Category: SSB

Video: Introduction to the TinySA Spectrum Analyzer

The TinySA has some very cool capabilities, and this short intro video provides a good sense of what it can do.

I am learning how to use the TinySA so that I can check the output of my Mythbuster transceiver (I now have the first portion of the transmitter working.) I tried to use the TinySA to check the carrier and opposite sideband suppression on my new Mythbuster transceiver, but I think the max Resolution Bandwidth (3 kHz) is too high for me to do this. Please let me know if I am missing something. That would have been a very useful capability.

The rest of the videos are here:

It also functions as a signal generator that also provides AM and FM modulated signals. You can also have a waterfall on the spectrum display. Very nice.
I have not yet figured out how to listen to the signals. This is one of Erik’s videos — it looks like you have to solder in a connection for audio out.
Thank you Erik Kaashoek.

QST Recognized Error on Sideband Inversion, But Continued to Make the Same Mistake

I don’t really know if this is good news or bad news. It’s good that in November 1985 they recognized the error, but then they allowed the same error to be repeated by the same author in the 1989 article “A Four-Stage 75-Meter SSB Superhet,” and again in 1990 in W1FB’s Design Notebook. It also made it into the 2002 ARRL Handbook.

Thanks to Chuck WB9KZY for alerting us to this Feedback piece.

QST Repeatedly Got Sideband Inversion Wrong

It kind of pains me to do this. These articles are from a long time ago, and the author is an esteemed Silent Key, but the myth about the origins of the USB/LSB convention is still out there, and as a homebrewer of SSB gear I feel obligated to point out these examples of the error that that myth is based on.

Last Friday, Pete WB9FLW and I were talking about homebrewing SSB rigs. I recommended a series of QST articles by Doug DeMaw. “Beginner’s Bench: The Principles and Building of SSB Gear” started in QST in September 1985. There were at least five parts — it continued until January 1986. (Links to the series appear below.) I hadn’t looked at these articles in years, but when I did, a big mistake jumped right out at me: In the first installment, on page 19, Doug makes the same mistake that he made in his Design Notebook:

“Now comes the conversion section of our SSB generator. We must move (heterodyne) the 9-MHz SSB signal to 3.75-4.0 MHz. Our balanced mixer works just as it does in a receiver. That is, we inject the mixer with two frequencies (9 MHz and 5 MHz) to produce a sum or a difference output frequency (9 – 5 = 4 MHz, or 9 +5 = 14 MHz) If we are to generate 75 meter SSB energy, we must chose the difference frequency. We could build an 20-meter SSB transmitter by selecting the sum of the mixer frequencies. The RF amplifiers and filter (FL2) that follow would then have to be designed for 14-MHz operation. In fact, many early two-band homemade SSB transmitters were built for for 75 and 20 meters in order to use this convenient frequency arrangement. The use of upper sideband on 20 meters and lower sideband on 75 meters may be the result of this frequency arrangement (the sidebands become inverted when switching from the difference to the sum frequency.) ”

Those last two sentences are incorrect. They repeat the “Myth,” or the “Urban Legend” about the origins of the LSB/USB convention. Contrary to what many hams now believe, with 9 MHz filter and a 5.2 MHz BFO it takes more than just switching from sum frequency to difference frequency to invert one of the sidebands.

There are two conditions needed for sideband inversion to take place:

1) You have to be taking the difference product (DeMaw got that right)

2) The unmodulated (VFO or LO) signal must be larger than the modulated signal. (DeMaw and the ARRL obviously missed that part. Repeatedly.)

This is another way of stating the simple, accurate and useful Hallas Rule: Sideband inversion only occurs when you are subtracting the signal with modulation FROM the signal without modulation.

For DeMaw’s claim to be correct, one of the SSB signals going into the balanced mixer would have to invert, and the other would have to not invert. Let’s see if that happens: He has the sideband signal being generated at 9 MHz and the VFO running around 5 MHz.

9 – 5 = 4 But we are not subtracting the modulated signal FROM the unmodulated signal. SO NO INVERSION

9 + 5 = 14 We are not subtracting at all. SO NO INVERSION.

