A German Builder Makes a 2 Meter Receiver - Warts and All!

First, you probably need to turn on closed captioning, and select autotranslate, probably to English.  This video is worth it. 

This fellow takes on the self-imposed challenge of homebrewing a 2 meter FM receiver.  He builds it on a copper clad board, using what looks like dead-bug construction techniques.  

He is not a radio amateur.  But he should be one, just by virtue if his work on this receiver. 

The board looks a lot like one of our projects.  He even points out the large number of parts that have been removed from the board.  You get the sense that he shares in our common frustration with circuits that for some unknown reason just won't work.  I found myself worried that he might opt to remove ALL the parts from the board -- that is our homebrew nightmare.  

Fortunately, he does not reach this extreme.  He gets the thing to work.  It is still not perfect.  He will go back to it later.  Good idea.  Take break.  Walk the dog or something.   Insight will come.  

It is really great and refreshing to have this kind of "warts and all" "blow by blow" description of a build projects.  Too often the books present projects as if they worked the first time the builder put them together.  This happens very infrequently -- the process described in this video is closer to the norm. 

And it is great to have this project come to us from Germany.  SolderSmoke is dedicated to INTERNATIONAL homebrew radio.  

He uses an MC3361 chip as the demodulator. Here is the data sheet: https://www.nxp.com/docs/en/data-sheet/MC3361C.pdf

Thanks to Rogier PA1ZZ for sending this. 

Here is the builder's YouTube channel: https://www.youtube.com/@12null02

The TinySA Ultra Spectrum Analyser (video)

I got mine this week, and I've been playing with it.  When I spoke to Dean KK4DAS, I asked what he thought the first thing I did with it was.  He guessed that I tried out the greatly improved Resolution Bandwidth.  Good guess, but not quite:  I tried out the  "listening" feature on this SA.  You will recall that the plain-vanilla, non-Ultra TinySA required a hardware mod to allow for listening.  Dean had told me that the Ultra came with a headphone jack.  Indeed.  I fired it up and was able to listen to 1220 AM and also to the FM broadcast stations in the area.  With the FM stations, I'm guessing I was using a form of slope detection (IMSAI guy says it detects AM).   I tried to see if I could see/hear stations on the ham bands -- so far, no luck.  I'm not sure why, but I will work on this.  

The IMSAI guy video (above) does a great job in comparing the TinySA Ultra to a "real" spectrum analyser.   I think it compares very well.  

One note on where I got mine:  I ended up getting it from R&L Electronics, the recommended U.S. dealer for the device.  I had tried getting it (cheap) through AliExpress.  This didn't really work out.  The tracking info from AliExpress showed that the box had made it to my local post office, but I never got it.  It may have been that they just didn't take the complete mailing address from PayPal.  In any event, I was able to get a refund from PayPal, so no loss here.  R&L turned out to be a great source. 

Ultra, of course. 

A Great Book on Oscillators (Analog LC Oscillators) by John F. Rider (Free!)

 

Thanks to Peter Parker VK3YE for alerting us to this wonderful 1940 book.  John F. Rider -- a real hero of electronic literature -- does a great job in discussing the practical aspects of oscillator circuits. 

This excerpt from Rider's foreword gives a sense of the approach taken in this book: 

The book covers a lot of material.  In addition to the standard oscillator circuits, he discussed multivibrators, relaxation oscillators and much more.  There is a chapter on magnetostriction in which he shows that this property is the basis for crystal oscillators AND the mechanical filters that we are familiar with.  In fact he seems to take what we would consider a mechanical filter and put it in the grid circuit of a tube to make an oscillator. 

He discussed the modulation of oscillators. He describes the Heising modulator that caused young Jean Shepherd so much teenage heartache.  

Download the book here: 

https://worldradiohistory.com/BOOKSHELF-ARH/Rider-Books/Rider-The-Oscillator-At-Work-Rider-1940.pdf?fbclid=IwAR3MfTnhXtrxbUFRMYB1nFu1S2lBugdlAHrqnIO6IGnCMntLggGrvCIroFE

Video: E. Howard Armstrong and Early Radio

This is a really wonderful video. It might seem slow to those accustomed to faster-paced YouTube videos, but the information content is very high -- it contains a lot of pictures I hadn't seen before and audio of Howard Armstrong.  

I never knew that the name of the radio company Zenith was derived from the early callsign "9ZN." 

As a Northern Virginian, I like the reference to NAA Arlington.  

I used to live near Yonkers, N.Y.  I remember Warburton Ave.  What a fine shack young Howard had up in that cupola attic.  

The photo of Armstrong's breadboard was very nice.  My Mythbuster is in good company.

