A Fishy Rig: Herring Aid Five, Tuna Tin Two, VU2XVR Key

Haunted by a fear of rapid expulsion from the QRP Hall of Fame, I decided that I should immediately do something to establish some form of QRP street cred.  Looking around the shack, I realized that all of the ingredients were there:  My Herring Aid Five Direct Conversion receiver (completed after only 38 years), my Tuna Tin Two transmitter, the VU2XVR key that Farhan gave me, one 7050 kc  FT243 crystal.   I put it all on a piece of scrap plywood. A couple of nice connectors from W8NSA supported the DPDT T/R switch and the coax connector. I keep the receiver LO running all the time.

Now, let's be clear: running 250 milliwatts, rock bound with a Direct Conversion receiver that tunes both sides of zero beat is not for the faint of heart.  The log book does not fill up rapidly. But hey, I made one contact the following morning.  K1PUG said I was 559 in Connecticut.      

Kirk's Herring Aid, Tuna Tin, and Regen Adventures

 

Hello Bill!

 

Just a quick hello from MN to tell you how much I have been enjoying your podcast. Although I have "plugged" your stuff in multiple magazine columns over the years, I'm a bit late getting into the listening game. My current contract job has me doing a lot of driving, however, so I now have several years' worth of soldersmoke to enjoy.

 

Several of the most recent episodes have made it clear that we have covered some common ground in our amateur radio careers.

I was licensed in 1977 at age 15 -- a year after I built my Tuna Tin 2 :) The transmitter was a smashing success. I used it with my Tempo One transceiver, or at the electronics repair shop at a local National Guard base (where my mom worked as a civilian administrator). I would ride my bike to Camp Ripley (only 8 miles or so), and the guys in the signal shop would let me use the shop's Collins KWM-2 HF transceiver (and attached dipole). Other than my efforts, I don't think the KWM-2 got much use...

 

I, too, tried to get the Herring Aid 5 to work, with no luck at all. Listening to your podcast was like being in a time machine of sorts :) I wonder if I got the "sense" of the oscillator secondary messed up? I never did get that thing to make even a sound. I don't have it any longer. The same goes for the TT2. They got "lost" when I stored a bunch of stuff at my dad's place in-between moves, as did a home-brew 4-400A amplifier and a 6146B amplifier for my Ten-Tec Argonaut. Darn!

 

Don't forget about the matching VFO -- the Chopped Beef Slider (CB Slider), which was built into a chopped beef can, of course! I didn't build one, but as I recall it was a diode-tuned 40-meter VFO for the TT2.

 

Your "regen rage" and its subsequent easing was also amusing. I have had a love-hate relationship with those buggers, too, although mine was mostly love. You referenced Dave Newkirk's (now W9VES) 40-meter QST regen article in a podcast. I was fortunate enough to be a QST editor at the time Dave was in his "second residence." That guy forgot more about receivers than I will ever know, and he helped me tremendously in official and unofficial capacities.

I have attached a photo (above) of a multiband regen that Dave helped me build (he designed and dispensed wisdom while I built the radio). He took a schematic from a 1930s ARRL Handbook and tweaked it a bit, helping me add a VR tube, "more modern" tubes and a few other goodies. Just to be difficult, I sampled the tank circuit with a tiny-value capacitor and a high-gain MMIC amplifier so I could drive a frequency counter, which displayed the receive frequency as long as the tank was oscillating. It was fun, but it was difficult to isolate the digital noise from the counter, so I only really turned on the counter as necessary, or to calibrate a dial, etc. The chassis used to be an Eico audio signal generator... In the photo the Jackson Brothers dial and bezel/tuning scale isn't completely installed. After sitting in a box for 25 years, the regen still works but probably needs new tubes, as it's rather deaf :) Blasphemy aside, I'm moving on to solid-state regens...

 

I, too, just got a Rigol DSO. Wow, the "one-button" measurement is almost too easy.
 

I'm prepping my book, Stealth Amateur Radio, for release on the Kindle (and maybe other e-book formats), but it's available now from my website, www.stealthamateur.com.
 

Keep up the good work, Bill.

I'll be listening. :)

73,

--Kirk Kleinschmidt, NT0Z
  Rochester, MN

Editor, 1990 ARRL Handbook
Technical Editor, Ham Radio for Dummies
QST Assistant Managing Editor, 1988-1994
Ham Radio Columnist since 1989 for:
   Popular Communications
   Monitoring Times and now,
   The Spectrum Monitor (www.thespectrummonitor.com)

My book, "Stealth Amateur Radio," is now available from
www.stealthamateur.com and on the Amazon Kindle (soon)

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Schematic for "Off the Shelf" Regen

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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SolderSmoke Podcast #159: Hamfests, Herring Aids, and Tuna Tins

 

SolderSmoke Podcast #159 is available.