Doug’s convenient frequency scheme WOULD work if he’d just switch the frequencies of the filter and the VFO. With a sideband generator on 5.2 MHz and a VFO around 9 MHz you do get the happy 75 LSB, 20 USB arrangement without the need to switch the carrier oscillator/BFO frequency. That is what happened in the Swan 240, and that is what I have in my Mythbuster rig. I am listening to both 75 LSB and 20 USB without changing the carrier oscillator/BFO frequency. My filter/BFO/product detector is set up for USB. With this arrangement the 75 meter LSB signals DO invert, and the 20 meter USB meter signals do not, so both are able to make use of my USB BFO/product detector without shifting the BFO frequency.

This error shows up again in DeMaw’s the May 1989 QST article “A Four Stage 75-meter SSB Superhet” (reprinted in the ARRL’s QRP Classics book). Here he writes:

“Should you want to cover both the 75- and 20-meter bands you can build a 20-meter version of FL-1 and band switch the two filters. As with the 75 meter only version, an IF of 9.0 MHz (Y1) is required. With this arrangement the 20 meter band will tune backwards from the 75 meter band, but upper- and lower-sideband reception will occur, as required, without changing the BFO frequency (Y2). This two band scheme with a 5-MHz VFO is an old one!” NOTE: FL1 is the bandpass filter, not the IF filter.

Doug’s mistakes in this area may simply be due to the fact that he was more of a CW guy. And this is something that is quite easy to confuse: 9 and 5 will get you to 75 and 20, but you have to make sure the VFO is at 9 if you want to make use of sideband inversion and avoid having to shift the BFO/ carrier oscillator. I’ve made this mistake myself:
https://soldersmoke.blogspot.com/2012/05/usblsb-urban-legend-debunked.html

In October 1993 I wrote to DeMaw about his Four Stage 75 meter SSB Superhet. I think I was looking for details on how to put it on 20 meters. As I recall, Doug wrote back telling me to just pick 20 meter values for the input bandpass filter. Had I done so, I would have discovered that — for the reasons cited above — this just wouldn’t have worked on 20. His BFO and filter were set up to receive LSB signals. That’s fine for the incoming 75 meter LSB signals. But on 20 — contrary to DeMaw’s thinking — there would be NO sideband inversion. I’d be trying to listen to 20 meter USB signals with a receiver set up for 20 meter LSB.

Did anyone else notice these errors. Were there ever errata notices in QST on this?

This is a reminder that you should take all technical articles and schematics with a grain of salt. Many contain errors. We are all human, and this is a complicated subject with lots of details.


https://pe2bz.philpem.me.uk/Comm/-%20ARRL/Build-Service-Design/Receivers/PrincipleOfBuildingSSBgear/8509017.pdf




The Unicorn! A 75 LSB /20 USB Receiver (That Can’t Work)

Don’t get me wrong — I’m a huge fan of Doug DeMaw. His books and articles are a treasure trove for ham radio homebrewers. Also, Doug was an honest guy who admitted in the preface to his QRP book that at times he did not fully understand the circuits he was building; that kind of honesty is rare, and is very helpful to amateurs who struggle to understand the circuits we work on.

But everyone makes mistakes, and Doug made one in his “W1FB Design Notebook.” I present it here not as a “gotcha” effort to nitpick or sharpshoot a giant of homebrew radio, but because this error illustrates well the depth of the 75 LSB/20 USB myth, where it comes from, and how important it is to really understand sideband inversion. Here is the mistake:

That’s just wrong. A receiver built like this will not allow you to listen to 75 LSB and 20 USB “without changing the BFO frequency.” (Am I the first one to spot this error? Didn’t anyone build this thing, only to discover that it, uh, doesn’t work?)

Here’s a little drawing that I think illustrates why the mythical scheme will not work:

All confusion about sideband inversion could be avoided with the simple application of what I think we should call “The Hallas Rule”:

“Sideband reversal occurs in mixing only if the signal with the modulation is subtracted from the signal that isn’t modulated.”

Be careful here: I think some arithmetic carelessness is responsible for much of the myth. Taking the difference frequency is not enough to produce sideband inversion. Read the Hallas Rule carefully: For sideband inversion to occur, the signal with the modulation must be subtracted FROM the signal without the modulation.
———————————————
About the Swan 240’s SSB generation scheme:

I first stumbled on this problem when building my first SSB transmitters in the Azores. I was using a VXO, and a filter pulled out of a Swan 240 (5.173 MHz). I started with VXO crystals at around 12.94 MHz. The rig worked, but I couldn’t pull the VXO crystals very far. So I switched to crystals at around 23.3 MHz (you can pull higher frequency crystals farther). But look what happened: My Carrier Oscillator frequency had been set up to receive USB signals on 17 Meters. With the 12.94 MHz rocks, that worked fine: 18.150-12.977 = NO INVERSION. But it all changed when I went to the 23 MHz VXO rocks: 23.323-18.150 = INVERSION! This had me scratching my head a while. I had to draw myself little spectrum pictures (like the one above) before I realized what had happened. To get it to work — to get it to produce USB on 17 meters — I had to move the Carrier Oscillator to the other side of the passband. Good thing that Swan 240 came with TWO BFO crystals (5.1768 MHz and 5.1735 MHz). I just had to change the crystal.

