ten Tec Triton IV Model 544 which is the digital version of the Model 540. Several years ago I actually converted a 540 to a 544 and you can see that on my QRZ page. It was also a subject of an article that appeared in QRP Quarterly. Thus I have a bit of background with this very FB Ten Tec rig.

The Model 544 I have supposedly was hit by lightning and was inoperative. Well that was true; but not a total disaster. (That is why I got it so cheap.) Replacing two back to back diodes that were shorted ahead of the reed relay that disconnects the receiver during transmit cured one of the problems and a new set of finals cured the other major problem. The rig is now operational.

BUT and the Big BUT the display does not stay fixed on frequency. You get that annoying drift of a few hundred cycles and the ever flickering last digit over time. Guys it is still an Analog PTO with a digital readout. That had to get fixed.

Most if not all Ten Tec rigs have an accessory socket where you can add an external VFO and the Model 544 has that functionality. This is where you laugh a bit … on the back panel is an octal tube socket fitted with a jumper plug. [Octal tube sockets and solid state rigs -LOL] 

The stock configuration brings the LO signal to Pin 8 where it is physically connected to pins 6 and 7. The theory is that with these three pins connected, the transmitter and receiver are on the same frequency. With an external VFO connected to pins 6, 7 and 8, then a switching arrangement in the remote VFO enables:



  • Transceiver operation on the remote VFO
  • Transceiver operation on the Model 544
  • Receive on the Model 544 and transmit on the remote VFO
  • Transmit on the Model 544 and receive on the remote VFO
Thus my plan was to essentially uncouple the internal LO which has various ranges depending on the band. The basic PTO operates in the range of 5 to 5.5 MHz and that is used directly on 20 Meters. For the other bands the PTO is mixed with various crystal frequencies to produce LO signals in various ranges from 5 to 19 MHz for injection into receiver and transmitter mixer stages.

I have a band switched Arduino/Si5351 that I simply programmed to match the ranges of the LO for each band. You can even do this with an AD9850 as you only need the LO as you retain the BFO built into the Model 544.

Now you don't even need a display on the Arduino/Si5351. By injecting the proper LO frequency and having the band switch on the Model 544 set to the right band, the internal Model 544 displays the frequencies just like when the PTO was in the loop.

I was joyous as the only modification to the Model 544 was to unsolder the Jumper wire connected to Pin 8 on the external plug. There is no messing with the radio innards.

In fact if you can locate a non-functional 8 pin tube just remove the tube itself and use the base as a new plug. If you go this route then you can do some amazing things like separate the receive and transmit frequencies. My LO sketch includes two VFO's so now you have even greater capabilities.

I made all of the connections (one) and my plan worked. I could tune all of the bands and better yet Ten Tec had an auxiliary band switch to cover the four ranges on 10 Meters. I can do it with just one 10 meter range. 

You do the tuning on the remote VFO but the Model 544 does all of the displaying. What is also nice is that I can manually change the step tuning rate which is nice when you want to QSY across the whole band. The one thing I have not resolved is the offset tuning --not a major issue just something not done as yet.

So I am listening on the various bands and I do happen to have a display on my remote VFO assembly. The Arduino/Color TFT is reading 16200800 and the Model 544 is reading 7.200.8 (with the 8 being a Green LED). Then it happened the last LED on the Model 544 starts to 'flicker up/down" but my Arduino/Color TFT which has a greater resolution is rock solid.

So what conclusions can you draw from this?

