HF Bandsweep with the Hammarlund HQ-100 (video)

It has been a while since we last did a bandsweep.  Too long.  Here is one using my recently fixed up Hammarlund HQ-100.  Repair details are in recent videos. 

For this bandsweep we cover most of the HF band and even briefly dip down into the AM broadcast band: 

Demonstration of the Hammarlund HQ-100: Radio Marti, 40 meter AM, 40 Meter SSB, 40 meter FT-8, 40 meter CW with and without the Q multiplier, classical music on WRMI, WFAX 1220 kHz AM, WWV 20 MHz, CB!, 17 meter SSB, the 20 meter BS position, the effect of AVC and the Noise Limiter, SSB with the internal BFO and with the Q multiplier as BFO. CW with the internal BFO AND the Q multiplier. 

Be sure to subscribe to the YouTube channel.  

Working On My Old Hammarlund HQ-100 (Part 1)

I like this old receiver, with all its shortcomings.  I picked it up in the Dominican Republic in 1993 or 1994.  I've been using it on AM with my K2ZA DX-100.   It needed some contact cleaner, and I took the opportunity to work on a few of the circuits that were getting kind of decrepit. 

I came to a new understanding of -- and appreciation for -- the Q-multiplier.

While of similar vintage, this receiver is MUCH nicer than the Hallicrafters S-38E: 

S-38E 1957-61 $54.95 5 tubes.  AC/DC, kind of flimsy. 

HQ-100 1956-60 $169  10 or 11 tubes.  Power supply,  regulator,  much sturdier construction

You get what you pay for.   

 In Part II I'll show you how this thing sounds and what it is like to use it for SWL, CW, SSB and AM. 

Scott WA9WFA's Beautiful HBR-13 Receiver (3 videos)

This is Scott WA9WFA's first homebrew construction project.  He did an amazing job on a very complex project:  a 13 tube superhet receiver.  It features plug-in coils for multi-band coverage, dual conversion with IFs at 1600 kHz and 100 kHz, and several regenerative stages.  Scott's construction is top notch. He tells us that he had been working on this receiver for several years, so long in fact that some of his friends began to wonder if it really existed.  Well wonder no more.  Retirement has provided Scott with the time to finish this project. 

I like the way Scott talks about the project in these videos.  He puts it in the context of his long-standing goal of building his own high quality ham station.  With the HBR-13 done, he is more than halfway there.  We all know that the receiver is the hard part.   

I agree with those who say that Scott should keep the plexiglass front panel.  I think it looks very cool.  

In the third video, Scott takes us on a cruise through the 40 meter band.  The receiver sounds great.  Lou EA3JE's booming voice came through quite nicely from far-off Barcelona. 

Congratulations Scott on building a truly outstanding receiver. And on making some great videos. 

There is some additional background info on the HBR-13 in this blog post from back in September: 

https://soldersmoke.blogspot.com/2021/09/the-hbr-13c-homebrew-receiver.html

Super-Regeneration is Super-Strange

Farhan VU2ESE is largely responsible for this.  He has recently been talking about VHF.  (More about this in due course.).  This started me thinking about my failed effort in London to get on 2 meter AM.   My plan was to use the transmit portion of this HW-30 (above) with a 2-to-10 downconverter and my trusty Drake 2-B for receive.  

Tony G4WIF also bears some responsibility:  When I expressed interest in Farhan's VHF work, Tony sent me two articles from SPRAT.  Both of them were about super-regenerative receivers.  

Farhan's comments caused me to pull the HW-30 out of storage.  I started poking around the transmitter.  But then I noticed something:  On receive, the AF amplifier was obviously working.  Then, when I tuned through the 2 meter band, the rest of the receiver seemed to be working too.  I fired up the HP-8640B sig gen on 2 meters and turned on the AM modulation.  Indeed, the old receiver was inhaling!  

This launched me into an effort to understand how super-regenerative receivers work.  There are a lot of really weak explanations out there. You get the distinct impression that the person explaining the circuit does not understand it himself.  This makes explaining it very difficult.  I am not the only one to notice this phenomenon:  Mike WU2D commented on this in one of his excellent super-regen videos.  This one:  

https://www.youtube.com/watch?v=QOhNPLT8R10

Mike very kindly said the operation of this circuit seems like "magic."  I was thinking more in terms of Voodoo.  

