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