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Friday, March 29, 2024

A QRP CW Contact (Video) with the Winterfest MXM SupeRX/TX 40 (1 Watt, Crystal Controlled Transmitter)

I picked this transceiver up at Winterfest for one dollar. 40 meters. Superhet receiver with 455 kc ceramic filter and 2 NE602s. Crystal controlled one watt transmitter on 7039.5 kc. I emailed Jeff KA2BKG and asked him to slide up a bit to my freq. I am glad he did. Thanks Jeff.

Wednesday, March 27, 2024

KD0FNR's Amazing San Francisco TouCans Rig -- A Rockmite and a Tuna Topper in a Pineapple Can Mounted on the Dipole in a Shopping Bag

Click on the image for a better look

This post has a definite San Francisco vibe. 

Hamilton KD0FNR appeared on the SolderSmoke blog way back in 2011.  Perhaps he should join forces with N6ASD who lives quite close to him in SF, and seems to share radio interests.  Also in their area is the esteemed Bay Areas blogger and homebrewer Dave AA7EE ; Dave recently sounded the CBLA alarm, alerting us to the presence of an intruder on 3579 kHz.  In the process, Dave mentioned the Pt. Reyes Web SDR, the presence of which came as welcome news to Hamilton. Finally, Dave and Hamilton mention the KPH Web SDR, which brings to mind Dick Dillman W6AWO who has been on the SolderSmoke blog several times 

Hamilton and his kids have their rig (a Rockmite and a Tuna Topper in a Dole Pineapple can) mounted at the feedpoint of their dipole (in the red shopping bag above).   They link to it via WiFi and Bluetooth. FB.  Thomas Witherspoon has a nice presentation (by KD0FNR) of the TouCans project on his blog: https://qrper.com/2023/12/field-radio-kit-gallery-kd0fnrs-rockmite-20-and-tuna-topper/ 

Hamilton KD0FNR writes: 

At the moment, the kids whose dad I am, better known as the gang—12, 10, and 8 year-old Diaze, Mota, and Tawnse.. all internet aliases—are big into 20 meters QRP CW with Project TouCans, a Rockmite coupled to a Tuna Topper. The radio and the amp that popped us out of QRPp to plain-old QRP are both housed in a Dole Pineapple can with a tuna can as a cover and antenna mount. The whole rig is still very much mounted in our half-wave dipole! 

Project TouCans consists of a Rockmite feeding a 5 Watt Tuna Topper, all of which is housed in our dipole antenna. The Rockmite has a single crystal bandpass filter on it's rx input. That makes it a pretty wide reciever which is fine, but it's particularly sensitive to its tx frequencies, 14075.5 and 14058 kHz AND—for some reason I have yet to understand—10459 kHz. By watching the SDRs that now—thanks Dave—envelope us here at our home QTH in San Francisco, we can see the frequencies of incoming signals. That information keeps me from responding to 14059 kHz signals in vain.

And now, the headphone repeater: TouCans is completely wireless with respect to the ground. That means there's no power line, no feedline, no keyer lines and no headphone line. Keyer controls are handled via wifi to a Raspberry Pi Pico-W on the rig while audio is brought back to my headphones via Bluetooth. Power is provided by a USB-C battery pack that lives in the rig which is mounted above us in the antenna. (Yes, all of this is becuase I thought feedlines matches and baluns were too mystical and hard to understand years ago. Yes, this has probably all been more work than a balun. Yes, I am still totally enamored of my original design decision. :) ) Anyway, the bluetooth range is about 50 feet and the wifi range is shorter than that. The short of it is—pun not intended—that I can't quite use the rig while I'm in my office. But, I can send CQ to the rig every half minute or so via a memory keyer, then turn on the SDR in my office, and then sprint a bit closer to the rig when someone calls back. (It helps that houses in SF are a bit tiny.) So, SDRs are kinda an integral part of our QTH setup and it's awesome to learn about a new—to us—one! Thanks again!