Howard Armstrong discovered super-regeneration years after he invented plain old regeneration.  The new discovery came around 1921.

It looks like VHF guru Frank Jones had very early misgivings about super-regeneration.  In his 1934 classic 5 Meter Radio Telephony, Jones seems unenthusiastic about the circuit and about our ability to understand it:  "To explain, simply, exactly how this form of detection takes place is not a simple matter, but some of its characteristics are easy to visualize."  In this book, Jones goes on to predict that super-regens will be superseded (!) by superhets.  Indeed, in his 1961 book VHF for the Radio Amateur there are no super-regen circuits; all the receive systems are down-converters to HF receivers. 

Still, with that HW-30 hissing away right next to me, I feel I need to understand how the super-regen works.  I'm not there yet, but I'm trying.  Here are some good resources: 

A good article from Wireless World 1946:  

http://www.r-type.org/articles/art-285.htm  

A student's write up of his effort to understand: 

https://folio.brighton.ac.uk/artefact/file/download.php?file=597679&view=111191

But the best so far (for me) is from Frederick Terman (one of the founders of Silicon Valley) in  his 1943 classic Radio Engineer's Handbook.  Click on the images for a clearer view. 

I will definitely try to get the HW-30's 5 watt AM transmitter going.  I am not so sure I'll do anything with the receiver.  I think this is a matter of picking your battles and "finding joy."   I didn't find joy in FT-8, so I stopped working with it.  Same with my HA-600A, DX-40 Novice rig.  Same with CW in general.  And the same with SDR.  I suspect that super-regen receivers may also fall into this category.  I mean, let's face it, if you are not fond of ordinary regens, is there any real chance that you will like SUPER-regens?  Even Frank Jones seems to have disliked them.  And there is a reason Howard Armstrong moved on to superhets -- they are better! But still, that receiver is hissing away at me...  Stay tuned. 

Single Transistor Transceiver On the Air

I got my version of the ET-1 transceiver working.  As I described in previous posts, I first got the transmitter and the receiver working separately, each with their own J310 FET (oh the extravagence!) Then I built a switching arrangement that allowed for just one shared FET and very short leads.   I used a 4PDT "push button" switch from an old Ramsey Electronic LC meter. See the last picture for details. I use the tube from a pen to operate the switch (that's the green thing in the picture). 

It is inhaling and exhaling.  My 20 mW signal is being picked up on the Reverse Beacon Network, mostly in New England, but today in North Carolina.  

No contacts yet.  I may have to resort to scheduled contacts.  OM Yingling W2UW was operating during much better propagation conditions (2001), so I don't think I will ever get close to his impressive (23 states!) operating record.  

But it has been fun getting this thing going.  The N0WVA regen design is one of the best and simplest regens I've ever built.  It is really nice --hardly demonic at all.  

I can run the whole thing off one 9V battery. I think it is a cool looking machine. 

Single Transistor Regen Has QSO Potential (Video)

In my previous blog post I'd expressed skepticism about using a single transistor regen on the air.  But over the years I've learned to give new receivers a chance.  They usually don't work perfectly on the first try.  You have to work with them.  It is almost as if you have to peak and tweak a lot in order to get them to properly inhale signals from the ether.  

That has been the case with this little receiver.  I found some silly mistakes in my construction.  And I decided to try some more sensitive headphones.  I ditched the 1000 to 8 ohm AF transformer.  And I added a very small variable cap for fine tuning.  

The results are amazing. See video above. It performs as well as most of the direct conversion receivers I've built. It is remarkably stable.  

I do think I could make contacts with this receiver.   I might eventually go the full ET-1 route and try to do it with a single switched FET, but I think my next step will be to built a single transistor crystal controlled transmitter on the same piece of wood, and try to make some contacts with a two-transistor rig. 

