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
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
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
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