Dayne, You are thinking along the right line about keeping your own transmitter signal out of your preamp, but please don't forget that Mother Nature is also out there, and she is generating a great deal of noise.
Chip Angle, the boss of Angle Linear preamplifiers, has written some extremely informative papers on the correct use of preamps. Here's one: http://www.anglelinear.com/repeaters/repeaters.html If your receive system is properly designed, you probably don't need a preamp. However, if you decide to add a preamp, it may be a good idea to put a bandpass cavity or two in front of the preamp, and follow the preamp with an appropriate attenuator to limit the gain to a reasonable value. One of the valuable tidbits of information on the topic is that two bandpass cavities set for 0.5 dB loss in series are almost always better than one bandpass cavity set for 1.0 dB loss. As has been mentioned many times on this list, a bandpass/bandreject duplexer (the most common type used on Amateur repeaters) has very little bandpass effect, so a true bandpass cavity in the receive chain often makes a profound difference in the operation of a receive preamplifier. A notch-only duplexer such as you describe, has essentially NO bandpass filtering, and is vulnerable to interference. 73, Eric Lemmon WB6FLY stanleyradio wrote: > > Does anyone ever consider using a preamp (ARR GaAsFET) on 440 with only a > 6-cavity notch duplexer (Celwave)? I know that this makes the receiver > susceptable to desense from other interference, but my > site is so extremely remote that my only concern is just keeping my own Tx > out. I was just wondering if for an extremely quiet site, a bandpass filter > between the notches and the preamp is worth the added > insertion loss. 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/
