Running your mobile radio as a cross band repeater works but can have it's quirks. My Icom IC-2720 has low audio when I use it as a cross band repeater.
You can't start transmitting until the repeater has stopped transmitting. This isn't a problem with the VE5RI repeater. However this is a big problem with repeaters which have courtesy tones installed such as VE6RJK. (Personally I feel that courtesy tones are a crutch anyhow.) This also means we should be leaving a two second pause between transmissions anyhow for higher priority traffic.
I would suggest that you put the local frequency on low power. That is if you have the VHF side listening/transmitting to VE5RI then put the UHF side on low power. 5 watts should be more than enough to go a hundred yards from your vehicle and penetrate the walls. Of course your battery will last a lot longer as most of the transmitting will be done on the UHF side.
You will also have less chance of interfering with someone else who has chosen the same UHF simplex frequency. Yes, this exercise will be in towns and villages a goodly distance apart but there's still a small chance. if we were in the same town at different sites this could be more of a problem.
I'd also suggest plugging in a smart charger. By smart charger I mean one that only charges the battery when required. If you are concerned that the charger will go missing then drive over the power cord once it's plugged in.
Test before using in an exercise.
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