  •  Something else aside from the PTO and the Crystal mixing circuit for the various bands is at work.
  •  There is a crystal clock in the internal Model 544 LED display board. It may have some issues and therefore is causing a shift in the time base.
  •  The BFO frequency is summed with the LO in the display circuitry so that the BFO is added or subtracted from the LO depending on the band. The IF is at 9 MHz and thus the LO runs in the 12.5 to 13.0 MHz range for 80 meters. (Subtraction LO-IF.) Whereas the LO runs in the 12.0 to 12.5 MHz Range for 15 Meters (LO + IF). Possibly there are some issues with the circuit that mixes the LO and BFO for the display.
  •  In an earlier Model 544 that I owned there was a problem with the ua723 voltage regulator that had to be replaced and that cured a frequency jumping problem. I did initially replace the 723 regulator as it did have a frequency jumping problem; but that did not resolve the flicker. 
  •  So the concept of a remote VFO is doable with a minimum (and reversible) modification to the Model 544 and this should work for other rigs like the Drake TR-4 or Yaesu FT101 both of which can have remote VFO's. I did something similar to this with an Atlas 210X --so lots of possibilities for updating the older boat anchors.
  • If you want the code send me an email to n6qwham@gmail.com.
  • If you have any ideas about the flickering send me an email to the above address.
  • Pete N6QW 

Saturday, March 9, 2019

So How To Do CW on a Homebrew SSB Rig?

3/16/2019 ~ Remote Antenna Tuning



3/14/2019 ~ Calling All Junk Boxes????


Calling all Junk Boxes, N6QW is looking for a part!

Recently I bought an SBE-33 SSB Transceiver for $52.30 and have been doing some major restorations, which principally involved a great deal of capacitor replacements. I did have to replace the speaker which was blown; but had an exact replacement taken from a Junker unit. 

I have had the rig on the air and so far I am impressed at the 1963 technology --even with an analog VFO. Yesterday running my SB-200 I worked Croatia, 9A5W, Nikola on 40 Meters. That is a big first for me and I got a notable report of how good it sounded. 

A short story --- the dial markings are at every 5 kHz and a ham running a FLEX5000 contacted me to tell me I sounded bad and was not on frequency (7.208 MHz). I asked that he give me some chatter wherein I zero beat him. Then when I transmitted back at him inquired about the signal. He said I don't know what you did but you fixed it. You are now on frequency and the audio is clear. Wow --he has been a ham for 5 years and well I will stop there. 

The Junker SBE-33 has provided many mechanical parts that were missing (the speaker of course and mostly shields although I did have to fabricate one of the shields). Should mention all the transistors are original save for one and I think I have that one too. Look up the specs on a Philco 2N1727 just for fun.   It is now mostly stock and I am down to one item -- The Panel Meter. 

It is blown and I attempted to repair it but can't get it loose from the case. Thus the only option is to find a replacement meter. Not any meter but one that came from an SBE-33. I guess blowing the meter was a problem, as the Junker is minus the meter too.

So if you have an SBE-33 sitting gathering dust in your garage, here is your chance to move it elsewhere. I need just the meter but will take a whole rig. Please advise price and shipping to 91320. I can be reached at n6qwham@gmail.com.

73's
Pete N6QW





3/11/2019

Arduino: How to add the CW capability!

It is always best to turn off the soldering iron first (and to also know which is the "hot" end) and go through a bit of a noodling process to actually think about what you want to do.


