[Hammarlund] SP-600 alignment problems
Al Parker
anchor at ec.rr.com
Thu Jan 4 14:11:25 EST 2007
hi Bob,
Well, I'll give you the expected "reprimand" - if it had been restored
recently by someone who knew what he was doing, there would be no need for
many years for you to fudge it up.
OK, then, now - it sounds like you've got too much signal from your
sig gen, overloading the IF. Do you have it in MGC vs AVC & the RF gain
ctrl turned down? The various movements of the 455kc observed xtal freq.
could easily be caused by that. Keep the gain as low as possible.
Don't try to think that the IF freqs will determine much change the
received freq., the RF Osc. alignment (in the RF deck) does that. Moving
the 455kc IF will only change things a few hundred cycles, eg. 455 vs
454.4 = 600 cy., not the 20kc you're seeing on the BC band.
Again, "Also the audio is lousy and distorted, obviously I've knocked
it way out of alignment but can't figure out what the problem is" If
you've screwed with all the 455kc alignment that's probably the audio
problem, not the exact xtal freq. (unless you have the AVC off and the RF
gain too high).
Again - why didn't you leave well enuf alone?
I'm a grouch, but maybe that's some help in the right direction.
73,
Al, W8UT
New Bern, NC
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----- Original Message -----
From: "Bob Young" <youngbob53 at msn.com>
To: <hammarlund at mailman.qth.net>
Sent: Thursday, January 04, 2007 12:49 PM
Subject: [Hammarlund] SP-600 alignment problems
> I'm trying to align the 455 khz IF and am following the instructions in
the
> SP-600JX manual, my radio is a JX-26. The phasing control seemed a
little
> off (the nulls weren't 180 degrees apart) but the radio sounded and
> performed well otherwise. I decided to undertake alignment which seemed
> simple enough, I have a URM-25F RF generator and a HP-410B VTM so I
figured
> I had decent equipment for the job. The problem I am having is finding
the
> resonant frequency of the 455 khz crystal. The manual says to put the
> bandwidth to .2 khz and find peak output with the meter on the speaker
> output. I have the controls set the way the manual says to but the peak
> keeps moving from below to 455 to above (I've gone from 454.4 to 455.7.)
> Right now band #1 is high by 20 khz ex. WBZ 1030 is now on 1050 and all
> bands are off. Also the audio is lousy and distorted, obviously I've
knocked
> it way out of alignment but can't figure out what the problem is,
although
> I'm sure it's linked to not being able to find the correct "signal
frequency
> by the 455 kc crystal" I have gone through the whole procedure now at
least
> 5-6 times since last night, 455.35 has seemed like it was the correct
one as
> it's peaked on this frequncy several times but the dial is still off,
lousy
> audio etc. I have also set the 3.955 second conversion frequency several
> times, I'm ready to pull my hair out, does anyone have any idea why i
can't
> find this crystal frequency or other ideas of what the problem could be?
> thanks
> Incidently this radio was restored by a pro recently so obviously I
should
> have left well enough alone.
>
> Bob Young
> Millbury, Ma
>
>
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