[Boatanchors] Cheap & Easy Selectivity

[D C *Mac* Macdonald]

I suspect it is similar to what I did to my dad's

old RCA Model 10-K console radio to gain som

selectivity and also a BFO "function" to be used

as the I.F. for a Morrow 5BR-1 mobile converter.

 

It was over 50 years ago and I don't remember

the circuit, but it involved making one I.F. stage

regenerative with a potentiometer to control

the amount of regeneration.  The closer you got

to actual oscillation, the more the bandwidth

narrowed until the stage actually oscillated and

then you could receive CW.

 

As I implied above, the actual method is too far

back for my weakening brain cells to retrieve.

 

73 - Mac, K2GKK/5

(Since 30 Nov 53)

Oklahoma City, OK



 

From: gswynar at durham.net
To: hbr at mailman.qth.net; homebuilttuberadios at yahoogroups.com;

glowbugs at piobaire.mines.uidaho.edu; AmRadGear at yahoogroups.com;

boatanchors at mailman.qth.net; novice-rigs at mailman.qth.net;

antiquewirelessassociation at egroups.com
Date: Thu, 20 Aug 2009 11:13:57 -0400
Subject: [Boatanchors] Cheap & Easy Selectivity
 
Good Morning All,
 
I just ran across a sweet little article in a 1940 issue of the old

"RADIO" magazine on a fool-proof way of adding selectivity &

gain in an IF stage that (supposedly) approaches that obtainable

with a resonant crystal filter...but without the filter insertion loss,

of course.
 
 The design is rather obscure in that I've never seen anything

quite like it in any ARRL publication. Suffice it to say that it

goes a bit extra beyond the mere "...place-the-plate-lead-into-

the-IF-can" approach of achieving feedback, yet it still looks

very "do-able", and I plan to incorporate it into my 1929-style

12-tube superhet here. 


If anyone has access to any of the West Coast Handbooks of

the late 30's, you'll see the design used in the "Super/Ultra

Gainer" receiver designs described therein...
 
 Wish me luck!
 
 ~73~ Eddy VE3CUI - VE3XZ