Tuesday, March 26, 2024

How to Feel Bad about Carrier Suppression (and How to Get Over It)

Version 2 of the 15-10 rig continues to give me trouble.  But I guess it is "good trouble" because I am learning from it. 

You see, after you build an SSB rig, one of the critical alignment steps is the placement of the carrier oscillator/BFO frequency in relation to the filter passband.  (The IMSAI Guy has a good video on this -- see above.)  You want to place this oscillator somewhere on the downward skirt of the passband curve.  This will add to the carrier suppression already done by your balanced modulator.  There will always be some carrier remaining from the balanced modulator -- putting the oscillator frequency on the downward skirt of the filter passband adds to the suppression the carrier remnant.  

But you can't overdo it.   If you place that carrier oscillator frequency too far down on the skirt, you will start to cutoff the low audio frequencies in your transmit and received signals.  You will notice that your once beautiful sounding receiver suddenly sounds tinny and high pitched.  Yuck. 

So you go back to the books and the websites.  You look at the passband promissed by the Dishal software you used to design the filter.  See below:  

Click on the image for a better view

Surely with a passband as nice as that one, you will be able to find the sweet spot where the carrier is suppressed and your audio remains pristine.  

But I couldn't do this with the 15-10 rig.  I was forced to compromise: I had to accept less than optimal carrier suppression for less than optimal low frequency passband coverage.  And here is why:
Click on the image for a better view

The curve above is a much more realistic picture of what my filter passband actually looks like (see NanoVNA picture below).  The curve above is from the AADE software.  I found out that the Dishal software DOES NOT factor in important things like Q or ESR.  Dishal treats all crystals as "loss-less radiators."  So when you get up to 25 MHz where Q is important, AADE and other programs will show you that your passband has become curved.  And you can see how this curvature makes it difficult to get the kind of carrier suppression and audio response we want.  

What my filter looked like in a Nano VNA
Click for a better view

Look, the rigs work OK.  The receivers sound good to me.  The carrier is so far down that no one can hear it.  I have to remind myself that we are using 'SSB-SC" -- suppressed carrier, not eliminated carrier.  I've worked a lot of DX with these rigs.  But still,  I would like to improve the situation.  It kind of bothers me.  Homebrewers will understand. 

I have been experimenting with different balanced modulators.  I started with the simple two diode, single transformer, singly balanced design from Farhan's BITX20.  It works fine.  But I think I get a bit better suppresson from a doubly balanced diode ring.  I may try an NE602 Gilbert Cell.   I may also try to build a higher Q 25 MHz filter using low-ESR surface mount crystals from Mouser.  Stay tuned.  

Thanks to W7ZOI, VU2ESE, WN2A, KA4KXX, KK4DAS, N6QW, W2AEW, and G3UUR for all the good advice and encouragement.  Please put any additional ideas in the comments below.  

Monday, March 25, 2024


Dave AA7EE alerted us to this attack.  Please follow-up by posting reception reports (and triangulations!) in the comments below.  Dave writes:  

Recently, an unlicensed beacon (for which read pirate) has turned up on 3579 KHz. It seems to be located somewhere in the Western US, in the tradition of unlicensed HF beacons dating back to the late 80's that were solar-powered, and located in remote areas of the Southwestern deserts. The very first ones were a cluster of beacons around 4096 KHz (a frequency for which crystals were cheaply and easily available).

Anyway, I am equal parts intrigued and miffed by this latest clandestine operation. Intrigued because of the mystery surrounding all such clandestine operations. Where is it? What does it look like? Who built it, and why? I'm also miffed because, well, dagnabbit - it's on our turf!

It can be heard nightly after dark in the West, on both the KFS and KPH SDR's, in Half Moon Bay and Point Reyes respectively. It sends a series of 22 dits, then the call letters KOK, then more dits.

This is an outrage, a travesty, and a direct assault on the sovereignty of all self-respecting CBLA recruits! I call on all denizens of colorburst land to dust off their Michigan Mighty Mites and other plucky little transmitters, and launch the loud, raucous battle cries of  CQ, CQ, CQ into the ether. We shall fight them on the airwaves, we shall fight them in our radio shacks while drinking hot chocolate, winding toroids, and reading QST. We shall go on to the end. We shall never surrender!

