Joel, It is not a simple task to properly apply a preamp at VHF. There's a lot of noise in the VHF band, not just from man-made sources, but also from Mother Earth and the sky. This noise pickup is often made worse when vertically polarized omnidirectional antennas are used.
Almost all manufacturers of preamps strongly recommend the installation of at least two bandpass cavity filters after the duplexer and before the preamp. The technology used in the preamp (GaAsFET or bipolar) should be based upon the site noise level, vulnerability to lightning strikes, and the presence of nearby transmitters. It can be a real challenge to increase the sensitivity of a VHF repeater, when there is a paging transmitter running more than a kilowatt just 150 kHz away! Too much gain in a VHF preamp is not always a good thing. It is sometimes necessary to add a 3 or 6 dB attenuator on the output of the preamp to avoid overloading the radio's front end. The amount of gain needed should be based upon a careful analysis of the site noise level and spectrum. I happen to prefer Angle Linear preamps, and have always had good luck with them. Chip Angle has some very informative application notes on his Web site: http://www.anglelinear.com/repeaters/repeaters.html 73, Eric Lemmon WB6FLY Joel Mele wrote: > Hello To All: Does any one have suggestions for a repeater preamp. > 160 Mhz Rcv range and 153 Mhz Xmit range. I 'd like to find a unit > with about 6-9dB gain, possibly with a preselector. I am trying to > stay away from the Adance Receiver Research type that runs "wide open" > with 24+ dB of gain. Thanks...Joel W4SLH > > > > > > > --------------------------------------------------------------- > Yahoo! Groups Links > > * To visit your group on the web, go to: > http://groups.yahoo.com/group/Repeater-Builder/ > > * To unsubscribe from this group, send an email to: > [EMAIL PROTECTED] > > * Your use of Yahoo! Groups is subject to the Yahoo! Terms of > Service. > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