 



http://soldersmoke.com/soldersmoke159.mp3

April 1, 2014
Vienna Wireless Hamfest
BITX Talk
W1REX speaks
Tuna Tin 2 Mojo Transfer Ceremony
After 38 years -- finishing my Herring Aid 5 receiver
Feedback, Phasing Dots, Rotational Sense, and Oscillation (or not)
Motorboating (when you don't want to)
Building my Tuna Tin 2 with parts from W1REX
On the air with Tuna Tin and Herring Aid
More Minimalist Meanderings:
An (Almost) All Altoid Crystal Radio!
Tek 465 dies (again) :-(
MAILBAG

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First Contact with Herring Aid 5 AND Tuna Tin 2

Ah, it was a good morning in the N2CQR shack!  Last week I ran into fellow ham David Cowhig at work.   I was regaling him with tales of Herring Aid and Tuna Tin derring-do.  Oh the stations I had heard with the receiver!  And the stations that I'd worked with the transmitter!   Then David asked the question: "Yea, but have you worked anybody with the receiver paired up with the transmitter?"  Uh, no.  Not yet. 

 

Well this morning I took care of that.  7040 kc.   1115 UTC.  W4ELP was calling CQ.  He wasn't too strong, and I wasn't sure if we were on the same side of zero beat (that's what happens with direct conversion -- you get all the sigs in two places on the dial) but I took a shot at it.  And he heard me! 

 

Here's the icing on the cake:  This was his SECOND QSO with my Tuna Tin 2!  Ed had been contact #4 when I was running the TT2 with the Drake 2B.   After exchanging reports he asked "Bill ARE YOU STILL ON THE TUNA TIN?" 

 

The rig (TX AND RX) is pictured above.   Close-up of the receiver appears below.  And below that is a picture of Ed, W4ELP, in his Georgia shack.  Note the HW-8.

 

Thanks Ed! Thanks David!

 



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A Short Video on my Herring Aid 5

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Herring Aid Motorboating STOPPED!

FIXED!   Following up on suggestions from Tony Fishpool and from Roy Morgan, I put a 10 ohm resistor between the two supply lines and put 100 uF caps to ground at either end of the resistor.   I can now operate the receiver at high AF gain (no problem running a speaker) without the KLUDGE of two power supplies.  The RX sounds great.    I will soon match it up with the equally awesome Tuna Tin 2 for 1976 QRP EXTRAVAGANZA. 

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Stopping the AF oscillations in the Herring Aid 5

Thanks to all who responded.   This morning I got a significant clue:  Following up on Tony Fishpool's suggestion, I separated the power supplies:  I ran the RF amp, oscillator and mixer base bias off a small 12 V battery, with the mixer collector circuit and the AF amps running of the bench 12V supply.   The AF oscillations completely stop under these conditions.  So the feedback is probably taking place via the 12 V supply lines.  73


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Direct Conversion Receivers, AF Transformers, and Motorboating

The Herring Aid 5 is a direct conversion receiver (scroll down for details).  It is a minimalist design from 1976 using parts available at Radio Shack stores.    One of the parts no longer carried by Radio Shack is a 10K-2K ohm audio transformer.  Following NORCAL's 1998 design update I ordered an equivalent Mouser part (Xicon 42TU002-RC).   I had been running the receiver with simple RC coupling instead of the transformer.

Yesterday the Mouser part arrived and I put it into the circuit.  An increase in AF gain was immediately apparent, but the thing went into AF oscillation as soon as I turned up the AF gain. 

I tried beefing up the AF decoupling.   But I think the real problem is just the presence in the middle of the board of a rather large (1 inch x 1 inch) audio transformer.    I moved it around a bit to get it away from the toroid of the preceding stage.  This helped a bit, but it still breaks into oscillation if I turn up the AF gain.

Any suggestions?  Or is this just part of  the minimalist 1976 lifestyle?  


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I Too Built a Tuna Tin 2

I didn't plan on doing this.  I didn't even really want to do this.   I've become a phone guy -- I'm not into CW anymore.  I figured I'd just finish the Herring Aid 5 receiver and settle the score from 1976 and that would be it.  But everything I read about the Herring Aid 5 included references to the iconic Tuna Tin 2.  Obviously I was also under the strong influence of my late February encounter with the original TT2 at the Vienna Wireless Winterfest.  That Mojo is powerful stuff!   Then my wife brought home this can of Russian tuna.  The dimensions were perfect.  Then I looked in my junkbox and found 40 meter CW crystals.  That was it. I had to do it. 

