Author: Peter Marks

“Analog Man in a Digital World” by OM Joe Walsh (music video)

After seeing my last post about SDR, the dongle, the Android tablet, and the Bluetooth mouse, Bob Keller grew concerned about my, uh, stability. Here is our e-mail exchange.

Bill,

Have you had a comprehensive medical evaluation recently? All this digital activity from an erstwhile analog man is a concerning symptom.

I suggest listening to the following number at least once each day until you have the chance to get checked out:

— 73 de KY3R,
Bob Keller


Bob:

I know. It really is quite disturbing. I’ve been getting a lot of “welcome to the dark side” messages!!!

I am now trying to get back in the good graces of The Radio Gods. Today I fired up the Fish Soup 10 and made two CW SKCC contacts on 40 meters. I feel better already.

Thanks for the song from OM Walsh. I had heard it before but it is more meaningful to me now. I will put it on the blog. Others may need help too.

Thanks for caring Bob.

73

Bill

My Hodgepodged Morse: Audio Tone into the Mic Jack Creates J2A not A1A. BASTA!


In SolderSmoke podcast #229 Pete and I were discussing my rather flaky effort to turn the Hodgepodge BITX40 Module into a CW rig by injecting keyed 700 Hz audio into the mic jack (see video below). We got some very helpful responses from ND6T and VK2EMU:


Hi Bill,

You mentioned generating CW by modulating SSB: Collins did that in their
first SSB transceivers, I believe, as did SGC, but the results were less
than optimal. The problem is that you are involving the audio chain and
modulator. You know from experience how difficult it is to maintain low
intermod there and the tone is no exception. So we end up with lots of
spurs within the filter passband and then also have the opposite
sideband suppression less than perfect. If you check your transmitted
signal with a spectrum analyzer or SDR you can easily see the nasties.
Listening to a CW signal thus generated makes it obvious unless it is
buried way down in the noise. It IS a valid CW signal (not MCW) since it
is (almost) a single signal. However, in actual operation it doesn’t
work very well.

I know because I have done that. I bought one of Farhan’s original
BITX40 boards and wanted to put it on CW. I ended up injecting a keyed
signal from one of the spare clocks on the Si5351 into the RF amplifier
chain (thus avoiding the above stated problems) but still had garbage
from the audio and IF stages. I fixed that by shorting out that signal
during transmit by a transistor to ground. That was documented on your
BITXhacks website: http://bitxhacks.blogspot.com/2017/02/ and on my
website: http://www.nd6t.com/bitx/CW.htm . It has been a while, eh?

…

Don, ND6T

————————————————–

Hi Bill and Pete,


With putting an audio oscillator into you hodgepodge radio, your transmission is not the same as a standard CW rig.


If we have a transmitter as described in the ARRL handbooks from the 1940’s or 1950’s, (or even the Michigan Mighty Mite) it is a crystal oscillator and maybe a PA tube. By keying either the oscillator and/or the final PA on and off, then we can send Morse code as ICW Interrupted Continues Wave. If we check the list of emission designators, we have A1A.


However, if we feed a tone into a SSB transmitter, then we have J2A.


At the other end it may sound the same, but because it is created in a different way, it has a different designation.


A quick look at Part 97 shows that J2A and J2B are classed as CW, so you are in the clear. However, if you put a tone oscillator into an AM signal to send CW, then that would be classed as A2A and not classed as CW, but as MCW. MCW can be used on 6 meters and above, but not HF.


SITS.


73 de Peter VK2EMU

———————————————————–


So I say BASTA with the J2A! If I want to go CW, it’s all A1A for me. I dusted off my Fish Soup 10 and am now back on 40 CW with 200 mW…. A1A all the way!

SolderSmoke Podcast #229 — G2NJ Trophy, SDR, HDR, CW! Mailbag

Soldersmoke Podcast #229 is available:

http://soldersmoke.com/soldersmoke229.mp3


— G2NJ Trophy is awarded to Pete Juliano, N6QW.

— Get your vaccine shot as soon as you can!

— More from “Conquering the Electron” by Derek Cheung.

— Bad fire in the chip factory. Such a shame. Sad! I had NOTHING to do with it. I was home that day. I can prove it.

— Bezos is not such a bad guy. Turns out he is a space-geek.

— Perseverance was the big space news. Very cool.

Pete’s bench:

Raspberry Pi vs. Microcontrollers

Treedix display

Conversion of the Dentron Scout

CW rigs?

6L6 on a wooden chassis


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Bill’s bench:

Hodgepodge:

— BITX40 Module.

— Ramseykit Amp.

— San Jian counter,

— CW using 750 Hz oscillator.

— RF-actuated piezo buzzer.

— SDR! SDR using PC and tablet.

— Checking the output with SDR.

— Moving the carrier osc frequency.