  •  Firstly we need to take a look at the Pin Count. If you are using one of the really neat Color TFT displays as I have in many of my rigs you have taken up quite a few of the Arduino Pins. At this point you might want to start looking at an Arduino Mega 2560. Having 54 digital pins will not constrain you on inputs/outputs and the 16 Analog Pins is also a bonus. If you will be using say a 20X4 LCD then the use of the I2C buss frees up a lot of digital pins and opens up the possibilities for using a Pro-mini or a Nano. Overall size of your rig may force a smaller physical size microcontroller. Depending on how much you want to display you might even get by with an 8X2 LCD. When I documented my Bitx40 build which was fabricated just before the Raduino was added, I used an 8X2. You can see that on my website at www.n6qw.com.
  • So from a Pin Count and for the normal SSB operation we have the encoder and step select ( 4 pins including ground). The I2C Buss (4 pins, but two are  5 VDC and Gnd). USB/LSB Select (one pin), VFO A/B Select ( one pin) and TUNE (one pin). True not all are digital pins, as five of those use Analog Pins 1 through 5. So we still have lots of Digital Pins to work with using  the Uno, Nano or Pro-Mini. 
  • Functions we are looking to add to the Arduino: the very first is to have a switch ( 1 pin) that says check if this pin is active and if so go to the CW routine. The very 1st item on the list is to shift the BFO to USB for CW Receive.
  •  Because we are using the Arduino we can accurately generate audio tones and thus we have the option as described earlier of using the tones to do CW. In one of my transceivers when I engage the TUNE function at the end of the pulsed tone I sent my call sign at 988 Hz. It sounded pretty decent. BUT we will have to do a lot of RC filtering as the TONE output is a Square Wave it would be nice to pump a sine wave down the throat of the Balanced Modulator. We will need to designate one pin as the TONE output that we later smooth up.
  • For our CW application there are tones closer to 700 Hz and I will find the appropriate one for the code. By using two pins on the Arduino we can accurately generate timed dits and dahs. By using one of the analog pins (we have three spare ones A0, A6, A7) we could include a speed control so that even though you physically send slower the output can be at a blistering 100 WPM. That will show those SSB only guys!
  • In the code for turning on the Si5351 LO we may need to include a constant, call it c,  in addition to the standard generated frequency and for SSB the constant "c" = 0. But for CW the constant is the amount of the offset. This may not be required but is put on the list so it can be added or not included depending on further noodling.
  • A timed output pin, (only active on CW) would key the PTT and hold the transmitter on for some time period. This output responds to when either the dit or dah key is engaged. Another pin could actually signal different delays --or two pins four delays. 

This is just some initial noodling on my part. But mind you a real Arduino programmer would have all of this as menus where you could select timing levels output speed and delays. But I do think this is a way of adding the capability albeit a bit klunky.
I will have to dust off the QRP Quarterly articles that AI6YR and I wrote to evaluate adding keyboard sending to the mix as that would change some of the functionality I described.
Now the thought occurred to me (and assuming unattended operation is OK for this application) --using canned code and reading the CW, in the morning turn on your rig and all day long the rig is having QSO's while you are at work. How cool is that?

73's
Pete N6QW
          



The Answer is Not a Flippant: Carefully!

[Author's note: A friend in VK4 land made an inquiry about CW operation. I find that 99.99% of my operating time is SSB. But others spend a greater time on the air using CW so why not share some info and data that I have stashed on my computer where a SSB rig can be made to work CW. This also open the possibility of filter switching for a more narrow pass band. With Arduino anything may be  possible.]



My shack is full of homebrew SSB transceivers but only two have CW as an option as well as the normal SSB functions. A design of having both modes must be done with great care and forethought. The rig which does have the best CW functionality is my KWM-4 which hit the airwaves in 2013. 

I spent a great deal of time looking at CW schemes and it became obvious that many commercial rigs included CW as an after thought to aid in the marketing and did not really address the desires and wants of the ardent CW operator.

Here are some of the results of my research. 

  • One method was to simply unbalance the carrier balance control, turn off the mic circuit, crank back  the power and flip a switch often called MOX (manually operated transmit). Thus change over always involved the MOX so no break-in. You essentially keyed the PTT. The offset was poor and involved a lot of leap frogging to copy you. Often there was no side tone oscillator.
  • Another method involved shifting one of the BFO frequencies straight down the throat of the Filter Center Frequency (Cf) and then key a buffer stage somewhere in the loop. This method was OK; but often limited you to sending CW on one side band and receiving on the other. I think the convention now is to receive on USB. Some later commercial rigs let you pick CWL or CWU.
  • Some rigs used a clever approach that employed a tone being generated on "key down" that did three things: 1) the first is you now had a side tone; 2) you now were able to use that tone to key the VOX so you had break-in operation and the third the tone was sent to the microphone input circuit. I think this is covered under Part 97 as tone modulated CW. I think this was the system employed in the Collins KWM-2.
  • For the most part the "value engineering equation" included only one filter often (in early rigs) 2.7 kHz wide. For a CW signal 500 Hz wide that is a lot of signals snaking through the filter pass band.
  • But one homebrew rig in particular from the Dec89/Jan90 QST article authored by the Wizard himself Wes, W7ZOI used a separate crystal oscillator and keyed buffer to generate CW. (The rig was a 20M QRP SSB/CW transceiver.) But even this design had shortcomings in that to do CW you had to hold down the PTT switch. I fixed that problem when I built my version of this rig. This the 2nd rig I have with SSB and CW and predates the KWM-4.

