[Hammarlund] NOISY FRONT END TUBES

[Carl]

Well, since this isnt the Brand C forum I'll keep it short.

In 1965 I seriously modified a 75A4 with a 6GM6 RF and 7360's in both 
mixers. Also cascaded mechanical filters, hang AGC and audio changes. 
Measured 10M NF is 8dB.

I still have that radio and it shares duty on the Beverages with a highly 
modified TS-940 for DX chasing on 160/80M. It has the best in the noise 
"digability" of any radio Ive ever owned and it has helped pull out signals 
that were impossible on the 940. Its much better than my stock but rebuilt 
R-390A in that respect.

Im also interested in that Compendium info.

Carl
KM1H


----- Original Message ----- 
From: "Magoo" <magoo at isp.ca>
To: <hammarlund at mailman.qth.net>
Sent: Thursday, June 26, 2008 10:41 AM
Subject: [Hammarlund] NOISY FRONT END TUBES


> Anyone contemplating changing front end and mixer tubes in a receiver 
> would do well to have a look at the mods suggested for the 75A-4 in the 
> "Collins Compendium".  The tubes KM1H suggests are good choices; I changed 
> the 1st RF and both mixers in my 75A4 and the result was astounding.  My 
> receiver outperforms any boatanchor I have ever used.  The Compendium 
> articles give desired voltages to optimize tube operation and so the front 
> end change, at any rate, is not simply a drop-in.
>
> Bill, VE3NH
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