Mike, Whenever I am putting a repeater- commercial or Amateur- at a broadcasting site, my preference is to always plan for a dual 8" bandpass cavity filter between the duplexer and the receiver input. My choice is usually a Telewave TWPC-4508-2, since it is very effective and is available with a Ham discount. I have two UHF repeaters at high-RF sites (one is close to a five megawatt FAA radar, and the other is close to a 25 kW coastal radar, while both are near UHF trunked radio systems.) but the bandpass filters are effective in eliminating receiver desense caused by "brute force" RF presence. If your site has good coverage, you may not need any amplification to make up for the slight insertion loss of the bandpass filter.
I suggest that you use a good BpBr duplexer, rather than a simple notch duplexer, to gain additional bandpass filtering. 73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Mike (WM4B) Besemer Sent: Thursday, May 07, 2009 7:56 AM To: [email protected] Subject: [Repeater-Builder] 440 MHZ Duplexer Recommendation/Repeater at TV Station Greetings all, A friend of mine has been approached about accepting some tower/shack space at a local Public Broadcasting station. Between us, we've been working up our wants/needs for a 440 MHz system and I'm looking for suggestions for duplexers. The TV Station is on DT Channel 7 (175.25 video 179.75 sound) transmitting 31kW ERP. I've been fortunate so far in that both of my other sites are RF-free (we're the only tenant) so I've not had to deal with large amounts of RF floating about. What do I need to look out for? Thanks in advance, Mike WM4B
