[Collins] 75A4 CONVERSION

Carl km1h at jeremy.mv.com
Sat Jan 24 18:12:27 EST 2009


The 6GM6 only needs enough gain to overcome the mixer noise and if a 
Pullen is configured properly it shouldnt overload except under extreme 
conditions. A straight dual triode mixer isnt as robust.

With the plate and screen at 125V, and plenty of AVC action there 
shouldnt be a problem.

I modified my A4 with the 6GM6 and 7360's in both mixers in 1965 along 
with cascaded filters and AVC changes and today it still outperforms 
anything I own for pure battle condition digability on 80/160 CW DX.

If I get a K3 as planned that just may change and force me to install 
6ES8 Pullens.

Carl
KM1H



----- Original Message ----- 
From: "Mr. and Mrs. Magoo" <magoo at isp.ca>
To: <collins at mailman.qth.net>
Sent: Saturday, January 24, 2009 7:46 AM
Subject: [Collins] 75A4 CONVERSION


>I really like the 6ES8 mixer/6GM6 front end conversion I did on my 
>75A4.
> The only problem I encountered is that the RF gain is now 
> significantly
> higher resulting in overload on strong SSB signals.  I can live with 
> this by
> reducing the RF gain control but somewhere down the line I will tackle 
> this
> problem.  Apart from this, my 75A4 is an excellent performer in 
> digging weak
> ones out of the crud on CW and is sure a much more enjoyable receiver 
> to
> operate than the stock version.
>
> Bill, VE3NH
>
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