Why do you feel the need for a preamp? Also, to check for desense, you need everything operational. Get someone with a very weak signal to transmit while you disable the repeater transmitter. If there is no change in noise on the repeater's local speaker, you are OK. If the signal gets quieter, then you have desense.
Oh, and the transmit and receive audio lines to the controller should be individually shielded, not just an overall shield around a bundle of wires. Chuck WB2EDV ----- Original Message ----- From: "Bob Ricci" <b...@af6d.com> To: <Repeater-Builder@yahoogroups.com> Sent: Thursday, February 05, 2009 5:04 PM Subject: [Repeater-Builder] Re: Hamtronics Helical Resonator Preamp orAdvanced Research Preamp > Thank you all for some excellent advice for a first-time repeater > builder. I have decided to move the antenna to the other side of the > house and push it up 60 feet. My home sits about ~15 feet below the > road, so this will give me a net gain of ~45 feet. I'll feed it with > hard line and do it right. This will get the repeater antenna away > from my own stuff in the shack. The repeater will actually go into a > cinder block walled room > > The Vertex VX-4100's are solid radios encased in aluminum. The > plastic on the outside is decorative. Using the repeater right next > door to me and a hand-held without an antenna and 1/8th of a watt, I > generated a signal and then kerchunked the repeater next door. No > desense or white noise. I'll check this with a service monitor when > it gets back up here, but this test was positive and without the > cavities inline. > > I will use quality DB15 shielded computer cables to soldered DB9's on > the RC210 controller. >