Thus when I built the KWM-4, I looked to address those issues and decided on the W7ZOI approach; but having some refinements.



  • I would use a separate oscillator to generate CW. Somewhere in my travels I found a 455 kHz crystal and this is what I used.
  • My 455 kHz oscillator was turned on for short periods of time but not keyed. A downstream buffer stage was keyed. This is an old-timers technique as this method reduced chirp and key click as you would have in directly keying an oscillator. The short time I spoke of could be accurately set using a timing capacitor. I like a long time between letter so the code sounded distinct. Many CW operators are plain and simple crappy senders using a straight key. 
  • Next the keyed buffer stage was fitted to the circuit so that the CW signal was injected into a bilateral stage ahead of the crystal filter. This was done for two reasons: the first being I could tweak the 455 kHz signal so its offset was more in line with 700 Hz and secondly I did not have to worry about any effects of the filter and downstream circuitry. A small board mounted relay engaged only in CW on transmit disconnected the Mechanical Filter and the preceding bilateral stage fed the 455kHz RF.
  • I then developed a control circuit that did several tasks. One task was to provide break-in operation with a second to have functionality for both tuning the rig with output that required no "key down" or regular CW operation. As a bonus this circuit also providing the switching of voltages to go from Receive to Transmit and even included the usual outboard linear amplifier control. From a block diagram standpoint this is what it looked like.

This is a schematic of how it was done.


I spoke of the relay bypass on the IF Mechanical Filter



Some Snaps of the Control Board





Yes Virginia, all of the boards were made on my CNC machine. I think it turned out pretty cool. But then again I tend to think all that I do borders on genius.

Now with the advent of the Arduino and the Si5351 a lot of what I did six years ago will be just a few pieces of hardware aside from the Arduino. To wit the 1N914's coming off a the 7400 IC could now connected to pins on the Arduino. The timed voltage off of the NE555 is just a Pin Output to a DC switch that is in an "OFF" state until keyed. 

The 4.7 UF was a timing cap. But suppose we use one more pin with a switch that would give you a default time value and engaging the switch selects a different value. Two switches could give you four time values. 

I would consider the use of the third clock on the Si5351 that would provide the CW oscillator frequency that would operate in the same way the standalone did in the KWM-4 and that would feed a keyed buffer.

All of my sketches include a TUNE function that generates a pulsed 988 Hz tone that is fed into the Balanced Modulator. That same code can be modified to provide the timed voltage to the buffer as well as the side tone and show on the display you are in the CW mode. 

I just may have to build what I suggested and then this could be used with other homebrew SSB transceivers. At this stage it is always best to noddle a bit more but I think I have sketched out a possible roadmap to add the Arduino to the mix. If you used a Mega 2560 (more pins) then it would be possible to add my CW sender software so you could add a keyboard for sending CW --and even call up canned messages. With the Arduino anything maybe possible! (For those still subscribing to QRP Quarterly several years ago, Ben, AI6YR and myself did a series of articles on a CW Sender using the keyboard.)

Rock On, Pete!

Pete N6QW

Thursday, March 7, 2019

You Know You Are Gettin Old When ...

Stop Reading this has nothing to do with Ham Radio Stuff!


In a bit of wistful reflection, these days I am taking a more measured approach in what I do.

Take this morning when I was responding to renewing my AARP membership and checked the one year renewal period. I was thinking hey in five years I may not need this --maybe not even three.

Then I thought about what happened in the grocery checkout line yesterday (I was wearing my beret) and the rather attractive lady in front of me had a few items and her total amount was $19.56 wherein I blurted out --that was the year I was in the 9th grade. She turned to me  and said well you don't look that old. (I just know it was the beret).

