You CAN hear 5 Hz tone burst. Same as slow CW. He obviously is using his
BFO and thus is hearing burst rather than a 5 Hz sinusoidal signal.
At 07:33 AM 8/21/2003 -0500, you wrote:
>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 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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