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[TenTec] Century/21 Model 574 receiving what's not there?

To: <tentec@contesting.com>
Subject: [TenTec] Century/21 Model 574 receiving what's not there?
From: tosee@ekit.com (tosee@ekit.com)
Date: Thu Aug 21 13:01:36 2003
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 <dufferjames@hotmail.com> on Thu, 21 Aug 2003  
07:33:00 -0500: 
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 
>From: tosee@ekit.com 
>Reply-To: tentec@contesting.com 
>To: <tentec@contesting.com> 
>Subject: [TenTec] Century/21 Model 574 receiving 
what's not there? 
To: <tentec@contesting.com>
>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 
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 

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