[CQ-Contest] Re: 2-Radio Interference

Tom Rauch W8JI at contesting.com
Tue Dec 26 21:19:41 EST 2000

Hi Mauri,

> When the PLL phase noise is the matter and that PLL (or a similar one) is
> used also by the receiver, not only the transmitter is guilty in
> generating a broad band (in band) noise but also the receiver can be.

In my FT-1000D, most of the noise is actually generated in the low-
level transmitter stages. It is generated mostly by a dual-gate FET 
used for ALC control.

The synthesizer seems no worse than my IC-751A.

The 1000D is almost exactly identical to a clean FT-1000MP, but 
I've seen a few MP's that have horrible synthesizer noises.    

> Who's lucky to be competent enough to deal with the PLL loop filter and
> requires very sophisticated performances by his station, like an in band
> full duplex, can try the proper modifications and enhancements to his RTX
> when not satisfyed about the factory performances. Actually, using band
> filters and unmodified IC781, 

I have a borrowed 781 here, and it is cleaner than the other radios 
but still not enough for close spaced duplex.

At 2000 feet spacing signal loss from the transmitting antenna to a 
Beverage pointed at the transmitting omni-vertical is 53.5 dB.  
Background noise floor on that antenna is about -145 dBm on a 
quiet night with 250 Hz bandwidth. I need transmitter noise to be -
80 or -90 dBm at full power, or about 120 dB below full output level.

You can see from those numbers, transmitter noise and spurious 
signals are a major concern for close-spaced duplexing if there is 
any hope to hear weak signals. My FT1000D falls about 50 dB 
short at 10 kHz spacing from the number I need.

I wonder if anyone has tested a FT-1000MP-MK V in a situation 
like this?
73, Tom W8JI
w8ji at contesting.com

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