Another Bout of Minimalist Regen Madness

My success with the Fish Soup 10 QRPp transceiver got me interested in further minimalization.  About ten years ago I built a rig presented in SPRAT 108 as the ET-1 by Glen Yingling W2UW.   It re-appeared in modified form as the FETer by G3XBM in SPRAT 137.  

This rig uses just ONE active device, an MPF-102 FET that is switched via a 3 pole double throw switch from transmit to receive.  The transistor is switched.  The receiver is a regen and the transmitter is a very simple crystal controlled one stage oscillator. See: 
https://soldersmoke.blogspot.com/search?q=ET-1  for info on my ET-1 effort. 
The transmitter was the easy part.  I don't think I made any contacts with this thing.  That has been kind of bugging me.  

So I tried it again.  Again, I had trouble with the receiver.  So I looked around for another single FET regen receiver design.   I found one on AA7EE's page.  It was designed by N0WVA:  
https://aa7ee.wordpress.com/2015/02/07/n0wvas-one-fet-regen-optimized-for-ssbcw-sounds-great/

I've had a variometer in my junk box since about 1994. (Given to me by Pericles HI8P. QEPD.) It was time to use it as the coil and ticker for this rig.   I liked the green LED in the source, and the promise that this thing would not oscillate at audio frequencies.  

I built in on one morning.  See pictures. It works.  I can hear CW stations.  But I think I would have a tough time making contacts with this thing.   OM Yingling worked 24 states with his ET-1.  Respect.  

KD4PBJ's Acorn AM Broadcast Band Regen

From Chris, KD4PBJ: 

This is my AM band regen I built during December and early January. 

It uses a 955 acorn tube and is a really hot performer! I can pick up dozens of stations with only a 20 ft piece of wire thrown out my shop window and tied to a nearby tree limb 5 ft off the ground. This is from rural Tennessee where we have no local AM’s. 

It uses a velvet vernier I bought off eBay back around 1999 or 2000 and had saved for a special project like this. 

I’m running filaments off a 6V lantern battery and plates off a type 415 45V battery. 

A nice ham/machinist I met on the Time Nuts list who lives in San Francisco made my insulated shaft couplings. I got the Delrin rod cheap off eBay. He cut them to length, center drilled for 1/4 inch and drilled each end for 2 setscrews.

Video of a REAL Homebrew QRP Contact (by WU2D)

I think Mike's video does a good job of showing what it is really like to get on the air with simple, homebrew QRP gear.   It takes some patience and operating skill.  I guess it is sort of like fly fishing (with home made lures); there are easier ways to catch fish, but they are not as rewarding.   

German Thermatron Homebrew

Michael DF2OK has been melting solder in Germany.  Above is a short video of the first sounds made by an AC-1 replica he built.   Michael notes:  "Yeah, I love these old style radios. You can see nearly everything. :-)  BTW: All without Arduino and other black boxes and chips!"
FB Michael.

During the AC-1 build Michael struggled with a bad tube.  His discovery and resolution of the problem is presented in this video (understandable even to those who don't speak German):



Finally, here is a nice video of Michael's 40 meter regen receiver. Anyone who has built or worked with a regen will understand perfectly this video.  Watch Michael tune in stations while adjusting the regeneration.  Note his demonstration of the lack of hand capacitance. FB Michael!  Thanks!  

AA7EE's Beautiful Sproutie MK II

 

This is almost too much.  Sensory overload is a real risk here.  Go check out AA7EE's amazingly beautiful regen receiver.  On his site he has a masterpiece of a write up, along  with schematics and build photos.  I love the plug-in toroids.    Great work Dave.  Thanks for sharing this with the homebrew community. 

 

Here it is: https://aa7ee.wordpress.com/2015/09/14/the-sproutie-mk-ii-hf-regen-receiver/

 

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Long Delayed Echo on Radio China International

Several people have e-mailed me suggesting that the weird echo I have been hearing on shortwave broadcast stations is in fact one of the fabled "Long Delayed Echoes" that radio amateurs have been hearing intermittently since about 1927.   I was skeptical at first, but -- at least in the case of the Radio China signal -- I think LDE caused by the signal going around the globe several times does explain what I've heard.  Each trip would add a delay of about .133 seconds, and that seems to match what we hear in my recording:  

http://soldersmoke.blogspot.com/2014/08/strange-echo-on-china-radio.html 

Compare that with what K9FIK recorded on 10 meter SSB (thanks Stephen!): 

http://swling.com/blog/2013/10/hearing-the-speed-of-light-dx-double-echo/
(you can listen to the audio on this one). 

