WARNING!! I'm prolix when I use a keyboard!
I'm a pretty new ham who started as a General because I primarily
want to work QRP CW on HF. I was looking for an old rig that I could
pretty much plug 'n play on HF with a key, an antenna, an antenna
tuner and an SWR meter.
I picked up a Century/21 Model 574, serial number 574-0253, at a swap
meet yesterday in the hope of acquiring a rig that I could use for CW
QRP by just keeping the Drive control turned way down. The seller
(who wasn't the previous owner; a silent key was) said it powered up
and the digital readout presented sensible numbers, but he hadn't
checked it out further.
I opened the top and bottom covers and it looked really good inside--
no mods or repairs that I could see. The aux XTAL for 28.5 to 29.0
MHz was in the socket, and the seller had the owner's manual.
When I got it home, I turned the Drive control all the way down and
kludged an excuse for an antenna connection into the SO-259. (As a
newbie, I don't yet own a decent antenna or a single 50 ohm coax
cable with PL-259 connectors.)
When I turned it on and started listening, my first thought was that
someone had put an internal crystal calibrator into the receiver
circuit. I could hear what sounded like unmodulated carriers on all
5 bands at various points throughout the dial and could also hear a
(perhaps) 5 Hz beep at some points on the dial. I can zero-beat all
these things, but sometimes there were 2 "signals" pretty close to
each other, separated by not a lot of Hz (I don't exactly have
perfect pitch).
The idea of a crystal calibrator soon fell by the wayside because
the "signals" weren't zero-beating on multiples of 25 KHz or 100
KHz. Likewise the 5 Hz pulses weren't on any frequency that made
sense to me--for example, one place I could hear the 5 Hz was 14242
KHz or so.
I can hear real CW signals and listen to SSB QSO's, but the zero-
beatable 5 Hz beeps and things that sound like unmodulated carriers
are quite audible with no antenna connected, the antenna connector
shorted or unconnected, and the RF "Gain" control set all the way
down (CCW).
I wonder if the 5 Hz stuff is coming from the Digital Readout board.
If so, how does it show up as 5.0 - 5.5 MHz IF?
The "signals" I'm describing are not making their way from some
transmitter on the ham bands. I have 2 general coverage shorwave
portables with BFO's and don't hear these "signals" on either of my
portables; just on the Century/21. (Only 1 receiver is turned on at
a time just to make sure that one receiver isn't picking up signals
from another of my radios.)
Any ideas on how to get rid of these pseudo-signals? My first
thought, since I don't have a bench full of test equipment, is to
start replacing electrolytic capacitors all over the place since the
unit is around 25 years old. Other suggestions would be most welcome.
Tnx & 73,
Irving M. Prais
KC0QDN
tosee@ekit.com
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