Then I had a conversation with Go Daddy yesterday about the renewal of my hosting account and the five websites. They were trying to encourage me to sign up for three years. Again my thoughts about who knows if I will still be here in two let alone three years.

That gave cause to my penchant these days to NOT buy a new high technology radio; but instead find the $50 boat anchor specials. In part it is the idea of spending $6K on a FLEX6700 and only get to use it a short time. But maybe buying the old boat anchors is a way to try to relive the past as a way of avoiding the future. 

So if you have similar thoughts --maybe you are getting old too? But we can still learn, still enjoy and still have fun. but we must always think nothing is forever … even the emperor (with a small e).

73's
Pete N6QW

Monday, March 4, 2019

The $52.30 SBE33 Boatanchor

1963 ~ Lots of new SSB Transceivers!

3/5 Late Update ~ On the Air w/SBE33

Well what I posted this morning was a good exercise but it turned up  different problems. The driver (12DQ7) was bad and the reason no indication --- the meter is broken. Upon close examination I saw some very thin wires floating around. One option is to find a company that rebuilds meters. I just set the bias for maximum smoke and we get > 60 watts on tune. Made a contact on 40M with a station in the SF Bay area. Got a good report. We are cooking with gas!


3/5/2019~ Happy Birthday To The US Navy Seabees!

On 5 March 1942 the US Navy Seabees were founded. So to all who "Can Do" hoist a few and Happy Birthday!

In yesterday's post and in the video I mention that I saw no current and no output after fixing the HV supply problem. I guess I was so involved in the many fixes that I didn't take time for a bit of noodling. My brain works while I sleep and so this morning we now have a theory as to the why.

First a graphic and some troubleshooting analysis. In the circuit on the left the Ammeter reads "0" for we do not have a complete circuit. In the right hand side we see the Ammeter (by virtue of Ohms Law) will read "1 Amp". That is the result of 100 volts being impressed on 100 Ohms ---100V/100R = 1 amp






Now that takes us to an analysis of just how is the "Transmit" function activated in the SBE33. There is a very small "ice cube" sized 4DPDT relay that when energized makes the transition from Receive to Transmit. In the receive mode the Cathodes of the driver tube (12DQ7) and the finals (PL-500's) are lifted above ground. Thus no current flows and no output! When the relay is activated then the cathodes are grounded and current flows and output should appear to the antenna. 

Shown below is a partial schematic of how the Three Cathodes in "Receive" are connected through a 270K resistor to the 460 VDC buss; but in Transmit the Relay engages and the Cathodes  go to a pseudo Ground. The Relay may be the issue! I can check this without the high voltage connected as I can simply place an Ohm meter on the Cathode buss and activate the PTT. If it doesn't go to "0" then that will confirm the relay as being the issue. OR that there is an open connection from the cathodes circuit to the relay. Just like the graphic no connection no current, no output!

Note that in the second photo below essentially when that relay is energized it creates a ground point above the chassis ground where the bias supply and negative side of the HV and Screen supply are common to the cathodes of the three tubes. That is why I plan on finding an isolation transformer to prevent me from getting shocked.



Noodling add lots of clarity. I will be checking this out this morning.

73's
Pete, N6QW


****************************************************
March 4, 2019

In February of 1963 Faust Gonsett announced the introduction of the SBE33, which was a hybrid transceiver using mostly solid state devices and three tubes. It covered 4 bands, SSB only and produced a whopping 60 watt PEP. It also used a Collins Mechanical Filter --quite advanced for the time. This would have been a better choice to take to Midway Island versus the NCX-3



Over the years I have had several of these rigs and now added another one to my collection. My winning bid of $52.30 put in my hands. But many of these "bargains" come with a price. Let me explain …


The front panel cosmetics is what caught my eye --really great for something that is 56 years old. So let me explain what I had to do to fix this jewel. I should say I have the receiver working but the final amp stage still has some problems.

The list of issues.


