[amsat-bb] Re: SSB SP-7000 rejection

[WILLIAMS MICHAEL]

Tim,
 
I have a SP-7000 and get some desense, but I think this is the reason. As I key on CW, the noise floor increases depending on the position of the antennas.
 
My antennas are only eight feet above ground. I notice the desense level changes as I rotate. If the antennas are a zero elevation, I get reflections back into the 435 MHz helix antenna from nearby objects. If I point the antennas above the ground clutter, I have no desensing. 
 
This is a great preamp. I would try it without the duplexer first. By boom is about 6 ft.
 
I hope this helped. 
 
Mike (K9QHO) AMSAT  33589
 
 
 
At 05:37 AM 10/4/2008, Tim Tapio wrote:
>Hello all,
>
>I'm planning a new antenna system and planning on using an SSB preamp on the
>430 downlink side. The 7000 uses helical bandfiltering.
>My antenna separation will be on an 8' fiberglas boom. Will desense be an
>issues? Should I plan on using a bandpass filter such as a duplexer?
>
>Thanks and 73 de Tim, K4SHF