I'm telling you Bill, when the very foundations of our existence are threatened, there is nothing that a colorburst crystal and half a watt from a 2N3053 transistor can't achieve. By golly, we can do this.

Your obedient colorburst servant,


Friday, March 22, 2024

W1QG's Cave Dust Twins (and other Homebrew Rigs -- SDR and HDR)

I kind of arrived at Dick Benson's QRZ.com page by accident, but what a happy accident it was.  There is a lot of homebrew goodness on Dicks page, both SDR and HDR.  

Check it out:  https://www.qrz.com/db/W1QG/

Monday, March 18, 2024

Listen to me talking to Jean Shepherd in 1976. I was 18 years-old.

Wow, here is a blast from the past.  I recently read a good article about Shepherd by A. David Wunsch in the Spring 2022 issue of the AWA Journal. David correctly focused on Shep's obsession with the Heising modulator, and the very negative impact ("Your mother should take you to a doctor!") that this had on his dating life. 

I was telling my wife about this article, and I commented that I had once spoken to Shep during an early morning call-in show on WMCA New York.  I told her that someone had sent me a recording of this brief conversation. 

The call took place in 1976.  Shep was appaearing as a guest on the late-night radio show of Long John Nebel and Candy Jones.   I was 18 years old. My callsign was WB2QHL.  The recording was sent to me by Matt KC8COM in 2006. Thanks Matt!  In 2008 I played the recording during SolderSmoke Podcast #90.  But I think this call merits a post on the SoldedSmoke blog, so here it is.  You can jump forward to about 3 minutes, 49 seconds.   


One side note.  I told my wife that some time after the broadcast, I was once again up early in the morning, kind of absent-mindedly getting ready for work when I heard Shepherd talking on WMCA to some guy about ham radio.  It took me a moment to realize that this was a re-run, and that that guy was me!  

When I first listened to this I didn't realize that later in the recording (around 9:30) another fellow calls in an asks Shep about why he uses CW.  Shep is kind of short with him and ends up advising him to "go back to CB." I should note that in my conversation with Shep earlier in the program,  I told him that I was usually on "40 sideband."  He was nice to me, but said that he was mostly on 20 CW. 

Here is a good Wikipedia article on Long John Nebel: https://en.wikipedia.org/wiki/Long_John_Nebel

And here's one on his wife and WMCA co-host Candy Jones: 

Friday, March 15, 2024

Finishing up (?) Version 2 of my 15-10 Transceiver (Video) -- An Annoying Residual Carrier Problem

Front panel is on. RF PA is installed. Balanced Modulator problem fixed (?) Rig is on the air with about 3 watts, working lots of DX.

But there is an annoying amount of carrier that is still getting through. It is only about .5 watts with sidebands of 100 watts PEP, but it annoys me, and it makes the setting of the carrier frequency in relation to the filter passband very critical: If I set the carrier a bit too far from the passband I get improved carrier rejection (from the filter), but I also lose the lows in both received and transmitted signals -- the RX just doesn't sound as good. I see it in both of the 15-10 rigs (IF of 25 MHz). There is less of it in the 17-12 meter rig (IF of 21.4 MHZ), and none of it in the Mythbuster (75-20 meters) (IF of 5.2 MHz). I am now wondering if this might be a consequence of my using a very high (25 MHz) single conversion IF in the 15-10 rigs. What do you folks think?