  • First I put the SBE-33 on a variac and slowly brought up the voltages to reform the capacitors. But there was absolutely no sound coming out of the speaker. I put my scope on the audio output transistor and varied the "volume" control. I could see the static pattern but no sound. There is a speaker jack on the back panel and plugged in a speaker --boom sound but no signals. I have a replacement speaker but it is a major disassembly to replace the speaker.
  • I did a crude alignment and finally heard some signals; But there was this terrible popping static noise. I had replaced all of the electrolytic caps so I knew that was not the problem and that caused me to do some noodling. Below is a partial schematic and luckily the transistors are in sockets. So starting way upstream I pulled transistors in the receive chain. Finally I was down to the audio stage where Q1 and Q2 are the audio amplifiers. Q1 is the pre-amp and hung right in the base circuitry is a 0.1 Uf to ground. If that was shorting to ground that would cause the popping noise. I unsoldered one lead and noise went away. I replaced the cap with a 0.1 Uf at 100 Volts


  • I did find the tuning range was down in the CW portion of the band and found that a very small inconspicuous capacitor in the VFO tank network was unsoldered. reconnecting that made the tuning range proper. I also found some rewiring that do not match the schematic and that was corrected. In later production unit every solder joint had a dab of red paint. If the paint was missing then you know that some one had been "diddling" with the wiring. This unit is an early production unit as the decal on the back indicates it was made in Rancho Santa Fe (near San Diego). I can also tell by the fact the fuse is located on a terminal strip on the top side of the chassis. Most later units had the fuse on the bottom side.
  • Next I noted that no matter where I put the USB/LSB switch it receives LSB. My thoughts immediately went to a bad filter. The I looked closely at the filter and noted some really rank connections with bad solder joints. The SBE uses a unique scheme for shifting sidebands. The basic BFO is on 456 kHz. That signal is doubled to 912 kHz and then either doubles or tripled so you get outputs at 1824 and 2736 kHz, (I rounded the numbers). The signal is then injected into a mixing diode following the filter so the signal is added or subtracted to the main IF signal of 456 kHz. Thus the add is 2280 kHz and the subtract is 2280. kHz but with a sideband inversion.  The  VFO operates at 5 MHz and there are injection frequencies of 7, 10 , 16 and 24 Mhz. getting this all to sync is a bit of a challenge. Initially I thought there was a bad mixing diode. --it wasn't. then my attention turned to the filter. Yep the filter was connected wrong! A rewire made the USB LSB correct.
  • There are quite a few alignments and 20M still needs to be touched up but 40 and 80 seem to work OK.
  • I had disconnected the fuse assembly which is in the HV part of the power supply and that brought me to now firing up the HV. After installing a fuse, the good news is the fuse did not blow the bad news no HV. In looking at the schematic following the fuse is a 5 ohm 10 watt resistor. This is so there is some resistance in the mains ahead of the voltage quadrupling circuit. It also acts much like a step start circuit for when you turn on the juice the caps look like a dead short. The resistor looked fine with no burn marks but a ohmmeter across the resistor showed it was open. A replacement 5 Ohm 10W resistor from the junker radio now provides high voltage. 
  • The final amp problem -- no indication of plate current and no output --those are new tubes. So even with a bad driver tube you should see idling current. More super sleuthing work is required
  • It was a bargain price and with much trouble shooting and a few bucks in parts should get this puppy on the air. I hope to check into the vintage sideband net with the SBE33.

If you listened to Podcast #210 I mentioned that an ARC-5 BC453 could be made into a SSB transceiver using the 85 kHz IF. Here is where you can find it:


73's
Pete N6QW

Saturday, March 2, 2019

My First SSB Transceiver ~ 1963.

I was asked a question...


A ham in the Mid-West with a "1" call frequents 40 Meters making contacts and always asks during the QSO "What was your first rig?"

I responded with my 80 Meter ARC-5 and the one tube Tx (6V6). But then I thought about my first SSB rig. It was the summer of 1963 and had just graduated from college and simultaneously entered the US Navy as an Ensign. My temporary duty station in Port Hueneme, CA was a three month school that focused on overseas construction and a dose of how to harden structures to survive a nuclear blast. (It was 1963). 

