I only wanted to mention losses because there's a growing "conventional wisdom" that you can't put up a good ham repeater without an isolator. IMHO, if you're at a sparsely populated site, and don't have anyone within a few MHz of your transmit frequency, there may be more efficient ways to fight IM.
I've often had the luxury of using sites where I was the only RF tenant, or the only one within 100 MHz. I realize that not everyone is so fortunate, and I also realize that if you're the first one to get on the air from a good site, you may one day face the choice of retrofitting with expensive anti-IM measures, or having to leave the site. Jamey, I know whereof you speak. I once helped put four ham repeaters at a site where the commercial UHF combiner system ran 3.125-inch line on the transmit side...but 1400 feet of it! 73, Paul, AE4KR ----- Original Message ----- From: Jamey Wright To: 'Repeater-Builder@yahoogroups.com' Sent: Thursday, June 05, 2008 3:05 PM Subject: RE: [Repeater-Builder] isolator - circulator loss I'd love to only have 2.5 dB loss. We're over 5 dB here on our 10 channel site but some of our freqs are 250 kHz apart too (800 MHz Trunked). 100W through the combiner and through 300 Ft of 1 5/8 cable (plus Polyphaser, jumpers, connectors, etc) yields between 15 and 20 watts (calculated) at the top of the tower. Jamey Wright Systems Analyst/EDACS Administrator Morgan County EMCD 911 Decatur, AL 256-552-0911 > Amen Paul, > > In the real commercial radio world... when working on or into > combiner systems... some people would give their first born to > have less than 2.5 dB loss per channel. > > Although the entire path to the antenna can be a lossy son of > a gun, it is the only real game in town worth playing. > > cheers, > s. > > > "Paul Plack" <[EMAIL PROTECTED]> wrote: > > > > Using an isolator between a 100-watt transmitter and a perfectly > matched antenna still only gets you 90 watts out. A typical isolator > loses 0.5 dB on the forward path. > > > > 73, > > Paul, AE4KR > > > > ------------------------------------ > > > > Yahoo! Groups Links > > >
