[Boatanchors] regeneration and selectivity

[Carl]

The AC operated, ham band only SX-140 uses the same circuit. With a 1600 kHz 
IF its about useless and unstable.

Since the 140 isnt exactly a collector item I rewired that socket for a 6BE6 
mixer to 262 kHz where I had several old IF cans from tube auto radios and 
then to a proper product detector and BFO. It is now now a pretty nice 
little radio and along with an overhauled Knight T-150A it makes a compact 
80-6M AM/CW package at our summer place in Maine. Using a 455 kHz IF and 
ceramic filters from Murata or Kiwa is another option.

Carl
KM1H



----- Original Message ----- 
From: "Drew P." <drewrailleur807 at yahoo.com>
To: <boatanchors at mailman.qth.net>
Sent: Saturday, August 22, 2009 9:07 PM
Subject: [Boatanchors] regeneration and selectivity


> Henry wrote:
>
> "I brought up this idea a couple of years ago on one of the WS19 
> reflectors. About 30 years ago I added adjustable regeneration in the 
> (first?) IF stage of a TCS and a Bendix RB-(?) aircraft receiver by 
> running a high resistance rheostat between the grid and plate in series 
> with a blocking cap.
> It was very effective in both receivers, resulting in Q multiplier-like 
> selectivty."
>
>
>
> I have seen a somewhat similar scheme used in the Hallicrafters S-120 
> which
> is a minimalist general coverage receiver. The tube lineup in this unit
> is the miniature tube "All American 4" - the 35W4 being replaced by
> selenium and a power resistor. The unit's 12BA6 I.F. amplifier stage's
> suppressor grid is connected to chassis ground via a pot and nothing more. 
> The pot is the front panel control labelled "BFO".  Increasing this
> control's resistance initially provides regeneration; further advancing 
> the
> control causes the I.F. stage to oscillate, providing a BFO function of 
> sorts.
>
> Drew
>
>
>
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