QRPers will get a kick out of the newspaper headline "New Radio Marvel Revealed!"  (They cut the power out from 20kW to 5 watts!) 

Thanks again to Dave Bamford W2DAB for sending me the book about Armstrong, "Man of High Fidelity" by Lawrence Lessing.  

Finally, I remember talking to Bruce Kelley W2ICE at hamfests.   He was a great radio amateur: 

https://www.qcwa.org/w2ice-01351-sk.htm

http://www.arrl.org/w1aw-bulletins-archive/ARLX020/1997

Be sure to check out the Antique Wireless Museum's YouTube Channel.  Lots of good stuff there: 

https://www.youtube.com/channel/UCX55peBhzeX1qps_VYXdLBA

We have the famous photo of Major Armstrong,

 but this is the first one I've seen of a slightly younger Captain E. Howard Armstrong. 

SolderSmoke Podcast #228

Soldersmoke Podcast #228 is available: 

http://soldersmoke.com/soldersmoke228.mp3

Of course, no travel.  But vaccines are here so maybe soon we can leave our shacks.

In the meantime:

I’ve been playing chess against AI bots on chess.com.

Netflix recommendation:  The Bureau.   From France. A review from NPR: 

https://www.npr.org/2020/06/22/881642358/addictively-suspenseful-thriller-series-the-bureau-will-keep-you-on-edge

A reading from "Conquering the Electron."  Germanium vs. Silicon.

Bill’s Bench:

The KLH Model Twenty-one II.  Acoustical Suspension.  First receiver WITH A PILLOW!  Bad speaker? Blown AF amp finals.  Hot heat sink.  VBE Multiplier. Desitin.

Tony Fishpool’s recommended LM386 boards.  10 for 11 bucks.  Nice.  They work.  Pictured in the Amazon ad at the upper right of the SolderSmoke blog page.

Putting a digital display on the Lafayette HA-600A

Test gear trouble.  My Radio Shack multimeter getting flaky.  I many need something better.  Auto ranging? My beloved Maplin AF generator died – will have to fix. I need that thing.  Probably a bad chip.  Good thing they are socketed.

I almost forgot about SKN!  But I remembered and I made one contact with the HT-37 and Drake 2-B.    

Pete’s Bench:

Presentation to RSGB on Homebrew.

TenTek Troubleshoot.

Swan 240?  Looking nice.

SDR adventures.

MAILBAG

Bill N8ET sent me some really nice Showa 9 MHz 8 pole crystal filters. 

Kevin AA7YQ Smoke jumper!  Building a hybrid SDR.HDR rig.  Launched blog. FB

Nick M0NTV working on similar HDR/SDR project.  Great video.

Grayson KJ7UM Hollow State Design – Launched a new blog.  Very FB!

Thomas K4SWL of SWL Post blog.  Kearsarge Mountain Transmission system.  And recent events.

Peter VK2EMU Poetry.  CW poetry.

Pete WB9FLW looking at DSB rigs…

Drew N7DA  Feels not like a real ham because he hasn’t built a quad from bamboo. Which type of landscape bamboo is best for antennas?

Ryan Flowers of MiscDotGeek.Com blog is also watching the Tally Ho YouTube videos of Leo Sampson. Wants to put a WSPR beacon on the Tally Ho. 

Joe KF5OWY  Working with diode ring mixers, trying to see the mixer action on his ‘scope. 1 and -1!

Jim AB9CN sent a cool idea about how to do a 20/17 Moxon.

Roy GM4VKI – I thanked him for his article in SPRAT about putting a 2n3904 on the output of an NE602 10P mod.  Brilliant.

Roger Hayward Told him that I really liked his Dad’s recent web site updates.

Farhan – Jokingly cursed me for showing him the Oscillodyne regen of Hugo Gernsback and Jean Shepherd.  “Now I will have to build this!”

VBE Multiplier Makes KLH Receiver "Cool Running"

Yesterday I turned to the SolderSmoke wizards for advice on how to fix my KLH Model Twenty-one II FM receiver.   I had finally gotten the thing working -- it wasn't the speaker, it was the AF amp, probably one of the final transistors was blown.  I replaced the finals and the driver. For the finals I used a TIP29C and a TIP30C.  For the driver a 2N3906.    With this fix the receiver was sounding good, but the heat sink on the AF amplifiers was way too hot. 

If you look at the comments in yesterday's post, you will see some great suggestions on how to fix this problem.  The comments and Google led me to Alan W2AEW's YouTube channel and his video on a circuit called the VBE multiplier.  Voltage Base-Emitter multiplier.  I'd never used this circuit before.  It allows you to adjust the bias on the bases of the two transistors in a push-pull amplifier.  

