Re: Frequency selection for airborne cross band repeaters
A couple of things come to mind.toggle quoted message. . .
The most important choice is the input freq as, not long after you launch, you'll be receiving any/all transmissions within hundreds of miles with no easy way to contact those making the transmissions to explain the situation and ask them to move to a different freq which means the cross-band repeater will basically become useless. Therefore I would stay away from using a repeater freq unless you are 100% sure there aren't any using your chosen input freq as either an input or output freq. For the same reason you should avoid using the simplex calling freq or any other simplex freq that some group may have chosen to use for their simplex conversations. This may be hard to determine and you'll have to simply ask around and hope for the best. Anyway, in the past we have always used a UHF simplex freq several channels away from the calling freq as UHF basically eliminated the chance of having a problem with our APRS VHF transmissions affecting the cross band receiver plus we would have much less UHF simplex activity to worry about. Therefore our cross band transmissions had to be VHF which was preferred as many more amateurs have VHF transceivers than UHF and allowed more to participate (even though simply by listening).
The output freg is not nearly as important as anyone that may be on the freq can/will simply move to a free channel. Most are quite forgiving (or should be) and after hearing a few cross band transmissions will likely realize what's going on, especially if there's a control operator, like we had, that regularly explains the situation and the input freq being used for anyone listening that may want to join in on the fun. (I believe we reached about 100,000ft and our furthest contact was from about 600 miles away. I'm pretty sure there aren't any unused VHF repeater freq's that could have been used and guessing the situation is most likely the same just about anywhere in the US.).
Barry - VE6SBS