1-Tube Regenerative Receiver (page 2 of 2)

One could probably use quite a variety of different triodes in this detector circuit with success.

I am including my re-draw of the original circuit with the 6C5 in place of the 6BF6.  (Click on the skizzie to the left to see it full-sized.)

I've also flipped the tube diagram right-side-up.  One could use a metal or glass tube.  I like glass because "real radios glow in the dark" :-)

I'd say that the most critical part of building the receiver is winding the coils.

If you wind your coils on plug-in coil-forms, be sure to carefully follow the convention (click on the word "convention") outlined by Mr. Morgan.  If you do, your coils will work in other regenerative receivers following the same convention.  (And who could possibly build only one regenerative receiver!)

Another note: In his text, Mr. Morgan instructs one to wind two coils, an "A" and "B" coil.

His "Coil-A" has 150 turns of grid coil windings and the “Coil-B” has 70 turns of grid coil windings.
What I found is that the 150 turns coil tunes to radio to frequencies located under the AM BC band!  I think that this band used to be used for police and ships at sea. (Maybe one of the “Elmers” can tell us!)

I was actually disappointed when I had first powered-up the radio using the "A-Coil" and did not receive many stations

But, when I wound the 70-turn "B-Coil", the stations came pouring in. A very dramatic difference to the crystal sets that I had been building!  And, you'll be able to wind additional coils for higher frequencies.

Here is a PDF chart that shows what frequencies you can expect from the pictured coils.  And the Excel Spread sheet is here:

http://www.bignick.net/Radio/images/Coils.xls

It was exciting to hear how well this humble piece of equipment can perform

You will need to develop a technique to tune this or any other regenerative receiver.

If the antenna trim is too tightly coupled, your set may not regenerate, or you’ll have dead spots in your tuning range.

Advancing the regeneration control should cause the unit to whistle or oscillate.  (If it does not, your tickler coil leads are probably reversed.)

With the regeneration turned “up”, you’ll hear a series of whistles that null whenever you tune past a station when rotating the tuning capacitor.

At that null point, you can back off the regeneration control until the whistling stops.

The set is at maximum sensitivity when the regeneration is set to just below the point at which the set oscillates.  Additionally, the regeneration control must be constantly “tweaked” as you adjust your tuning capacitor thru its range.

To demodulate ham radio Single Side Band transmissions (SSB), the technique is slightly different.

When you’ve located a SSB transmission, advance the regeneration control until the voices start to sound like Donald Duck.  Then, ever so carefully, adjust the tuning control until the “helium” voices sound natural.  (This is where a good quality vernier tuning dial, or "band-spread" helps!)  One needs to coordinate both the regeneration and tuning control to “decode” the SSB transmissions.

It takes some practice, but it’s really cool to have this radio to pull those voices out of the jibber-jabber.