Just to follow up and "close the loop" on this thread, I got a Sinclair MR256 mobile duplexer, threw together a quick test setup and tested it on my drive to work this morning... it's kicking butt compared to what it used to do using two separate antennas. I'm now getting good audio from five miles away using a 5W handheld, and no real effort to optimize repeater site location (i.e. it's in my backyard). Thanks for the input, folks...
Brian K9JVA --- In [email protected], "covertp9" <[EMAIL PROTECTED]> wrote: > > 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 [email protected], "Brian Rau" <brau@> 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 > > >