For 75 and 20 meters, the Swan 240 uses the correct 5.173 MHz filter with a 9 MHz VFO to get the happy situation of 75 meter LSB and 20 Meter USB WITHOUT changing the BFO/Carrier Oscillator frequency. This is the Mythbuster scheme. Unlike Doug’s receiver, it works. The scheme also works in the Swan 240 on 40 meters because for 40 the Swan rig has the VFO running from 12.073 MHz to 12.513 MHz. Here too, no change in the BFO/Carrier Oscillator frequency is needed. But the Swan recommended a modification that would allow operation on 20 LSB and 75/40 USB! It used a BFO/Carrier Oscillator crystal of 5.1765 MHz and a switch mounted on the front panel. Luckily, my junker Swan (acquired from HI8P in the Dominican Republic) had the second crystal — mine was 5.1768 MHz. It was that crystal that allowed me to get my Azorean SSB transmitter to work using the 23.9 MHz VXO rocks.

Mythbuster Videos 8 and 9 — The Old Military Radio Net plus “Zero Beat and The Vertical Skirts”

I like to listen to the Old Military Radio Net on Saturday mornings. This week I was listening with the Mythbuster receiver. The AM carriers provided a good opportunity to observe the effects of the steep skirts of the 10 pole crystal filter. We start at zero beat, with the BFO exactly on the carrier frequency. If I turn the VFO dial in one direction, I in effect move the passband in a way that puts the carrier in the passband. And it is no longer zero beat with the BFO, so we hear the heterodyne (the beat!). But if I turn the VFO dial in the other direction, the carrier is now outside the passband. Even though the BFO would produce a tone, we don’t hear a tone, because those steep filter skirts are keeping the carrier out. We do continue to hear some of the sideband frequencies, because they remain in the passband. The very sharp drop-off of the carrier tone is a good indication that the steep skirts of the crystal filter are doing the job.

“Zero Beat and the Vertical Skirts” Sounds like the name of a Punk Rock band, doesn’t it? Anyway in this video I explain what happened in Mythbuster Video #8 (above). I explain why we can hear the Old Military Radio Net carriers when I tune the VFO in one direction, but not in the other.

Mythbuster Video #2 — 10 Pole Crystal Filter

This is a 5.2 MHz crystal filter. I used the G3UUR method for determining the crystal’s motional parameters. I then used Dishal and AADE software to design a 10 pole Cohn Min-Loss filter. I tested the bandwidth with an Antuino Scalar Network analyzer (thanks Farhan!) and a NanoVNA. I found the passband to be a bit tight for SSB, so I replaced the capacitors with caps of a slightly lower value — this broadened the passband. It is still a bit tight, but the SSB audio — while not enhanced or Hi-Fi — sounds fine.

Passband filter shape as seen in the Antuino and in the NanoVNA. The -20 db line in the Antuino actually corresponds to no loss.


The schematic provided by the AADE software. Dishal software may have come up with better, more correct values for the capacitors.

The passband as predicted by AADE. Skirts so nearly vertical as to strike fear in the hearts of SDR owners!

Filter under construction — waiting for the caps from Mouser.

First scan with the NanoVNA. Insertion loss looks very high but that is only because I am terminating the filter with resistors — I just wanted to see the passband shape.

A Video Series on the Mythbuster 75/20 Rig — Video #1

I am happy to report great progress on the Mythbuster project. I have the receiver working on both 75/80 and 20 meters. And it in fact inverts the 75 meter LSB signals, turning them into 5.2 MHz USB signals for passage through my 5.2 MHz USB filter/BFO combo. No switching or shifting of the BFO is needed.

I am following Farhan’s BITX20 advice — I have paused in the construction and am enjoying the receiver that I have built. I’ll build the transmit circuitry later.

Inspired by Frank Jones (you really should be reading the FMLA articles) I have this rig prototyped “Al Fresco” on a pine board that I found discarded on a neighbors front stoop.

