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
