Sorry I failed to make clear that a *tone* I could hear was going on
and off at 5 Hz. In addition to being able to hear what sounded like
unmodulated carriers at different frequencies that I could tune to
and zero beat, I could also zero beat (at different frequencies on
all 5 bands) an internally generated signal that was a steady beep-
beep-beep at 5 Hz. Sort of like 5 dits per second and the frequency
of each individual dit depended on where I was tuned, making it
possible to zero-beat this pseudo-signal.
Quoting James Duffer <firstname.lastname@example.org> on Thu, 21 Aug 2003
Are you sure you are hearing 5 Hz.......? How did
you determine it was 5
Hz... That is an extremely low frequency that one
could feel but
hear....maybe with that low of frequency response in
your hearing you will
be noticing more noises than the average bear.
Good luck with the rig, I have a Century 21 that I
got at a hamfest, that I
have never used except for an initial turn on. It
was extremely sensitive
to the amount of drive, just a twitch on the drive
control could result into
much output and shutdown. I also bought one from
this reflector or maybe
the forsale swap reflector that was a basket case,
it was the one with a
digital readout. The power supply had missing
components including the
large filter cap.
73, Jim, wd4air
>Subject: [TenTec] Century/21 Model 574 receiving
what's not there?
>Date: Tue, 19 Aug 2003 17:38:00 +0000
>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
>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
>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
>The idea of a crystal calibrator soon fell by the
>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
>are quite audible with no antenna connected, the
>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
>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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