This morning I built the circuit on a small piece of PC board.  There were just two components: a 10k trimmer pot and a 2N3904 transistor.  

With the little board installed, I adjusted the pot for a 1.2 volt difference between the bases of Q6 and Q7. I ended up with base voltage values almost identical to those called for in the KLH schematic. 

The receiver sounds very nice now, and is no longer on the verge of bursting into flames.  I even made up my own version of the pillow that KLH claimed was necessary for proper acoustic suspension.  

Sometimes it is nice to be able to listen to something other than the chatter on the ham bands. And it is fun to do so with a receiver that you have worked on.  

I even used some Desitin as a substitute for heat sink compound. 

Thanks to Rogier for the receiver, to ZL2DEX, K0EET, W2AEW and David McNeill for the good advice. And to Dale K9NN who sent me a box of parts from which emerged the 10k pot I used in this project.  Thanks guys. 73  

KLH Model Twenty-One II -- Is My Speaker Dried Out?

A few years back Rogier PA1ZZ very kindly sent me a box of electronics parts.  Included was an FM table-top radio with a nice walnut case.  Thanks Rogier! 

I hadn't looked at the receiver in years, but this week I dusted it off and looked it up on the internet.  Turns out that it is kind of famous.  It was produced by the KLH company.  The K stood for Henry Kloss, one of the giants of Hi-Fi audio gear.  Henry appears in the picture below. 

I got the receiver working, but it sounds awful.  It sounds much better with an external speaker, which is disappointing because the internal speaker was the main attraction of this receiver. It even has a little badge on the front panel trumpeting(!) its "Acoustic Suspension Loudspeaker."

I'm wondering if the problem is in fact the speaker.  The cone looks intact, but it seems very dried out.  It has been more than 50 years...  What do you guys think?  Picture above.  Any other suggestions on what to do with this thing, or how to make it sound better? 

Some KLH history:  

https://klhaudio.com/history

https://antiqueradio.org/KLHModelTwentyOne21FMRadio.htm

KLH receiver with pillow

And Now For Something Completely Different: 70cm FM

So there I was, talking to KE5FV on my scratch-built 17 meter BITX, when in walks my son Billy with this walkie talkie.  "Hey Dad, I'm cleaning out my room -- could you use this?"  I'd seen it before but I thought it was some Family Radio Service device that he had picked up.  But no!  It is one of those very cheap Baofeng UV-5R FM transceivers.  I soon found myself scrolling through menus, trying to figure out how to use the strange new appliance. 

I got it on 70cm and soon established contact with a Bill W3HXF -- that was my first ever UHF contact.  We then switched to 2 meter simplex. 

It works fine.   I've been looking for something different.  This could be fun.  Any suggestions on how to make the most use of this thing?

Narrow Band FM on 160 Meters? Using SSB phasing rigs?

On the G-QRP mailing list our British cousins are discussing the use of Narrow Band FM on Top Band.   160 meters has long been used for day-time local "chin wags" in the UK.   Noise, of course, is a factor to consider on 160.  FM would take care of the noise problem.

I was wondering if this would be legal in the USA. This is the kind of question that seems to provoke passionate, sometimes angry reactions.   I think the answer depends on the resulting bandwidth of the signal. 

There was an interesting discussion of this here:

http://www.eham.net/ehamforum/smf/index.php?action=printpage;topic=65481.0

Especially intriguing to me was Tom's comment about the link between Narrow Band FM and the early SSB phasing rigs.   I hadn't heard about that:

---

Title: RE: Narrow Band FM is it legal below 30 MHZ.
Post by: N5EG on January 22, 2010, 11:10:43 AM

---

Hi Tim,

Yes - NBFM is legal. This is actually a hold over from long ago equipment. Back in the olden days phasing SSB exciters could also be adjusted to produce NBFM.

It's a little different than modern FM, in that the signal looks just like an AM signal, except the phase of one of the sidebands is 180 degrees reversed compared to the AM equivalent (doesn't matter which sideband). This gives an angle-modulated signal with +/- 45 degrees phase variation, but also 3 dB of amplitude variation.

While we don't normally like amplitude variation on an FM signal, it has the effect of preventing the generation of the higher order sidebands that true FM produces. A receiver than has a limiter stage doesn't care that much.

The result is that the old phasing exciters could produce this different kind of Narrow Band FM (probably the true meaning of NBFM long ago) that had the same channel width as AM, and a modulation index that's well below 1. Such a signal is compliant with current FCC regulations on HF bands.

-- Tom, N5EG