From my log: March 7, 2024 PUT VERSION 2 of the 15-10 RIG ON THE AIR! 10S 1528 OK2RZ Jiri – said I was 57! 15S 1539 S52WW 58 Damian. 15S 1602 SP1NQH Stev said I am big signal! 10S S58N 1726Z 10S S58N 1726Z 10S S57S 1728Z 10S IK4GRO Lauro 1735Z 10S W0CJV 1825Z Ft. Collins Gary 10s 2000Zish KK7TV Gary in Randy. Asked what software/microcontroller I was using. 10S KJ5MFF 2015Zish a middle school in New Mexico. KI5MFF control op sent picture


Thursday, March 14, 2024

"The New Essential Guide to Electronics in Shenzhen" A Book Review by Jenny List (with a video from Shenzhen)

This new book looks really good.  Great electronics info, with lots of cultural and linguistic wisdom. 


Jenny's review brought to mind an older SolderSmoke blog post about Shenzhen. In this 2012 video  Bunnie Huang in Singapore talks about getting parts in that city: https://soldersmoke.blogspot.com/2012/08/singapore-knack.html

Thanks to Jenny, Naomi, and Bunnie.  

Wednesday, March 13, 2024

Using the RF Power Amplifier of the BITX40 Module


PA shematic from the BITX 40 Module
Click on the diagram for a better view

C.F. Rockey W9SCH (who alerted us in SPRAT 22 to the chicken sacrifice option) spoke of transistors that exhibit "quantum mechanical necromancy."  Rockey explained that when this happens, "The transistor simply turns up its toes and dies. Not even an Atomic Physicist can tell you why!"  

This often (very often!) happens with homebrew power amplifiers.  So when we find a good one, many of us stick with it, using the same power amp circuit in rig after rig.  I have done this with the power amplifier from the BITX40 Module. 

Mythbuster (75 & 20 Meter) version (early)  
Click on image for a better view. 

Same amplifier built into Version 2 of the 15-10 Transceiver 
Click on image for a better view. 

In the build for the 15-10 transceiver you can see some changes.  I used an RD06HHF1 instead of an IRF-510.  I used an 8.1 volt zener diode instead of the regulator chip. I set the bias at around 5.5 volts DC on the gate of the RD06.   I used a smaller, metal can driver transistor (it works fine). I changed the input/output physical configuration between the pre-driver and the driver stages (I think it was kind of goofy the way I had it in the Mythbuster).  Finally, you can see how I used a small piece of copper tape (with conductive adhesive) to shield the line going from the driver transformer to the gate of the RD06.  The wire was too small to use a bit of shielded coax, but I think the copper tape and the copper clad board beneath it work just as well. 

Farhan provided me with some fascinating background on this circuit: 


I just saw your post on the bitx40 power amp. The credit must go to Wes for this, it is from the Lichen transceiver described in 6.9 of the EMRFD. I merely copied it with some modifications for it to work with junkbox components.

It bears mentioning that at that time I didn't have a way of generating two tone signal or measuring the IMDR. Those came later when I built my own spectrum analyzer based on Wes and Terry White's spectrum analyzer. It was sheer luck that I picked this power chain that already had careful gain distribution.

For the output, the original build used and LPF with inductors wound on a ballpen shell and TV baluns cores instead of toroids. Again, it was incredibly lucky that they worked at all. 

- f

Tuesday, March 12, 2024

Justin's Receiver -- A 40 meter Superhet from AC8LV

FB Justin!  I really like the board that you are using as a base for the project.  And you have some great mentors in Nick and Loren.  

It is wonderful that you have that receiver working.  But I would tweak and peak quite a bit before taking on the transmitter.  Get a decent outside antenna -- even a dipole or a 1/4 wave with counterpoise would be a big improvment.  Like this one:  

And try to square away the grounding on the board (maybe some copper tape from Amazon) and the power supply you are using (I hope it is not one of those noisy wall warts).  When  you are experimenting, it can be useful to power varous stages with 9V batteries -- this is a good way to find out where noise is coming from.  If your AF amp is squealing at 12 volts, you need to break the feedback loop that is leading to oscillation.  Often the feedback is through the power supply.  Finally, try to get that homewbrew crystal filter working -- if the bandpass is uneven, you just need some impedance matching at the input and output.  

