I would think you'd be best served by getting the duplexer ASAP. If your intent is to have a smaller, portable, quick to set up repeater... the duplexer allows you to eliminate one antenna & feedline, sets up more quickly, and works immediately without antenna jockeying, tuning, etc. (assuming your duplexer is properly tuned). I have the IC221s combo up as a UHF repeater using a mobile duplexer. Until I got the duplexer correctly tuned, the desense made the setup unusable. However, now that it's tuned I get a 15-18 mile radius coverage from the colinear ground plane 18 feet above the back of my garage rrof. It works as expected. - WB2ULR
--- In Repeater-Builder@yahoogroups.com, "Brian Rau" <[EMAIL PROTECTED]> wrote: > > I'm putting together a portable "suitcase" repeater for our search and > rescue team, using Icom F121 radios per this article: > > http://www.repeater-builder.com/icom/repeater-mod-for-icom-ic121-221-series.rtf > > I've got the two radios together and working, my question is: has > anyone had success with this configuration using two separate antennas > (no duplexer)? I've tried using two twinlead J-poles, one at the top > of a 25' mast and one at ground level (tried both RX and TX at the > top, TX at top seems to work better), I've also tried a home-built 1/4 > wave with four radials at the top (TX) with a 1/4 wave magmount on a > car directly below. I can hit the repeater with a 5W handheld from a > good long distance away, and get the squelch tail for the programmed > hang time. However, I don't get any audio repeated much farther than > a half mile to a mile away. I can do handheld-to-handheld simplex a > good deal farther than this. > > I have permission to use a 5.5 MHz split pair of frequencies in the > 150 MHz range, which is what I've done all testing on. It sure acts > like the TX is desensing the receiver. We ultimately may want to > incorporate a mobile duplexer (Sinclair or similar) into the box > anyway just to be able to use a single antenna, but I'm surprised this > isn't working better with two antennas mounted directly above/below > each other. Interestingly, Icom apparently offers this configuration > (two F121 mobiles in a Pelican case) as a standard "portable repeater" > product now, and the duplexer is an option, so I'm wondering under > what circumstances this thing will work without a duplexer? > > Any comments or suggestions are appreciated. > > Brian > K9JVA >