There is no RF amplifier in this rig. Following the advice of multiple receiver gurus, I ran the BP filters right into the ADE-1 diode ring mixer. I have the TIA amps set at about 24 dbm. There is a lot of audio gain from the LM386 and the audio pre-amp. This seems to be enough, even on 20. I hear the band noise when I connect the antenna on both 75 and 20.

Here is the first video in the series. I’m posting them first on Patreon, then, a few days later, here and on the YouTube channel.

The Stubborn Myth about USB and LSB

It has been repeated so often and for so long that many of us have come to believe it. I myself believed it for a while. Like many myths, it has a ring of truth to it. And it is a simple, convenient explanation for a complex question:

Why do ham single sideband operators use LSB below 10 MHz, but USB above 10 MHz?

Here is the standard (but WRONG) answer:

In the early days of SSB, hams discovered that with a 9 MHz SSB generator and a VFO running around 5.2 MHz, they could easily reach both 75 meters and 20 meters (True). And because of sideband inversion, a 9 MHz LSB signal would emerge from the mixer as an LSB signal (True), while the 20 meter signal would emerge — because of sideband inversion — as a USB signal (FALSE!) That sideband inversion for the 20 meter signal explains, they claim, the LSB/USB convention we use to this day.

Why this explanation is wrong:

There is a very simple rule to determine if sideband inversion is taking place: If you are subtracting the signal with the modulation FROM the signal without the modulation (the LO or VFO) you will have sideband inversion. If not, you will NOT have sideband inversion.

So, you just have to ask yourself: For either 20 or 75 are we SUBTRACTNG the Modulated signal (9 MHz) from the unmodulated signal (5.2 MHz)?

For 75 meters we have: 9 MHz – 5.2 MHz = 3.8 MHz NO. We are not subtracting the modulated signal from the unmodulated signal. There will NOT be sideband inversion.

For 20 meters we have 9 MHz + 5.2 MHz = 14.2 MHz. NO. No subtraction here. No sideband inversion.

So it is just arithmetically impossible for there to be the kind of happy, easy, and convenient USB/LSB situation described so persistently by the myth.

———————————

We discussed this several times on the podcast and in the blog:

https://soldersmoke.blogspot.com/2015/05/sideband-inversion.html

https://soldersmoke.blogspot.com/2012/05/usblsb-urban-legend-debunked.html

This myth shows up all over the place:

We see the myth here:

http://n4trb.com/AmateurRadio/Why%20The%20Sideband%20Convention%20-%20formatted.pdf

Here the web site owner warns that this is “highly controversial.” Really? Arithmetic?

http://9m2ar.com/lsb7.htm

The myth is very old. Here is a clip from a 1966 issue of “73” magazine:

https://worldradiohistory.com/Archive-DX/73-magazine/73-magazine-1966/73-magazine-01-january-1966.pdf

Finally, to my disappointment, I found the myth being circulated by the ARRL, in the 2002 ARRL Handbook page 12.3:

The fact that the Handbook attributed this to a desire to “reduce circuit complexity” by not including a sideband switch should have set off alarms. We are talking about hams who built their own SSB rigs, usually phasing rigs. A sideband switch would not have added significant circuit complexity. I think they could have handled it.

It is interesting that earlier ARRL Handbooks do not repeat this myth. I found no sign of it in Handbooks from 1947, 1959, 1963, 1973, and 1980. And I found no sign of it in several editions of that great ARRL book “Single Sideband for the Radio Amateur.”

For my next homebrew rig, I will build a rig that DOES do what the myth promises. I will have the SSB generator running on 5.2 MHz USB. The VFO (out of an old FT-101) will be running around 9 MHz. So for 75 meters we WILL be subtracting the signal with the modulation from the signal without the modulation: 9 MHz – 5.2 MHz = 3.8 MHz. There will be inversion. This 75 meter signal will be LSB. For 20 we will just add the 5.2 MHz USB signal to the 9 MHz VFO. There will be no inversion. We will have a USB signal on 20. I’m thinking of calling this new rig “The Legend.” Or perhaps, “The Mythbuster.”

M0NTV’s Latest FB SSB Transceiver

Wow, Nick has a really wonderful rig and has made this great video to explain it.

Elements that I really liked:

— The simple mic and compression. Very nice.
— Termination Insensitive Amps. TIAs Rule!
— Grey Altoid-like boxes.
— Diplexers! Yes!
— Doug DeMaw S-meter.
— No AGC.
— Pentium CPU cooling fan.
— References to EI9GQ (I must get his book!)
— Al Fresco! Good luck with boxing it up Nick.