Great work Justin!   Keep at it.  73  Bill 


I am sending video and pictures of my 40m  superhet that I built. I have it on the floor in an extra room in the house. The antenna is a stock vhf dipole that came with my rtl sdr which I use as a spectrum analyzer. In one of the clips I am receiving RW7K. I have been working on the station for the past year with help from Loren Moline, WA7SKT through texts when I have a problem. The LO / VFO is from Nick Woods Videos.

Next, I will build an outdoor antenna and the transmitter section. I first started homebrewing at the beginning of the pandemic, but this is by far my largest accomplishment. I would like to thank you and Pete for the soldersmoke videos which have been a great inspiration.

I will send more updates when the transmitter section is finish along with a much longer description of the projects

Thank you

Justin Elliott

Bill, Pete, and Dean 

Thank you for the compliment. Pete, I want you to know, I’m a huge fan and I enjoy the one-liner jokes. I enjoy your contributions to the videos when you’re on Dean. 

Here are pics / videos of my superhet. 

The bandpass filter is a homebrew version of qrp labs design for 40m, I had to add an extra capacitor to get the bandpass where I wanted it. It is 6.9mhz to 7.32mhz. 

Mixer / demods are ade-ask.

The rf amps are kits i bought online, assembled, then used the schematics to replicate. They are the W7OI created and which have been mentioned on the channel

The LO/VFO are arduino driven from Nick Woods (M0NTV) YouTube channel. I believe episode 26

The crystal filter was built for 9MHz, but when I swept it I found the bandpass was saw toothed, so I used a commercial filter that Loren Moline WA7SKT sent. 

The audio amplifiers are a Common Emitter Amp I found on YouTube, I can’t recall the channel and a commercial amplifier, which I can now reproduce as I have the schematics. 

The speaker is a 2W 8 ohm speaker. 


Justin Elliott

Monday, March 11, 2024

Radio Items Picked-up at VWS Winterfest 2024 Hamfest

As always, click on image for a better view

Above you can see what I picked up at the Vienna Wireless Society's 2024 Winterfest Hamfest. 

-- On the left in the blue box is an MXM Industries SuperRX/TX 40 transceiver. It is a kit from a Texas company.   Superhet receiver with IF at 455 kHz.  Crystal controlled CW transmitter on 7040 kHz.  The oscillator works, but so far no receive signals.  I will have to troubleshoot.  Does anyone have a schematic? 

-- Behind the MXM there is a nice box marked "Diode Detector" I opened it up and there is just a solid state diode and a 50 ohm resistor to ground.   Box may be useful. 

-- I got a couple of books: "Weekend Projects" 1979 from ARRL, and "A History of QST -- Volume 1 Amateur Radio Technology 1915 - 2013" 2013 from ARRL. 

-- On top of the Weekend Projects book you see a "Crystal Holder" from Gross Radio of New York City.  W1UJR has some good history on this company:  https://w1ujr.com/written-word/gross-radio-company-circa-1931/  This device seem to be intended to hold in place a raw piece of quartz!  Cool. 

-- To the right of the books there is a serious-looking VFO.  One dollar!  Deal!  It is a CB VFO, but the markings say it puts out 5.44 to 5.99 MHz.  So it should be useful.  The dual speed dial is very nice.  

-- Above the VFO is a nice step attenuator from the "Arrow Antenna" company of Loveland Colorado. 

-- Further to the right are some Electric Radio and Antique Wireless Association magazines that Armand WA1UQO gave me.  Really nice.  The AWA mags have a very thoughtful piece (warts and all) on Jean Shepherd.  And the ER pile has an article by Scott WA9WFA that mentions my work on the Mate for the Mighty Midget receiver.  Thanks again Armand! 

-- I also got some ADE6+ surface mount mixers.  The price was right! 

Thanks to VWS for putting on this great hamfest! 

