[Hallicrafters] 3 IF stage Receivers

[DAN COTSIRILOS]

BTW exchanging the 6ba6 rf tube with a 6bz6 will also improve the gain on a
sx-71.  Dan
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> Greg -
> On the SX-71, Hallicrafters uses section 5-R of the bandswitch to switch
> the cathode resistance of the 6SK7 second IF amp.
> Total resistance between the cathode and the sensitivity control line is:
> Band 1     1680 ohms    (BCB)
> Band 2     1K                 (1.6-4.7Mc)
> Band 3     3700              (4.7-13.4Mc)
> Band 4     1680              (12.8-34 Mc)
> Band 5     1680               (46-56Mc)
> Why its the same, for the broadcast band and the top two bands,  I don't
> know.  Can anyone shed some light on this ?
> (Another switch, SW-2, section 1, reduces the cathode resistance on the
> first IF when the FM demod is selected.)
>
> Phil Atchley, KO6BB has suggested rebiasing the second IF stage for more
> gain. His note didn't mention whether he returns the 2nd IF cathode
> resistor to ground, as the 3rd IF does,  or to the manual sensitivity
> control line as the 1st IF stage does.
>
> 73,
> Chuck N7RHU
>


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