Bill N2CQR Talks to Dean KK4DAS about the Simple SSB Group Build

Dean KK4DAS visited the N2CQR SolderSmoke shack. We talked about a lot things including chess, Mars, and AI. Dean is an amazing guy — he used to work at NASA’s Jet Propulsion Laboratory and a couple of times actually spoke with Richard Feynman. We also shot a video about the Vienna Wireless Society’s group build of Pete Juliano’s Simple SSB transceiver (video above).

This group build all started with Dean’s build of Pete’s rig. He built his early in the pandemic, while on furlough from work, thus the name “The Furlough 40.” That makes all of this very much a quarantine effort. As we have learned, dark clouds often do have silver linings.

For more details on the group build, check out Dean’s blog:
https://kk4das.blogspot.com/
And here is the Vienna Wireless Society’s Group Build page:
Thanks Dean! And three cheers for all the Vienna Wireless builders!

SolderSmoke Podcast #230 is available! Apr 1, Mars, Group Build, SDR, SSB, Mich Mighty Mites, Mailbag

SolderSmoke Podcast #230 is available for download

http://soldersmoke.com/soldersmoke230.mp3

N2CQR was down for maintenance
A few words about April 1
China lands on Mars
Brood X Cicadas arriving in NOVA

Pete’s Bench
The Dentron Project
The Spillsbury Tindall SBX-11A
KK4DAS and the Simple SSB Group Build
TenTec mods
Shack Mystery solved. Maybe
Changing the channels at age 9

Bill’s Bench
Why LSB below 10 MHz? The “SSB Legend” Rig
WU2D RTL-Dongle Up converter
Understanding the Gilbert (Jones) Cell
SDRSmart RTL-SDR.com V3 Dongle
VK3HN and 2 meter SSB
Jack NG2E, MMM and the 10 minute transmitter
KD4EBM sends me SST by Wayne Burdick. DX!
A new computer

Mailbag:
MM0ACN
VK2EMU
N5VZH
VE3KZJ
HS0ZLQ
AD0JJ
VK8MC
KK0S
VE3VVH
KB3SII
WA9WFA
M0NTV
W2DAB


60 Minutes Story on Mars Ingenuity Helicopter:

Argentine SSB (BLU) Homebrew from Guillermo LW3DYL

Really nice work. BLU is Spanish for SSB. (Juliano BLU?)

But I think Guillermo needs to build ONE MORE BOARD! A VFO or a VXO. Analog. To finish the job. Guillermo tells me this is in the works — he selected an IF of 11.0592 MHz specifically so that he can use a variable oscillator built around a 4 MHz ceramic resonator.

Complete schematic and PC board patterns on his site:

https://qrplw3dyl.blogspot.com/2021/04/transceptor-blu-para-40-metros.html?fbclid=IwAR0BLMVfVTxMlVy1WyUovVJ0FVrrkMulFxeuu24lkjdkW8j-6QX5g_yV05o

Click on the Bloc Diagram for a Better View:

Homebrew Lives! TWENTY N6QW Simple SSB Transceivers Under Construction in Northern Virginia

IF strip by Don KM4UDX
This has to be one of the most successful of SSB group-build projects. Dean KK4DAS has been leading 20 members of the Vienna Wireless Society in the construction of N6QW’s Simple SSB Transceiver, with Dean’s “Furlough 40” additions. This is very FB, and very encouraging. Dean clearly has The Knack. Just two winters ago I was smuggling a 3.579 MHz crystal to Dean for use in a Michigan Mighty Mite. He has clearly made a lot of progress.
————————-
Dean writes:
It has been just over a year since I completed my initial build of the Furlough 40 with much coaching and assistance from Pete. Mike and Don are two out of 20 members of the Vienna Wireless Society Makers group that is working on a group build the SimpleSSB project as enhanced by me to include features like CAT control for digital modes. Beginning about six weeks ago the group is progressing module by module per SolderSmoke best practice advice. We started with the audio amplifier, followed that with the Arduino/SI-5351 based controller module and the builders are just completing the IF module. This week at our weekly meeting, Mike proudly showed off his success.

