[ARC5] Receiver Filter Adaptor- From Pillar, Back to Post

[Bill Cromwell]

Hi Mike...

         ...Everybody,

There was a pooh pooh, "never again" complaint about adding a gimmick 
cap to an IF amplifier for the regenerative Q-multiplication in this 
thread. I once had and used a Star Roamer and it had that 'feature' 
designed into it's IF amp. The regeneration went all the way into 
oscillation to serve as a BFO. I was *not* impressed.

A separate Q-multiplier stage is said to be much more stable and more 
robust (Drake, Heathkit, ARRL). It isn't subjected to the same abuse as 
the 'gimmick' IF amp. I intend to find out. An oscillating Q-multiplier 
is not needed in a radio that already has a BFO. I have at least one 
spare IF can for my 80 meter and 40 meter 'command receiver' so I will 
use one of each to make the external Q-multpliers..one for each of two 
radios. Assuming I don't run out of time I'll eventually report my 
(subjective) results. There will be a 'fast' tuning problem but that 
hasn't been a severe problem - yet. I don't expect to reduce the 
bandwidth to 75 cps! Maybe I can find an overdrive transmission from a 
Nash Rambler to slow the tuning a little - mounting it on the front of 
the radio. Or maybe mounting the radio on the back of the transmission. 
-evil grin-

73,

Bill  KU8H


On 02/18/2016 08:20 PM, Mike Everette via ARC5 wrote:
> Hi Bruce et al,
>
> I agree with you in principle.  My position, though, is to keep things 
> more or less technological-period compatible.
>
> An example... back in high school (early-Renaissance days) I built a 
> wide-open bread-board (actually, wood from a "Producto de Argentina" 
> corned-beef box, and an aluminum-foil-lined piece of Pratt & Whitney 
> Aircraft engine-gasket Masonite box for a panel) version of the 
> "Regenerative Single-Signal Superhet" from a 1943 ARRL Handbook that 
> had been one of my dad's WW2 Army Signal Corps School texts (original 
> article is in November 1940 QST, see the archive on the ARRL site). 
>  The design was by George Grammer, one of the best ever, who edited 
> the Handbook from sometime in the 30s until the 1970 edition (and 
> after he left, the dumbing-down of the Handbook commenced, IMHO).
>
> I used salvaged compression-trimmer tuned IF cans from an old 
> acey-deucey radio instead of the article's highly-recommended Millen 
> iron-core types.  (The object was to use "junque" parts throughout; 
> this was a skool-project.)  So, the passband was far from ideal, maybe 
> 20 KHz wide (curve plotted using a BC-221 and a VTVM), which made 40 
> meters kind of tough in those Radio Moscow days.  BUT!  Put that IF 
> into regeneration, per Grammer's original brilliant design,
>
> and....
>
> The improvement was nothing short of dramatic!  Even with the BeeCee 
> IF cans.
>
> There was a thread about employing IF regeneration in Command 
> receivers in the not too distant past... it's well worth trying this; 
> aka the KISS method ("by George )!.
>
> By the way, I still have my breadboard receiver, and it still works.
>
> 73
>
> Mike
>
> WA4DLF
>
>