[CQ-Contest] Re: 2-Radio Interference

Tom Rauch W8JI at contesting.com
Mon Dec 25 02:02:10 EST 2000

Hi Dave,

I think you have hit the nail on the head. Has anyone here found 
any really clean radios?  

> This is not a front-end overload OR Harmonic problem.
> All synthesized radios transmit wide-band noise. The noise is
> real transmitted noise, and can be cured only by putting a filter,
> such as a stub or bandpass filter on the TRANSMITTER.

I'm facing the same thing trying to duplex on 160 meters. I need TX 
noise to be at least 80-90 dB down. 

My FT1000 is poor, most of the noise is from a dual gate MOSFET 
used in the transmitter as the  ALC controlled stage, and the rest 
is from the synthesizer.

FT-1000MP's I've tested are about the same, except on occasion 
there is a really dirty one. Some create broadband hash I can hear 
on signals coming from several hundred miles or more distant!  Of 
course if it is in the synthesizer, it appears on strong (otherwise 
clean) receive signals.

Looking at different rigs, my IC751A's and a IC781 are about 15-20 
dB quieter than my 1000D but still not quiet enough to allow me to 
get a second station into my noise floor. An old Drake T4XC totally 
quiet, as was a Ten Tec Omni 6 plus.

Stubs and filters have too little Q for close-spaced operation, but 
would work well with different band radios. I need a cheap quiet 
radio with a digital readout.

73, Tom W8JI
w8ji at contesting.com

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