Thanks for the input
@vagrant ,
My goal isn't so much to achieve a certain range in miles, but to be able to achieve the same reliability of communications between handhelds that we currently enjoy between the base station and handhelds. We
might currently get seven miles between the base and handhelds, but I
know we don't currently get three miles between handhelds. That said, if someone is in the camper on the base station, we can usually maintain comms for any distance family members go on foot. But if the girls go kayaking in one direction and the guys go hiking in the other, the two groups often lose comms after the first hill if there's no one back at the base station to relay.
I've got a couple of the larger antennas for the handhelds, but we don't use them all the time. Like so many things, it's a compromise. We'll use the larger antennas if the radio will be clipped to a backpack, but for kayaking with the radio clipped to a life jacket, family members can only get smacked in the face so many times before they don't want to carry a radio at all. The larger antennas seem to make more of a difference when there are only woods or buildings in the way, but in my experience, they don't help a lot in overcoming terrain. If others have had different results, please let me know.
My current "base" antenna up on the mast is really a Laird mobile antenna with an NMO ground plane kit. The claimed gain is 5 dB, and I'm assuming that's dBi, since they didn't specify. It looks like a 5/8 over 5/8 collinear.
I kind of assumed I would have to upgrade the antenna when switching from a regular base station to a repeater, but I think I'd have to stick with a mobile antenna if I permanently mounted the antenna. I'll try my current antenna lower to see if it's the height or just a more efficient antenna that's responsible for the better performance. I suspect a higher gain antenna would focus so much energy at the horizon that we wouldn't get any better performance over rough terrain, but I've got a big 8 or 10 foot base station antenna at home I could take down and try at camper-roof-height.
I say RV, but it's a trailer, not a motorhome. There are no mirrors or ladder for an easy permanent antenna mount. If we get pretty good results at the lower antenna height, and the big higher gain antennaI works better than the mobile antenna, I guess I could have the local radio shop install some sort of mount up high on one side of the RV, and just install the antenna on it instead of setting up the mast each time.
No one has asked, but I'll go ahead and mention that we almost always use low power. With the base/handheld setup, one end of the conversation is always a handheld, so it didn't make sense to pump out 50 watts. The vehicles have mobile radios, and higher power at the repeater might allow handhelds fairly close to camp to communicate with mobiles farther away, but that would be more of a bonus than a design goal.