[Boatanchors] Receiver drift.

[Al Klase]

Ken,

The circuit I remember involved a differential variable cap, and two 
fixed caps, one with a positive temperature coefficient, and the other 
with a negative coefficient.  Arranged like this:

                     1
< _____>
         _____   _____ DIFF
             1           1
             1           1
         _____  _____
POS _____  _____ NEG
             1           1
          GND     GND

This network would be used to replace C63, the temperature compensating 
cap, in the HQ-129.  Theory being that the total capacitance of the 
network will remain constant, for a given temperature, as you twiddle 
the differential cap to select the desired amount of compensation.

First I'd make sure the voltage regulator is working correctly, and 
Carl's suggestion of replacing some of the frequency determining caps 
probably has merit.  Prime suspects:  C9, the 6K8 grid 50pf cap, and the 
"padder" caps on the ground ends of the oscillator coils'

Don't expect miracles.

Al



On 1/16/2011 6:34 AM, Ken wrote:
> Hi Sandy&  Lists members,
>
> Many years ago, a company featured a description of a circuit for nullifying
> or minimizing drift. It was adjustable which could be set to
>
> compensate for the warmup, etc. Does anyone remember it and where I might
> find out the particulars?
>
> I am a confirmed "boatanchor enthusiast" and will allways be! My Hammarlund
> HQ-129-X has an initial warm-up drift and a very
>
> slow drift which requires resetting periodically.
>
> I have a voltage stabalizer which gives me exactly 115 vollts regardless of
> my line volltage, even if the line voltage varies from
>
> 85V to 135V. Amazing, but true. It handles everything except my Central
> Electronics 600L linear amplifier.It is a monster, came off a
>
> Navy Ship and I got it right after WW2. Now with an electric heater here in
> the shack, when the heater switches on and off, the
>
> voltlage to my radio equipment is a steady 115 volts. Best investment I've
> ever made!
>
> Take care,
>
> Ken   N5CM
>
> ----- Original Message -----
> From: "Sandy"<ebjr37 at charter.net>
> To: "Larry WA9VRH"<wa9vrh at dishmail.net>; "Eugene Hertz"
> <eugene at hertzmail.com>; "Boatanchors list"<boatanchors at mailman.qth.net>
> Sent: Saturday, January 15, 2011 8:10 PM
> Subject: Re: [Boatanchors] DO YOU REMEMBER?
>
>
>
>
>
>
> =======
> Email scanned by PC Tools - No viruses or spyware found.
> (Email Guard: 7.0.0.18, Virus/Spyware Database: 6.16700)
> http://www.pctools.com/
> =======
> ______________________________________________________________
> Boatanchors mailing list
> Home: http://mailman.qth.net/mailman/listinfo/boatanchors
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Boatanchors at mailman.qth.net
>
> List Administrator: Duane Fischer, W8DBF
> ** For Assistance: dfischer at usol.com **
>
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>    

-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/