Bob, Which preamp you use to work properly in your situation depends on several details.
We need a lot more information from you to make any firm recommendations. There are cases where a lower gain preamp will actually produce more measurable results. If for example the site has a higher than normal noise floor a lower gain preamp will often times amplify more of the signal and less of the extra site noise, where a higher gain preamp may amplify both the noise and signal, giving you a signal with more noise than you would like. The choice of preamp also depends on what equipment you are using and what the power level of the transmitter is, and what type of cabling is used for intercabling within the repeater, and also what type of feedline to the antenna you are using. In general on a site with a high noise level I prefer to use Angle Linear preamps, or if you are using a Micor or Mastr II repeaters, the factory preamps can be a help as they are only about 10 db gain. As was mentioned, a pass cavity (the deeper the skirts the better), after the duplexer in front of the preamp, is a must, especially on a noisy site. If you can give us a little more information, some of us can get you a little closer to where you want to be. >From my past experience with them, I would not use a Ham-Tronics preamp on a noisy commercial site. Joe - WA7JAW Repeater-Builder@yahoogroups.com, "Bob Ricci" <b...@...> wrote: > > Hamtronics has a preamp with a helical resonator with a 18dB preamp. I > am at a high elevation with noise all around me. Advanced R3esearch has > a 24dB preamp with a low NF and 1dB compression point. Either would be > behind a WACOM 642 6 cavity duplxer. > > Which would be the better approach? The ultimate goal is to improve > reception of handhelds in a mountainous region. >
