[Hammarlund] Phasing control null on crystal filter for SP-600

[James A. (Andy) Moorer]

L37 is always a problem to align. It is a very broad peak at the best of 
times. The ONLY way to align it is exactly the procedure in the manual - 
including the AC voltmeter on the audio output. You have to put the 
bandwidth select to 1.4 (the most narrow non-xtal setting) and then you can 
sorta get a peak.

Another problem if you don't manage to get L37 right is that the audio on AM 
won't sound right. L37 has more bearing on the overall sound of the unit 
than any other single control. Big pain in the neck.

James A. (Andy) Moorer
www.jamminpower.com


----- Original Message ----- 
From: "Bob Young" <youngbob53 at msn.com>
To: <hammarlund at mailman.qth.net>
Sent: Saturday, December 09, 2006 2:06 AM
Subject: [Hammarlund] Phasing control null on crystal filter for SP-600


>I put a new faceplate on my SP-600 which has been recently aligned. I have 
>noticed that the nulls are not 180 degrees apart and are very broad on the 
>phasing control and I can't even align the knob with the arrow correctly 
>the nulls are so broad although I think I matched the marks on the shaft 
>pretty well. Is this something I could have perhaps done when I took it 
>apart or could it have drifted since it was aligned , it has had a lot of 
>use since it was aligned about 6 months ago (it was all gone over and 
>performs well). The null was nothing like on my HRO-60 however which is 
>razor sharp and exactly 180 degrees apart but it did get rid of the hets 
>pretty well. Does this indicate maybe I should realign it, perhaps it 
>drifted off the resonant frequency of the 455 crystal? The Hammarlund 
>manual unlike the National manual is not very clear on why you are doing 
>things, is L-37 perhaps a null adjustment? Thanks,
>
> Bob young
> Millbury, Ma
>