Louis wrote: > I apologize if this has been addressed previously, or even close! Do > not have a substantial amount of time to complete this research! > > Situation: An event in a remote area, one hill top is well enough > that coverage at around 10 watts VHF for the repeater could cover most > of our Aid Stations, 2 with HT's, the other 3 with Portables at 25 > watts or so, could get into the repeater! > > In the past, we have used crossband UHF in, VHF out, and it worked ok! > Except for issues with a couple of HT's not being able to cut the > input out during transmit! My goal, is to design a lite weight, low > power consumption (i.e. fewest batteries possible, as the hill top is > only assessable by hiking or horseback! > > What I have on hand: > > Single band 2m HT for receive > Single band Yaesu 2M FT2800R for transmit @ 12.5 watts! > Pair of homebrewed 2 m aluminum j-poles
Don't bother with those radios. Very poor receive isolation on the hand held (it's a made-for-ham handhled, it WILL be bad!), dirty transmitter (again, made-for-ham, it WILL be bad!) > > Basically the question is: at a 2 mhz seperation (odd split) on VHF > can one get away without using duplexers (cans), utilizing separate > rx/tx antenna's, spaced about 20 ft apart! Without desense or other > issues! BIG problems! 1) I would be very surprised if the local repeater council allowed anything other than a 600 KHZ split on 2M. I know Ohio, MI, IN, and IL would all come down on someone using other than normal repeater pairs. Yeah, ok, some would have to complain about interference first... 2)20' of separation will NOT work!!! You will need more like 60-80' vertical, or several hundred feet horizontal, to prevent desense. Since you are trying to cover a fairly wide area, you will need as much receive as you can get-EFFECTIVE receive! 3)Duplexers on VHF are very big, heavy, and very touchy! They don't like to be bounced around in a vehicle. > Being such a remote area, and the nearest 2 meter repeater is well > over 50 miles away, and nowhere near these frequencies - 145.500 > rx/147.500 out using a tone of 179.9, I do not see any interference > issues there! 145.50 is the edge of the repeater sub-band in the FCC rules. If you operate there you will have emissions that fall outside the band. 144.50-145.50, and 146.0-148.0 is the sub band, and your emissions have to fall inside that. > Observations, suggestions, and your crazy are appreciated! > > Thank You, > > K1STX The whole idea of running a portable repeater on the 2M ham is going to be problematic. I STRONGLY suggest using UHF!!!