I built mine Manhattan style, using several of W1REX's fantastic Me-pads.   I also used as the final a transistor that Rex gave me at Winterfest. Thanks Rex.  Soul in the New Machine. 

I'm getting about 200 mW out.  I;m on 7030 kHz and 7040 kHz and 7110 kHz.   I have the TT2 up with my Drake 2-B (Herring Aid 5 integration will come later).  I can feel the Mojo. 

I just had my first contact with the TT2:  I called CQ on 7110 and AB2RA came back.  Jan was running 20 watts from an old 807 rig, listening with an old Hammarlund.  So it was HB transmitter and vintage receivers on both ends!  FB!





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Some notes on the Herring Aid 5

Sure, this receiver is not "state of the art."  But that's the whole point.  I wanted to finish the receiver project that I couldn't finish back in 1976. 

I tried to stick as close as  possible to the original design and parts.  NORCAL came up with an updated schematic in 1998 with parts that are more readily available.  But Designer Jay Rusgrove was shooting for something that could be built with all the parts coming from Radio Shack.   I think that is probably one of the factors that attracted me to the project way back when.  That's why Jay went with varactor tuning (no hard-to-get variable caps!).  And that's why he used coils that were wound  on Radio Shack 10uH RF chokes (no need for hard-to-find toroidal cores).  In this sense there is some common ground between the BITX rigs and the Herring Aid 5.

I stuck with the RF-choke as a coil idea for the VFO, but went with the NORCAL-prescribed toroids for the front end and mixer coils.  (I may go back and try to use chokes in these circuits, but I'm not sure my junk-box will yield the kind of RF chokes that Jay used).

I wish I had known a few things when I was building this back in 1976: More knowledge about how to wind the coils would have been a big help.  I wish I had realized that I could use a SW receiver to get the oscillator on the right frequency. I guess this was in the days before Ugly and Manhattan building techniques, but it would have been nice to know that there was no need to actually etch a board for this project (I did!).

The coils really are a bit tricky.  Jay didn't use any trimmer caps, so I guess you had to just hope that the front end coil and cap resonated somewhere near 40 meters.   As for tuning the oscillator, Jay recommended scrunching and un-scrunching the turns on the RF choke.  Yikes!  Give me some trimmer caps! 

I also found that you have to watch the level of the RF going from the oscillator to the mixer.   Too much, and the receiver is deaf.  Too little, same result.    You need to experiment a bit with the number of turns on the pick-up coil from the oscillator.   

The warnings about the pitfalls of that single BJT mixer were right on the mark:  Lots of AM SW breakthrough.  But I kind of like the background music.   Strong RFI from local FM broadcast stations was another story (WMZQ is a country music station!).  I reached into my junkbox and found a low-pass filter from a Heathkit DX-60.    I just put that between the antenna and the receiver and the country music was GONE! 

I really love this little receiver.  I have it playing 40 meter CW as I type.  It sounds great.   I feel the urge to built a Tuna Tin 2 and put both of them on 40. 

In the original Tuna Tin 2 article, Doug DeMaw notes that Jay Rusgrove was thinking of doing a companion receiver and says that he was thinking of calling it the "Clam Can 5" !  There were jokes about receivers for hams with "tin ears" and about there being "something fishy" about these rigs.

Thanks to Doug DeMaw and Jay Rusgrove and QST for bringing us these little circuits. 


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Herring Aid 5: Working after 38 years!

I know, it is just a little Direct Conversion receiver.  Getting it going is no great technical achievement.  But this little receiver gave me such trouble as a teenager, it has been in the back of my mind for a long time.  Finally, yesterday afternoon it started picking up signals. 

I felt a bit bad about insinuating (a few days ago -- see below) that QST may have made an error in the 1976 schematic.  They didn't.   So it was kind of spooky when I heard that first call-sign coming through the speaker:  It was W1AW!  It was as if they were saying:  "See, the schematic was correct!"

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Herring Aid: It was NOT the dots! Rotational Sense and Phasing

Opposite "sense" winding and resulting phase shift

My second attempt at building a Herring Aid 5 (the first was 1976) continues. 

I thought I had discovered an error in the schematic that (I hoped) explained my failure to get this simple receiver running (scroll down for details).  But Dex, ZL2DEX,  in New Zealand spotted something that got QST off the hook and put all the blame back on me:

I had failed to check the rotational sense of the windings.  The schematic called for 4 turns over the Radio Shack choke.  So I just went ahead and wound them.  I didn't pay any attention to the direction of the winding.  I then hooked it up in accordance with the phasing dots in the diagram.  And it didn't work.  So I switched the coil connections around.  And it worked.  Aha! I thought! QST messed up!  It wasn't my fault. 