There was quite an active ham population on the base given that each Seabee Battalion had a complete Collins station that was activated during overseas deployments. KR6SB was the Seabee station on Okinawa. 

I happened to mention to one of the chiefs who ran Special Services that I was headed to Midway Island for a one year tour. He said "you need to take a rig with you and we have a deal with National Radio". So for $200 I had an NCX3 and the matching supply. 

Well I soon found out that you get what you pay for and besides the main ham station on Midway, KM6BI had a Collins KWM-2 and a 30L-1 and a Tri-bander up a 120 foot tower. Guess what I used?

When I got back stateside I sold the National gear and never looked back. That is until last week when I found the NCX-3 and NCXA on eBay. My winning bid was $69. Imagine my surprise that after fixing a loose HV Electrolytic that it works. Then I remembered why I liked the Collins. 

Actually the Cosmetics are astounding and no one has done any "tinkering". There may be a few marginal tubes and some "peaking and tweaking needed" but all in all not a lot needed.

Hers is a video I shot today and even made a contest contact on 20M.

73's
Pete N6QW











Thursday, February 28, 2019

March 1, 2019 ~ A Digitally Controlled Analog VFO

A Digitally Controlled Analog VFO.


So OK here is the great reveal on some of the earlier posts on this blog. I built a prototype of a stepper motor controlling the main tuning capacitor of an analog VFO. 

We now have a digitally controlled Analog VFO. This is the first time that I have actually used an Arduino to control a stepper motor. Old hat undoubtedly to many of you; but a first for me with the Arduino. About 10 years ago I dabbled with a project using a PIC16F84. I was totally lost in the Assembly Language.

We will now, some 10 years later, circle back to that old project. It involved the controlling of a remote antenna tuner. This effort with the controlling of the capacitor with a stepper motor is a stepping stone to the Antenna Tuner.

See my website for more details on the VFO, the code to control the stepper motor including the LCD readout and the code for automatic zeroing of the capacitor on power shutdown. It also describes the Antenna Tuner Project approach and how the LCD will provide the readout for setting the capacitors and the tap points for the inductor using shorting relays.

http://www.n6qw.com/StepperMotorTesting_PartII.html

Be sure to visit Yvan's website www.brainy-bits.com for the many excellent  tutorials. It all started with his you tube video.

But for now as you will see the whole thrust of digitally controlled Analog VFO was to give deference to my friend Bill in recognizing the relevance of the analog VFO in today's rigs. At the same time we have the ability to add a touch of "digi" stuff to simulate the HRO dial mechanism.

73's
Pete N6QW


Wednesday, February 27, 2019

2019 ~ Big DX Contest Coming Up this Weekend

Big DX Contest This Weekend!


In preparation for the contest I reconfigured one of my 40 Meter rigs so it will work on 20 Meters. It was a pretty simple change over. Unsolder two caps in the BPF and retune the Trimmers and then swap in a pre-made 20M LPF. 


This is the two Filter, two VFO rig with a wooden front panel and of course the cool 20X4 display.

There are quite a few stations in the Caribbean that were testing their stations today. I picked a PJ2, and an HR8 using this rig with an outboard amp at 80 watts. I had my beam in line but can tell it is at times intermittent. I think it is a coax/connector problem at the beam itself. On the list to get fixed ASAP.

What I didn't mention was three lines of code changes, 5 minutes on the computer and I reset the tuning range to 20 Meters. Kind of hard to do with  analog systems unless you have a bunch of heterodyne crystals. 

VFO B defaults to FT8 on startup -- need to test FT8 on 20 Meters. Tomorrow.

The Red knob on the lower right hand side is the TUNE button. When the MOX switch is flipped on and the button momentarily pushed the word TUNE appears on the LCD right after the word Rig. After the 7 second cycle the word disappears and the rig returned to normal operation. During the TUNE a 988 Hz tone is generated and then pumped into the microphone circuit (following some filtering and attenuation). 

73's
Pete N6QW

An Arduino Discovery and a Mystery

What should be clear is still veiled! So OK I have a lot of transceivers that I have collected with most being acquired on the cheap. S...