[CQ-Contest] 2-radio 'noise cancelling' ?

[Chris W Tran]

Sunday 1st November 1998

Hello all

Maybe this has been discussed before.
During the recent CQ WW Phone contest, I was on 20m SOSB
using 2 radios - with an audio switch box and 2 separate
antennas - 5ele monobander on an FT-1000MP, and a 3ele
monobander on an old IC730.

Splatter/QRM was really bad here in N.W. Europe at times
- under these conditions, with the two antennas pointing
in different directions, I noticed (several times) that I
was called by a station, who was audible with the 'stereo'
headphone selection, but was buried completely under S9
splatter ON BOTH of the other selections - i.e. the sigs.
were not audible through the QRM on either separate radio.
It seemed at times, however, as if the audio from the
station calling was 'out-of-phase' or something similar -
the audio was loud enough but difficult for your brain
to 'decode'.

Another one of our group, Stewart GM4AFF, mentions the
same effect with his 2 x TS940s set-up on 80m, with one
radio on a vertical and the other on a dipole, the 
'combined' signal seems to 'leap out at you' !
This effect is maybe similar to the old (Collins etc) Noise
Blankers which used a separate antenna to pick up noise
to allow phase cancellation ? 

Any thoughts ?

73    Chris  GM3WOJ/GM8V

<chris.tran at zetnet.co.uk>


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