————————-

Read all about it, and see some really great videos here:

https://kk4das.blogspot.com/2021/04/homebrew-lives-furlough-40-simplessb.html
Leon NT8D’s Front Panel

Hodgepodge: Moving the Carrier Oscillator Frequency (and a Flashback to 2002) (Video)

As explained in the video, in the course of using my RTL-SDR dongle I noticed that the signal being put out by my Hodgepodge rig had some problems. There was poor opposite sideband rejection, and in terms of audio quality I has putting out too many lows and too few highs. I figured the problem was the result of the carrier oscillator frequency being a bit too low, a bit too close to the flat portion of the crystal filter passband. I needed to move that carrier oscillator frequency up a bit.
BITX40 Module BFO
In the actual BITX40 Modules, L5 was replaced by just a jumper wire, and the C103 trimmer was not on the board. Farhan and his team instead selected X5 crystals to match the passband of the 12 MHz crystal filter. Mine was originally at 11.998653 MHz. But I wanted to tweak mine a bit — I wanted to move it up about 500 Hz. Reducing the capacitance would move the frequency up. Putting capacitance in series with C102 would have the effect of reducing the capacitance in the circuit. I just removed the jumper wire and used the holes for L5. First I put in a single 30pf capacitor. This dropped the capacitance between X5 and ground to 18 pf. That resulted in too large a shift. So I added another 30 pf cap in parallel with the first one. This resulted in a total capacitance from X5 to ground of 26 pf. This was about right — the carrier oscillator/BFO frequency was now 11.9991 Mhz. I had moved the carrier oscillator frequency up by 447 Hz — just about what I was hoping for.

This was a very satisfying fix. it was a chance to put to use experience with other SSB rigs, to make use of the RTL-SDR dongle as a diagnostic tool, and to tinker with the BITX40 Module in the way that Farhan had intended for it to be tinkered with.

I’d done this kind of adjustment before, but without the benefit of an SDR display. Below is the story of one such adjustment.

———————————

A Flashback to 2001-2002
(From my book “SolderSmoke — Global Adventures in Wireless Electronics”)

Now it was time for some debugging and fine tuning. I needed to make sure that the frequency of the carrier oscillator was in the right spot relative to the passband of the crystal filter. If it was set too high, the filter would be chopping off high notes in my voice that were needed for communications clarity, and it would allow too much of what remained of the carrier (residuals from the balance modulator) through. If it was set too low, the voice signal transmitted would be lacking needed base notes. I didn’t have the test gear needed to perform this adjustment properly, but my friend Rolf, SM4FQW, up in Sweden came to my aid.

One night, during a conversation with Rolf, I explained my problem and he offered to help me make the adjustments… by ear. Performing an electronic version of open-heart surgery, with power on and Rolf on frequency, I opened the case of the new transmitter. The carrier oscillator has a small capacitor that allows the frequency of the crystal to be moved slightly. With Rolf listening carefully, I would take my screwdriver and give that little capacitor a quarter turn to the right. “Better or worse?” I would ask.

I think this little adjustment session captures much of the allure of ham radio. There I was, out in the North Atlantic, late at night hunched over a transmitter that had been forged from old Swans and Heathkits, from cell phone chips, and from bits of design from distant members of the fraternity of solder smoke. Pericles, the source of many of the key parts, was gone. So was Frank Lee, the amateur whose SPRAT article had inspired the project. But Rolf and I carried on with the core tradition of the radio fraternity: hams help their fellow hams overcome technical difficulties.

ZL2CTM’s Simple SSB Transceiver

Congratulations to Charlie Morris ZL2CTM for his first contact with his Simple SSB rig.
There are so many cool things in Charlie’s video, starting with his mention of having been woken up early (2 am) by the very strong earthquake off New Zealand. Exhibiting true homebrew spirit, Charlie apparently went straight for the shack and worked on his rig. FB OM.

Al fresco! I love the spacious layout on the board and the obvious division into stages. And I like the wooden board that holds it all together.

I like the idea of two bandpass filters — this is simpler than switching one from transmit to receiver.

Hooray! Homebrew diode ring mixers! Yes!

I think Charlie follows the UK convention with his T/R switch — they have up as off. I may be wrong but I think most US homebrewers have up as on, and up as transmit. Cultural differences.

Notice Charlie touch-testing the heatsink during that first QSO. We all do that.

I like the 24 volts on the IRF-510 drain. Allison always said that IRF-510s run better at 24V than they do at 12V.

Of course I disagree a bit on the issue of analog VFOs. But this is just a matter of personal circuit preference.

