[Boatanchors] Cheap & Easy Selectivity

[Jack Taylor]

Seems I recall a similar mod  to improve selectivity on the
ARC-5 series of receivers.  pieces of wire twisted
together across the IF stage.

Jack - N7OO

----- Original Message ----- 
From: "Carl" <km1h at jeremy.mv.com>
To: "Ian Wilson" <ianmwilson73 at gmail.com>; "Boatanchors" 
<boatanchors at mailman.qth.net>
Sent: Thursday, August 20, 2009 10:43 AM
Subject: Re: [Boatanchors] Cheap & Easy Selectivity


> Sounds a bit like the 8 tube super in the first edition 1942 ARRL HB and
> possibly earlier.
>
> Carl
> KM1H
>
> ----- Original Message ----- 
> From: "Ian Wilson" <ianmwilson73 at gmail.com>
> To: "Boatanchors" <boatanchors at mailman.qth.net>
> Sent: Thursday, August 20, 2009 11:55 AM
> Subject: Re: [Boatanchors] Cheap & Easy Selectivity
>
>
>> Ed, thanks for pointing this out. I'd noticed the Super-Gainer before in
>> the
>> early Radio Handbooks, but had never really studied it.
>>
>> The lineup is like this:
>>  - pentode RF amplifier/mixer with regeneration to improve
>> gain/selectivity
>>  - triode heterodyne oscillator
>>  - 456kc IF transformer
>>  - triode detector with cathode regeneration
>>  - triode audio amplifier stage
>>
>> Regeneration in the RF amplifier is by feedback from the cathode to a tap
>> on
>> the coil (like a Hartley oscillator). The level is controlled by
>> varying the screen
>> voltage. LO injection is to the suppressor grid of the pentode.
>>
>> Regeneration in the detector stage is obtained by lifting the bottom end
>> of the
>> secondary of the IFT (connected to the detector cathode by a bypassed
>> resistor)
>> from RF ground. This is done with a potentiometer with an RFC across it.
>>
>> This is a pretty nice design, with the regenerative detector being
>> isolated from the
>> antenna.
>>
>> 73, ian K3IMW
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