Dex brought me back to reality.  He noted that I probably wound the coils with the wrong rotational sense.   I confirmed this.  I rewound the coil following the rotational sense of the choke.  I hooked it up following the phasing dots of the schematic.  This time the oscillator started right up.  So the problem wasn't an incorrect drawing of the phasing dots.  Instead it was my failure to remember that phasing is more than just the top or the bottom of a transformer's winding.  Rotational sense is also important.  That's why "phasing dots" are sometimes referred to as "sense dots."

This doesn't come up very often, because most of the toroidal transformers we make are bifilar or trifilar -- the windings are always in the correct sense because we twist the wires together before putting them on the coil.  When we look at those phasing dots, we are focused on getting the proper tops of coils connected to the appropriate bottoms of other windings.  We don't pay any attention to the sense of the windings.  Thanks to Dex for bringing me back to my senses :-o

Grob's Basic Electronics has this definition for those phasing dots:

"	Used on transformer windings to identify those leads having the same instantaneous polarity."

This morning I did a little experiment to confirm all this:  I took a toroidal core and wound a little transformer.  Using a dual trace scope, I looked at the input and output wave forms.  Sure enough, when the windings are in the same rotational sense, there is no phase shift.   But when that secondary is wound in the opposite sense, you get a 180 degree phase shift.  I know this is very basic, but it was fun to re-learn it and to confirm is.

But I still don't have the little receiver running.  I think there are a few problems.  That single BJT mixer stage needs a lot of RF (2.5 volts p-p) from the oscillator.   Also, I think the 10 uH chokes that I am using are not the same as the chokes used in the original Herring Aid design.  So when I build transformers on these chokes, they don't work very well.

But I will keep at it.  It has been 38 years... I can wait another week or two.   

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38 Year HB Mystery Solved? Was it the phasing dots?

 During the summer of 1976, at the age of 18, I made an audacious attempt to join the ranks of the true homebrewers.  I tried to build a receiver.  It was the Herring Aid 5 from the July 1976 issue of QST, a 40 meter Direct Conversion receiver intended for use with the famed Tuna Tin 2. As I have recounted (perhaps ad nauseum), I never got it to work.   My recent encounter with the ORIGINAL Tuna Tin 2 (Mojo was transferred to my BITX17, and it definitely works better now) got me thinking about this painful experience.   I decided to try again.

There is an updated NORCAL schematic for this rig.  I found it (and some good articles) on the NJQRP club page.   In the original, designer Jay Rusgrove, WA1LNQ, used only parts that could be found at Radio Shack stores.  In the days before the internet and Mouser, this was a good idea.  Instead of toroidal ferrite and iron powder coils,  Jay built his coils around Radio Shack solonoidal 10 uH chokes. 

The NORCAL version dispensed with the Radio Shack chokes, and used toroids.  But I wanted to try to find out what went wrong 38 years ago.  So I dug up some 10uH chokes. 

I know that my problem was that I never got the oscillator working.  I remember being able to hear signals with my "almost" receiver when I put my HT-37 in "CAL" mode and tuned through 40.  I was so close!  The Herring Aid was picking up RF from the HT-37 and using that in lieu of the LO energy that obviously wasn't coming from my Herring Aid VFO.  But WHY didn't that oscillator work?

Today I started with the VFO.   Again, it didn't work!   But now I have decades of troubleshooting experience under my belt.  So I poked around a bit.  Then I decided to look closely at the phasing.

Take a look at the schematic(above) and the picture (below).  L7 is the 10uH choke.  L6 is 4 turns wound over it (or adjacent to it).  Now, here is the key question:  Look at the phasing dots.  How would you guys connect those coils?   For me, the schematic indicates that the TOP of L6 should go to the Zener and the BOTTOM of L6 should go to the drain of the JFET.   The TOP of the choke should go over to C5, and BOTTOM of L6 should go to ground.  Right?  Or am I reading the phasing dots wrong?

Well, the oscillator was not oscillating in this configuration.  Then I did something that I might not have known to try back in 1976:  I reversed the phase of L6:  I put the top of the coil to the Drain of the JFET and the bottom of the coil to the Zener.  Bingo.  The joy of oscillation.  Now it works.  (The picture below shows it as it is when the oscillator is working well.)

So,  is there an error in that diagram?  Was this not all my fault?   

Aha! I just looked at the schematic of the NORCAL version.  Check out the dots!   I think that was the problem!

 

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