Charlie’s calculations and notes are really wonderful. His candid discussion of impedance matching is especially useful. I think his use of loose-leaf sheets of paper is wise and it paves the way for a useful folder for each HB rig.

Here is the introductory video for Charlie’s Simple SSB project:
Here is Charlie’s 10 part video series on his simple SSB rig:

And here is Charlie’s YouTube channel:
Thanks Charlie!

Glowing Numerals for the Lafayette HA-600A (With Jeweled Movements)

I really like this receiver. I have strong sentimental ties: it was my first SW receiver. But the frequency readout situation was kind of rough — depending on where you put the Main Tuning cap, your Band Spread dial could be WAY off.

China to the rescue! Specifically the very nice San Jian PLJ-6 frequency counter boards. I have used these in several projects. I like them a lot. I get mine on e-bay. They are very cheap. Here is the manual with specs:

https://www.mpja.com/download/35057tebasic%20manual.pdf
As I did with my BITX20, I put mine in an Altoids-sized box. I got to use my Goxawee rotary tool with circular metal blade to cut the rectangular hole. Hopefully future efforts will yield neater results, but the flying sparks were fun; they made me feel like one of those car-part “fabricators” on cable TV.

To tap the VFO frequency, I just put a bit of small coax at the point where the 10 pf cap from the VFO circuit enters the first mixer. I ran this cable to the unused “Tape Recorder” jack on the back of the Lafayette — this connects to the input of the counter. I attached 11 volts from the power supply to an unused terminal on the accessory jack of the Lafayette — this powers the counter.

Having a counter on the VFO proved very illuminating — in more ways than one. I measured the Center Frequency (CF) of my IF to be at 456 kHz. I set the PLJ-6 to display the VFO frequency MINUS 465 kHz. For AM broadcast signals, this worked fine: I’d tune the signal for peak S-meter reading. This meant that the carried was right at the CF.

For SSB, things were a bit different. I set the BFO knob to be RIGHT AT 465 kHz when the dot is in the center position. With the BFO there, I could tune in SSB signals. The suppressed carrier would be right at the center of the IF passband, with the audio information above or below the suppressed carrier frequency. But it didn’t sound good this way — it sounded better if I would tune an LSB signal 2 kHz down from the center, then adjust the BFO down about 2 kHz. This put most of the the audio in the peak portion of the IF filter(s) curve. Doing it this way means that I have to remember that the number displayed on the PLJ-6 is 2 kHz down from the actual suppressed carrier frequency of the transmitting station. I can live with that.

I am going to leave the Lafayette on the corner of my workbench so that I can easily tune in hams and SW broadcast stations. Having modified the product detector and added the digital frequency readout makes listening to this receiver even more pleasing. The jeweled movements are as smooth as ever.

So 2021 is off to a good start on my workbench. HNY to all!

SolderSmoke Podcast #227: Solar System, SDR, Simple SSB, HA-600A, BITX17, Nesting Moxons? Mailbag

SolderSmoke Podcast #227 is available:


http://soldersmoke.com/soldersmoke227.mp3


Travelogue

Mars is moving away. Jupiter and Saturn close in the sky. And the Sun is back in action – Cycle 25 is underway. Also, the earliest sunset is behind us. Brighter days are ahead.


Book Review: “Conquering the Electron” With a quote from Nikola Tesla.


No real travel for us: Hunkered down. Lots of COVID cases around us. Friends, relatives, neighbors. Be careful. You don’t want to be make it through 10 months of pandemic only to get sick at the very end. SITS: Stay In The Shack.


Pete’s Bench and Tech Adventures:

Backpack SDR keithsdr@groups.io

Hermes Lite 2

Coaching SSB builders

G-QRP talk

A new source for 9 MHz crystal filters


Bill’s Bench:

Fixing the HA-600A Product Detector. Sherwood article advice. Diode Ring wins the day. Fixing a scratchy variable capacitor. Studying simple two diode singly balanced detectors. Polyakov. Getting San Jian frequency counter for it.

Fixing up the 17 meter BITX. Expanding the VXO coverage. Using it with NA5B’s KiwiSDR.


Resurrecting the 17 meter Moxon. But WHY can’t I nest the 17 meter Moxon inside a 20 meter Moxon? They do it with Hex beams. Why so hard with Moxons? DK7ZB has a design, but I’ve often heard that this combo is problematic. Any thoughts? I could just buy a 20/17 Hex-beam but this seems kind of heretical for a HB station.


