|[AMRadio] Crystal Filter adjustment procedures|
ranchorobbo at gmail.com
Sat Mar 29 20:01:01 EDT 2014
I tried Eric's procedure on my CR88. It didn't work out exactly the
way I expected, but I wrote it off to the variety of vintage
receivers, and the possibility that RCA did things a bit differently
with the AR88 series. I planned to try it again on my 75A-3 but have
not gotten around to it yet. Eric used a SX25 as one of his receivers
as I recall.
It is important to point out that he refers readers to their receiver
manual first. He also writes that his procedure will work with
_nearly_ any "XTAL PHASING equipped radio" emphasis on "nearly."
The first thing not completely clear to some people is the part about
centering the BFO: "Rotate the BFO through its range. The pitch of
the noise at either extreme should be the same." I bet "range" is
interpreted as 180 degrees (90 degrees each side off center top) by
some and 360 degrees by others.
He starts out having readers tune to a broadcast station but ends up
with a CW audio note. Somewhere along the way there is a transition
from one to the other but it isn't clear. The end of the section
seems to involve tuning and the BFO and nothing about the xtal phasing
control. I think part of my problem is that the section seemed to be
written for receivers with band spread but a ham band only rx or any
gen.gov. with just one tuning control ought to be the same.
I probably rushed through it in the evening when I was tired and in a
hurry and it is something that I have to think about first.
I criticize QST quite often but I also make compliments when the
occasion warrants it and I give credit to QST for publishing something
about vintage gear. At least they are trying. With K2TQN no longer
writing the vintage radio column, they had a guest column, or
temporary fill-in column about the DX60. I hope they keep it going.
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