Also, I put the Fish Soup 10 back on the air. Nice contacts under 200 mw.

Up next: A rig for 80/75 and 20 meters. Single Conversion. Using VFO from a Yaesu FT101 that runs 8.7 – 9.2 Mhz. Quiz question: What IF should I use?

MAILBAG

Mark Zelesky sent me wood tokens with power and Ohm’s law formulae. Thanks!

Scott WA9WFA Built a really nice Mate for Mighty Midget RX – getting it going!

Tryg EI7CLB found board of his George Dobbs Ladybird RX. Rebuild it OM!

Tom WX2J – We talked about “No lids, no kids, no space cadets” nastiness.

Nick M0NTV about sideband inversion. I like the simple rule about subtraction.

Jonathan M0JGH – Always listen to Pete. Got married, has mixing product. Leo?

Mike AE0IH. Dad used a BC-348 in the service. Looking for one. FB.

Adam N0ZIB – “Silent Shep” site — with some ham radio shows I had not seen.

Walter KA4KXX in Orlando has a similar subtraction problem with San Jian counter.

Bill N5ALO sent me a really nice KLH speaker. I’m using it now.

Jason N2NLY – interested in building SSB transceiver. One step at a time OM…

Trevor in Annapolis sent xcsd cartoon that really hit home.

Farhan is doing OK in India, diligently protecting his family from the virus.

Peter VK2EMU also doing well.

Dave AA7EE Casually killed a DC receiver in Hollywood, and disposed of the remains.

Charlie ZL2CTM doing great things with simple SSB. Blogpost.

Phil VK8MC in Darwin sends article on “Mend not End” battle against planned obsolescence.

Bob KY3R re my SDR adventures, asked if I’ve had a recent medical/psychiatric evaluation.


Hodgepodge: Tablet SDR with a Bluetooth Mouse (video)

I continue to find things in the shack that I can connect to the Hodgepodge. Here it’s an old Android tablet with a Bluetooth mouse.

The waterfall is pretty, but this addition just shows why SDR is really TOO easy. The modified RTL-SDR dongle is doing direct sampling, so there is not even any phasing circuitry to tinker with. All the filtering and sideband selection is happening in software inside the 40 buck Android tablet. The results look nice, but I don’t find it very satisfying — all I did was connect some cables. So it’s back to HDR for me.

A REALLY Cheap Receiving Rig

Wow, lots of ingenuity in this 1921 receiver.

— Has anyone actually made a diode out of a light bulb in the way described?

— The antenna coupler on the table leg is not much different from the tuner that I have attached to the wall of my car port.

— Note that when our hero finishes the receiver, he is able to pick up signals from Mars! FB OM.

Who will be the first to recreate this 1921 receiver?


Aladdin’s Lamp == The Vacuum Tube (aka The Thermatron) (Video)

After our posting of the video about 1957 transistor production, our friend Peter O’Connell VK2EMU asked for some equal time for vacuum tubes. He sent me this 1940 Western Electric video. It is quite interesting.

— I like the Aladdin’s lamp metaphor. When I was out in the Azores I thought of my homebrew 17 meter DSB rig as my “magic carpet.”

— Lowell Thomas was brought in to narrate. His voice sounds a lot more natural than that used to narrate the transistor film.

— To explain the effectiveness of transcontinental telephony with vacuum tube repeaters, they compared the system that of a relay of “hog callers” claiming that it would take 100,000 hog callers to carry a signal from New York to San Francisco. So perhaps this could be a rival to db? 100,000 hc?

— Arlington to Paris 1915 caught my eye — Arlington Va. is right down the road.

— The film of Edison in his lab was good to see. And note the importance of his lab notebooks.

— The explanation of thermionic emission was quite good. But of course too much credit was given to Lee DeForest.

— The breathless description of the amazing uses of tube technology was for me a reminder of how recent this technology is. My father started as New York City cop in the 1950s. He always referred to his police car as a “radio car.”

Hey, are any radio amateurs out there using one of those big water-cooled tubes? If not, why not?

A Homebrewer

That is Homer Price, the lead character in two books by Robert McCloskey, published in 1943 and 1951. The thing in the valise is Homer’s pet skunk. Of course.

More info here:

Homer is clearly a fellow we need to know more about. I have ordered the book.

Making Transistors in 1957

Thanks to Thomas K4SWL for alerting us to this video — he had it on his excellent SWLing Post blog.

Many things crossed my mind as I watched this video:

— Pocket protectors! Pete recently noted that this was a common fashion accessory among electronic techs and engineers back in the day.

— HP test gear.

— “Extreme cleanliness” that doesn’t seem quite so clean.

— 550 transistors per hour. Now we have upwards of 50 billion on a single chip.

— The Germanium salami that Pete mentioned in our last podcast.

— Hints of Silicon’s impending replacement of Germanium.

