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The tranceivers I upgrade myself with 10W (70cm) and 20W (2m) modules, and 
we used an self-made arrow-a-like antenna.

However there are some situations to take care. These are when the receiver 
is in de direct RF radiation field of the antenna. (Its also not save for 
yourself). Or in close rainge (<3m) when using 10W or more. For my backpack 
station I used 4m coaxial cable, and stayed always behind the reflector of 
the yagi and this gave never problems.

To have a look of my backpack station, look at my webpage, under "Portable 
Satellite Station" or "Europe Satellite DX-Expedition report after"

Something what might be te problem is a mixing product with some other 
broadcast signal.
I had this with Ao10, when I made an uplink signal I could hear myself with 
a TV audio signal on the downlink. After some search I find out that the 
cable TV was more RF TV.
An TV signal on 581MHz mixed with my 435.1MHz uplink caused together on my 
mast pre-amp input (581 - 435.1=) 145.9MHz signal.

I made a 1/4 wave notch on the 581MHz at the input of the pre-amp, and the 
problem was over.
Propable you have also some problem like this.

73 de PE1RAH,
William Leijenaar

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