Thursday, March 7, 2024

The Wizard of Schenectady -- Charles Proteus Steinmetz

Such a beautiful article.   Ramakrishnan VU2JXN sent it to me.  It reminded me of how puzzeled we were when we found "Schenectady" on old shortwave receiver dials, amidst truly exotic locations.  Rangoon!  Peking!  Cape Town!  Schenectady?   Obviously this was due to General Electric's location in that New York State city.  But reading this article, I am thinking that the presence of Charles Proteus Steinmetz had something to do with it. His informal title (The Wizard of Schenectady)  confirmed that we have been right in awarding similar titles to impressive homebrewers. 

Here is the Smithsonian article that Ramakrishnan sent. 


And here is a link to a PBS video on Steinmetz: 


Here is a SolderSmoke blog post about "Radio Schenectady":


Wednesday, March 6, 2024

N6ASD Builds a Zinc-Oxide Negative Resistance Transmitter (and a Spark/Coherer rig)

I saw this video and post on Hackaday this morning:

I got the fellow's callsign from  his Morse CQ.  
It is N6ASD in San Francisco. 

Check this out from his QRZ page: https://www.qrz.com/db/N6ASD

My journey into the world of amateur radio began in a very primitive way. My first "rig" comprised of a spark-gap transmitter and a coherer based receiver. A coherer is a primitive radio signal detector that consists of iron filings placed between two electrodes. It was popular in the early days of wireless telegraphy.

Spark transmitter (using a car's ignition coil to generate high-voltage sparks):

Coherer based receiver (using a doorbell for the "decoherer" mechanism):

When I keyed the transmitter, a high voltage arc would appear at the spark-gap and this produced (noisy) radio waves. The signal would be received by the iron-filings coherer on the other side of the room. A coherer is (usually) a one-shot receiver. You have to physically hit it to shake the filings and bring the detector back to its original state. That's what the doorbell hammer did. It would hit the coherer every time it received a signal. It amazed me to no end. A spark created in one room of my house could make the hammer move in another room. Magic!

Soon after this project, I started experimenting with *slightly more refined* crystal detectors and crystal radio circuits. As most of you would know, these amazing radios don't require any batteries and work by harnessing energy from radio waves. I guess these simple experiments instilled a sense of awe and wonder regarding electromagnetic waves, and eventually, this brought me into the world of amateur radio in 2015.

My main HF rig is an old ICOM IC-735. The only modification on this is radio is that it uses LED backlights (instead of bulbs):

Icom IC 735

With space at a premium in San Francisco, the antenna that I have settled for is an inverted vee installed in my backyard (and it just barely fits). I made the mast by lashing together wooden planks. For this city dweller, it works FB:

I have recently gotten into CW, and it has definitely become my mode of choice.

I'm a self-taught electronics enthusiast and I love homebrewing radio circuits. I'll be sharing more info about them soon.

Thanks for checking out my page. I hope to meet you on the air!



Tuesday, March 5, 2024

A Contact with my Old Azorean DSB Transceiver

I've been thinking about balanced modulators, and I wanted to see how some of my early circuits performed.  So I pulled this OLD Double Sideband rig off the shelf and fired it up. The balanced modulator -- and everything else! - worked fine,  and I soon made contact on 17 meter SSB with Gene, AB9GK. 

This was the first DSB transceiver that I ever built.  I made this out in the Azores, probably in 2000 or 2001.  Years later I had replaced the RF power amplifier with a "JBOT" (Just a Bunch of Transistors) designed by Farhan.  

Over on my YouTube channel a comment came in from my friend Jack:  

"Looking inside and seeing the o-scope probe in place while the radio was on the air reminded me of neurosurgery where the patient is awake and talking while the surgeon probes different brain regions soliciting feedback. Sure, ham radio isn't neurosurgery, but it's not too far at times. Also, you already have rocket science covered."

Here is an article about my build of that first rig:

I think the article captures well the trials and tribulations faced by new homebrewers, perhaps with the twist that comes from being out in the middle of the Atlantic ocean.  

Mike WU2D is having similar fun with his homebrew 10 meter DSB transceiver: 

I was struck by how similar Mike's early QSO experiences were with mine.  We both put our DSB transmitters on the air before they made their way into real cabinets or boxes. 

Here's mine from 2001 in the Azores: 

Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column