— A transistor factory in Spring City, Pa. that “hums with excitement” (seemed kind of sleepy).

— The 1957 assumption that Philco transistors would be in the first orbiting satellite. Then came Sputnik.

— The transistor that moves like a “Gulliver through Lilliputian lands.”

— Our voices or accents seem to have changed, at least the voice used in products like this. No one talks that way today.

— As I watched, I tried to remember if Pete’s CK722 was made by these folks. But no, that was a Raytheon product. Here is a nice short description of the early days of the CK722: https://en.wikipedia.org/wiki/CK722 We need to learn more about the hobbyist Carl Todd.

The Secret Life of LEDs — A new Tim Hunkins Video

Thanks to Tony G4WIF for alerting us to this really nice video from the fellow who made all those great “Secret Life of Machines” videos. This video on LED’s makes me want to improve the lighting in my work shop. And I think I need some more high wattage resistors. I’m really glad Tim Hunkins is making more videos. His look at the Secret Life of Radio was a real masterpiece.

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.

Straight Key Night 2021 at SA2CLC in Sweden

Wow, check out the FB gear of Tommy SA2CLC in Sweden, in use on Straight Key Night 2021. There is some German WWII gear, a BC-348, a homebrew transmitter, and some FB QRP kits.

More on Tommy SA2CLC here: https://www.qrz.com/db/SA2CLC
The culvert under the road for coax to the antennas is very cool.
FB Tommy! A belated HNY to you OM.

AA7EE Casually Kills a Direct Conversion Receiver, then Coldly Discards a Diode Ring Mixer

I was really glad to see that Dave AA7EE has — after a long absence — posted another article on his blog. The article has some great personal reminiscences about his involvement with direct conversion receivers. Here is one passage:

I spent many happy hours tuning around and listening on 80M with the DSB80. It was this first experience that cemented my affinity for direct conversion receivers built with commercially available diode ring mixer packages. It just seemed so simple – you squirt RF into one port, a VFO into the other, and (after passing the result through a diplexer) amplify the heck out of the result. The seeming simplicity of the process of converting RF directly to baseband audio has held great appeal for me ever since. Unfortunately, that project didn’t survive. One day, in later adulthood, in my apartment in Hollywood, I reversed the polarity of the 12V DC supply and, discouraged at it’s subsequent refusal to work, tossed the whole thing away. Now, I cannot quite believe that I did that, but it was during a long period of inactivity on the ham bands, and complete lack of interest. If only I could go back, and not have thrown it into the dumpster of my apartment building! Hollywood is ridden with recent notable history. My little double sideband transceiver met it’s unfortunate end just 100 feet from the spot where Bobby Fuller, of The Bobby Fuller Four, was found dead in his car, in 1966, the subject of a still unsolved mystery to this day. The death of my little DSB rig was a lot less mysterious. To think that I heartlessly tossed an SBL-1 mixer into a dumpster, is a mark of how far I had strayed from my homebrewing roots, forged in a little village in England. Now, a few years later, in a city known for it’s sin and excess, I had cruelly ended the life of a stout and honest diode ring mixer. I suppose I should spare a thought for the polyvaricon but, well, you know – it was a polyvaricon!

https://aa7ee.wordpress.com/2021/03/04/the-ve7bpo-direct-conversion-receiver-mainframe/

EXORCISM! 40 Meter RFI Problem Resolved

BEFORE

David W. suggested I use my RTL-SDR dongle to look for the source of the 40 meter RFI that I have been mentioning. (It appears as an ugly stipe in the waterfall of my Hodgepodge transceiver.) So I fired up the RTL-SDR — there were the tell-tale spikes, spaced neatly every 50 kHz. The ARRL Handbook says this is typical of a switched power supply. Before I started patrolling the neighborhood with a tin-foil hat and a portable receiver, I decided to check my own house for any recently installed electronic devices. It didn’t take long — when I unplugged the new (mid-pandemic) treadmill the spikes disappeared. This treadmill was located about ten feet above my rigs, and between the rigs and the antenna. Duh. I should have thought of this earlier. Mystery solved. Thanks David.

AFTER

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!

Over the Waterfall into the Dark Side: Hodgepodge SDR

This one’s for Pete. My effort to add features and modes to my Hodgepodge transceiver took a dramatic turn when I connected the rig to my computer via an RTL-SDR dongle. Woohoo! A Hodgepodge waterfall! Check it out.
The dongle was modified for direct sampling at HF. In the box with the dongle I have one amplifier stage, consisting of a 40673 dual gate MOSFET and one parallel tuned circuit, now tuned to the Hodgepodge IF of 11.998 MHz. I tap the the Hodgepodge’s BITX40Module at the output of the first mixer, just before the crystal filter. This was a lot of fun. I can even check my own signal on transmit! This is like having the best of both worlds.