[Hammarlund] Unstable Oscillator adjustments in the HQ-180

[Al Parker]

Hi folks,
    I think maybe Ed & Roy have it explained.  If it's stable at all time 
except when making an adjustment, or getting something metallic in the area, 
it's pretty normal.  Ron, you said you're using it in the CX, is it working 
OK under normal usage?  If you want to hear something squirrelly, try 
setting the osc. of an SP-600, up at 6 meters ;-)
73,
Al, W8UT


----- Original Message ----- 
From: "Roy Morgan" <k1lky68 at gmail.com>
To: <djed1 at aol.com>
Cc: <hammarlund at mailman.qth.net>; <Ron.K3PID at sbcglobal.net>
Sent: Monday, February 01, 2016 11:47 PM
Subject: Re: [Hammarlund] Unstable Oscillator adjustments in the HQ-180



On Feb 1, 2016, at 9:35 PM, djed1--- via Hammarlund 
<hammarlund at mailman.qth.net> wrote:

> I suspect what you're seeing is normal.  Remember, when you're tuning an 
> IF of 455 KHz, an adjustment of say 1 KHz is 1/455.  If you're adjusting 
> the oscillator to the same tolerance, the ratio is (at 20 MHz) 1/20,000. 
> So it is a lot harder to adjust the HF oscillator.  I definitely avoid 
> using an output meter to adjust the HF oscillator.  I either use the BFO, 
> aiming for zero beat with the generator, or I couple a frequency counter 
> to the oscillator and set it that way. And any of my Hammarlunds will 
> shift the oscillator frequency a bit when you put a metallic screwdriver 
> on the trimmer.
> Aslong as it is stable when you're done, you probably don't have a 
> problem.

I think Ed is right.

First, When tuning an IF can for peak you are dealing with a low frequency 
tuned circuit, and moving it’s resonant point around a title bit.  When you 
do the alignment on the local oscillator coil, you are dealing with a higher 
frequency oscillator and you are changing it’s frequency.  As it passes the 
point you want, it peaks the output and zips past it quickly so finding the 
peak is difficult.  Ed’s suggestion about the zero beat is good… it will be 
easier to use than a peak in the receiver output.

Second, if you are able to use a NON-metalic tuning device, your life will 
be easier.  As Ed mentions, the metal end of the timing tool changes the 
frequency of at the oscillation.  Well made chop sticks (not the split-apart 
throwaway ones) make fine tuning tools.  Just sharpen with a jack knife, or 
a file.

Roy

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