Suddenly getting RFI on 40 meters. Every 50-60 Hz. Please tell me what you think this is (I played a recording).


MAILBAG:

Dean KK4DAS’s Furlough 40/20

Adam N0ZIB HB DC TCVR

Tony G4WIF G-QRP Vids. Video of George Dobbs.

Grayson KJ7UM Collecting Radioactive OA2s. Why?

Pete found W6BLZ Articles

Rogier KJ6ETL PA1ZZ lost his dog. And we lost ours.

Steve Silverman KB3SII — a nice old variable capacitor from Chelsea Radio Company.

Dave K8WPE thinks we already have a cult following.

Dan W4ERF paralleling amps to improve SNR.

Jim W8NSA — An old friend.

Pete Eaton WB9FLW The Arecibo collapse

John WB4GTW old friend… friend of:

Taylor N4TD HB2HB


And finally, we got lots of mail about our editorial. No surprise: Half supportive, half opposed. Obviously everyone is entitled to their opinion. And we are free to express ours. It’s a free country, and we want it to stay that way. That is why we spoke out.


Yesterday the Electoral College voted, finalizing the results. All Americans should be proud that the U.S. was able to carry out a free and fair national election with record turn out under difficult circumstances. And all loyal Americans should accept the results. That’s just the way it works in a democracy.


We are glad we said what we said. It would have been easier and more pleasant to just bury our heads in the sand and say nothing. But this was a critically important election and we felt obligated as Americans to speak out. We’d do it again. And in fact we reserve the right to speak out again if a similarly important issue arises.

Pete Juliano’s Presentation to the 2020 G-QRP Club Convention — Building SSB Transceivers

It is a great day my friends. G-QRP has posted on YouTube the presentations made at their 2020 convention. TRGHS! Above you can see the awesome FB contribution of Pete Juliano N6QW. I watched it live on Zoom, but have been waiting patiently for the opportunity to share it with SolderSmoke readers and listeners.

There are many other great videos of convention presentations on the G-QRP YouTube channel. Here is the link to the channel:
Be sure to subscribe and give many “thumbs up” to the presentations.

I see that our friend Alan Wolke W2AEW has a presentation on the NanoVNA in that channel. FB Alan.

Thanks to G-QRP for running this event and for putting these videos on YouTube.

Adding 10 kHz of Coverage to My BITX 17

Solar Cycle 25 is underway. The Solar Flux Index and Sunspot numbers are up considerably. I have dusted off my old BITX17 transceiver. This time around I am using it in conjunction with a waterfall display provided online by NA5B’s KiwiSDR receiver, which is located about 9 miles east of me. This SDR receiver allows me to see the entire 17 meter band. It was this panoramic display that made me pay more attention to the fact that the Variable Crystal Oscillator (VXO) that I am using in this rig prevented me from tuning the lower 10 kHz of the 17 meter phone band (18.110 — 18.120 MHz).

I use two crystals switched by a relay to cover the band. One is at 23.149 MHz, the other at 23.166 MHz. The crystal filter is at 5MHz. With a coil and some caps I could move the frequencies of the oscillator enough to cover 18.120 to 18.168 MHz (top of the band).

When I first built this thing, I kind of wrote off the lower 10 kHz of the phone band. I couldn’t get the oscillator to work that low, and I was already satisfied with the top 48 kHz. But the NA5B waterfall often showed SSB stations in that lower part of the band. I wanted to talk to them. So I started thinking about how to do this.
Looking at my schematic (above) I remembered that most of the frequency lowering was done by L1, a 3.2uH toroid. I figured that to go a bit lower, I would just have to add inductance. But I didn’t want to lower the frequency provided by BOTH crystals — I just wanted to bring the frequency with the lower crystal down a bit.

In my junkbox I found a 1 uH coil. I disconnected the lower lead of the 23.149 MHz crystal from its connection to the relay. I soldered the 1 uH coil between the crystal and the relay (see picture above). This moved the lower limit down to 18.087 MHz.

Now crystal one provides 18.087 – 18.144 MHz
crystal two provides 18.137 – 18.167 MHz

So now I have the whole phone band. Bob is my uncle. TRGHS.

This was a very quick and satisfying little fix. As Pete says WYKSYCDS: when you know stuff you can do stuff. Indeed. And as I re-build and repair gear that I built years ago, I am often reminded that as time goes by, we learn more. We end up knowing more and being able to do more.

I am also planning on rebuilding my 17 meter Moxon; this time I will make it better and stronger.