It sounds very similar. 

If this is in fact LDE, I'm lucky -- this is pretty rare.   And it is a eerie that I first heard it on on Regen receiver from the 1920s!  Above is a picture of the regen used to study the FIRST LDEs. See: http://folk.uio.no/sverre/LDE/


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SolderSmoke Podcast #165 Arduinos!

SolderSmoke Podcast #165 is available: 

http://soldersmoke.com/soldersmoke165.mp3

September 13, 2014

Workbench Update:  Bill's "Off the Shelf" Regen,  Pete's Boatanchors
Mysterious Echos on Shortwave Signals.  Solve the Mystery.  Please. 
Microcontrollers -- What they can do for you.
Small world:  As a kid, Pete was neighbor of "Digital Dial" N3ZI 
NEWS FLASH: Arduino creator Massimo Banzi was a ham!  
Born in a bar, cheaper than pizza:  The Italian origins of Arduino
Arduino CW generators
No coding skills needed
Arduino + AD9850 = Signal Generator or VFO
Arduinos in the Minma
What the heck is a Shield?
SolderSmoke Mailbag

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Schematic for "Off the Shelf" Regen

NOTE (May 2024) The eagle eye of Walter  KA4KXX spotted an error in this schematic.  The source resistor in the MPF-102 stage should be around 2200 ohms.  Thanks Walter! 

Tony, VE7JUL, wrote in asking for a schematic on the "Off the Shelf" regen.  Here you go Tony.  Nothing fancy or new here.  All the credit goes to Howard Armstrong, Charles Kitchin and Jay Rusgrove! 

Even though they seem much simpler than other receivers, I think regens are in fact more of a challenge than, say, a Direct Conversion receiver.  Be prepared to do a lot of fiddling around with the coil and the tuning and regen capacitors.  Think of that detector stage as a VFO, a VFO that you want to be able to smoothly take out of oscillation. 

Here's a tip on regen debugging:  Once you have it built, hang a high impedance 'scope probe off the drain of the FET and watch the scope/counter as you move the main tuning cap and the regen control.  This will give you a visible indication of where (on the regen control) the stage is going into oscillation.  A freq counter (I have one inside my Rigol 'scope) will let you know what frequency range you are operating on.  You may end up having to make adjustments to the coil, adding or taking away turns to get into the proper frequency range, or to the desired level of feedback.  Pay attention to the phasing of the coil turns.  You may also find yourself adding capacitance in series with the regen and main tuning controls (to reduce their tuning range) or adding capacitance in parallel with the main tuning cap (to lower the entire tuning range if necessary).  

Build it solid and strong!  It is, after all, an oscillator.  Be prepared to do a lot of "noodling"   

Hi Bill,

This receiver with just 4 transistors and no chips looks really interesting to me.  Do you have a schematic that you could either flip to me or point me to?  Getting my hands on some air variable caps may be a challenge, but I can 'noodle' something out on that.

Love the podcast, blog and really enjoyed the SolderSmoke book - thanks for your continuing efforts to share with the amateur radio community.

73/72
Tony

VE7JUL

the little red dot at Coquitlam, British Columbia on what used to be the Clustr map (but is now a Revolver map)

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Shortwave Echo Mystery on Yet Another SW Station. What is this?

A few weeks ago I noticed a strange echo on Radio China International's signal.  If you scroll down a bit you can see my YouTube recording of the problem.  On one of the SWL lists, there was speculation that this problem was the result of a flaw in the RCI digital studio gear.  But then a few days ago I heard it again on RCI -- surely the tech-savvy Chinese would not have let this kind of problem persist for weeks.  

Today I heard the same effect on a very different SW station -- this one an the 24/7 fire and brimstone broadcast that appears at many points on the dial.  The effect is very similar to what I heard on RCI.  

So OK all your shortwave gurus:  What is going on here?

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