[ARC5] How Edwin Armstrong invented the superhet

[JAMES FALLS]

This has been such a fascinating and informative discussion! I never realized that the much lower IF was essentially a down-converter workaround for the triodes they used. Thanks, everyone! 

I have a 1933 Gilfillan 105 lowboy that belonged to a Great Uncle. it is built (If I recall correctly without the schematic handy) as a triple TRF front end with a fixed regen detector/amp feeding the AF output. You vary the volume by bleeding some of the 1st TRF output to ground. 

I don’t know if I’ll ever get it running before I stop running 😄. It was got-at a long time ago by someone who knew just enuf to really mess things up.

Jim Falls K6FWT 

> On Jan 7, 2023, at 15:57, Hubert Miller <Kargo_cult at msn.com> wrote:
> 
> 
> I don’t know the Kolster circuit but I can tell you, RCA never made any direction finding receiver that used a regenerative detector. 
> I have a pretty good stock of reference material on RCA communications products if you want to contest that.
>  
> The problem I see with the regenerative detector for direction finding is that its use requires much more attention to task, more skill.
> The regeneration level between low signal strength and maximum signal strength may need readjusting, or else there is a kind of limiting
> action, that is, nonlinear gain with signal strength, which may be a problem. This ( I think, anyway ) is a confusing factor, like using AGC
> when trying to DF. It CAN be done, but more time consuming and more likely to contain inaccuracy. It occurs to me at this moment that
> the gridleak detector, with a larger signal, will have more negative bias on the control grid, hence a kind of control against gain. Perhaps
> this is why the advice on using regen receivers for CW, when the regen is advanced just beyond the most sensitive point of operation, there
> will be a “leveling” effect on all signals.
>  
> I am thinking now of a German WW2 era receiver used for both communications and airfield DF use. I think this is the EP-2 / HE-1 receiver
> with a tuning range of something like 75 – 3700 kHz. ( I still have one to sell, which I need to pull out of storage. ) It does use a regenerative
> detector at 50 kHz IF. But as a superhet with an RF and IF stage,  the detector regeneration effect can be turned way down and the receiver
> still function as a nonregenerative circuit. The regenerative detector in the superhet receiver was something only the Germans and Japanese
> used, and even there it was not usual.
>  
> Some of you readers may have tried the regenerative IF stage trick, like on the “Command Sets” receivers. I think most people who tried this
> found it very unsatisfactory. Having one control that affects both selectivity and gain at the same time is an annoying experience. The separate
> Q-multiplier as I recall, has mostly eliminated this complication.
> -Hue Miller
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