[Boatanchors] National SW-54 "CWO-IF AMP"

Fuqua, Bill L wlfuqu00 at uky.edu
Tue Oct 18 00:00:22 EDT 2011

I used to mess with the feedback control on the back of my S38E to stop the oscillation of the IF and use it as a Q multiplier.
Mine had provided feedback by ungrounding the suppressor grid which then was grounded thru a variable resistor on the
back of the chassis. You could adjust it as you would a Q multiplier. Just could not have CW and selectivity at the same time.
But with a BFO you could have both.

From: boatanchors-bounces at puck.nether.net [boatanchors-bounces at puck.nether.net] On Behalf Of Steve Mulder [smulder3 at cox.net]
Sent: Monday, October 17, 2011 12:13 PM
To: Boatanchors at puck.nether.net
Subject: Re: [Boatanchors] National SW-54 "CWO-IF AMP"

I would like to thank everyone who replied offline to my question about
the "CWO-IF AMP". I understand how it works now. A number of people
pointed out that a similar circuit was used in the Hallicrafters S-38
series of receivers, and that this type of circuit was inferior to a
'real' BFO.

In some further reading on this topic, I came across a website that
showed how to add a tiny BFO to an S-38:

Thanks for all the help.

Steve Mulder

On 10/16/2011 10:22 AM, Steve Mulder wrote:
> I read that the National SW-54 does not have a BFO, but it does have a
> "CWO-IF AMP". Could someone here give me a brief explanation of how a
> CWO-IF AMP results in an audio tone for CW signals?
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