[Hallicrafters] Fw: SX100

[Carl]

Id start by zener regulating all mixer and oscillator B+ voltages. Then find 
tubes that minimize any remaining pull.

The BFO was also zenered.

It worked well enough on my MARK1B that I didnt dig any deeper.

Carl
KM1H


----- Original Message ----- 
From: "Harry Vaught, KT4AE" <kt4ae at bellsouth.net>
Cc: <Hallicrafters at mailman.qth.net>
Sent: Thursday, December 31, 2009 9:34 AM
Subject: Re: [Hallicrafters] Fw: SX100


> John,
>
> This is from a 1997 post on "Boatanchors at the Porch" by  John Sehring
> who made many informative posts on this series of Hallicrafters:
>
> "HF oscillator is pulled by signal strength on 10m.  SSB up there is
> almost impossible.  1st mixer current runs thru the HF osc. ct. (mixer
> is cathode driven) & that may be the problem, although the mixer is not
> AGC controlled & so runs Class A, constant current, or?  Don't know of a
> fix--maybe a buffer between HF osc & mixer."
>
> This is true on my SX-100 Mk.1A on 20m & up.  Too bad.  I like 15m.
>
> While I didn't have an SX-117 to go with my HT-44, I tried using the
> SX-100.  The HT-44 cal. signal would cause the pulling and it was
> impossible to have the two in sync with an incoming signal.
>
> It appears to be a feature of the series.
>
> Harry, KT4AE
> Maryville, Tennessee
>
>
> John King wrote:
>> I have just finished recapping my SX 100 and it is receiving GREAT.
>  The problem is that there is frequency pulling when the RF sensitivity
> pot is turned wide open. Movement of the pot from about 8 to 10 makes
> the oscillator pull to the extent that the frequency change  is
> extremely noticeable.
>>
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