[ARC5] FW: RE: How Edwin Armstrong invented the superhet

[howard holden]

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From: howard holden<mailto:holden7471 at msn.com>
Sent: Sunday, January 8, 2023 11:10 AM
To: William Cromwell<mailto:wrcromwell at gmail.com>
Subject: RE: [ARC5] How Edwin Armstrong invented the superhet

The Hallicrafters S-120 (and WR-600) also used the regen IF. I used one down in Guantanamo Bay as KG4DF for a year back in 67-68. Worked mostly 10 15 and 20, both CW and AM. Had a ball. Yes the BFO done this way is kinda ratty but with decently trained ears it’s certainly doable and fun.

73, Howie WB2AWQ

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From: William Cromwell<mailto:wrcromwell at gmail.com>
Sent: Sunday, January 8, 2023 10:38 AM
To: arc5 at mailman.qth.net<mailto:arc5 at mailman.qth.net>
Subject: Re: [ARC5] How Edwin Armstrong invented the superhet

Hi,

The Knight Star Roamer used the regenerative IF trick primarily to serve
as the BFO. It was controlled from the front panel and it did affect the
bandwidth and rf gain. It was not very satisfactory but was *cheap*. I
used one for a couple of years.

73,

Bill KU8H

bark less - wag more

On 1/8/23 02:33, 1oldlens1 wrote:
> A comment. A regeneration has two advantages for CW: the first is that
> as it approaches oscillation it becomes narrower in selectivity.  When
> it begins to oscillate the oscillation acts as a BFO
>   There is a critical adjustment just at the point of oscillation
> where the bandwidth is minimum
>    More feedback will begin to broaden it out more.   At minimum
> feedback the gain is minimum and bandwidth maximum.  Note that the
> change in gain and bandwidth is confined to the regenerative stage.
> Pre selector stages are nor affected.  I don't remember the theory but
> the change in gain with feedback is probably not linear.  In any case
> old RDF sets are likely TRF. I believe I have schematics for both
> Kolster and Radiomarine RDF receivers in some very old books.  The
> main thing is to be able to here the variation in signal strength as
> the antenna is rotated. Precision measurement is not necessary, only
> thr relative variation with direction.  Actually only the null is of
> interest.
>    There were schemes of adding regeneration to an IF stage to make it
> narrower and to make it oscillate so as to act as a BFO .  The
> relatively crude circuit used in the S-38B and later,and SW-54 are
> examples.  This arrangement is strictly an economy.  The original S-38
> has one more tube than the later versions.
>
>
>
> Sent from my Galaxy
>
>
>
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