Batboard

Just finished an install in one of our engines -- one 6500 (VHF) and one 8500 (VHF/UHF). Tested the 8500 on a repeated channel, worked well. Then I tested the 6500 and couldn't hit the repeater. It receives fine but on transmit, nothing. On a direct channel, rx/tx worked fine. The issue was just on repeated channels.

Someone else did the antenna install, so I opened everything back up and the antenna seemed solid. The connection to the brick (remote mount) was solid. I then tested it against a really close repeater and it worked fine. I went to one of our other rigs that recently had the same set of radios installed and noticed the same thing. Inside the apparatus bay, the 6500 can't hit the repeater, but the 8500 hits it just fine.

They're both transmitting on high at 55w for VHF. Is there a known reason why the 8500 has a better VHF range than the 6500? I know it has the massive black antenna, but I wouldn't think that would make the big difference -- I could be wrong though.

Thanks for any input anyone can provide!

No, unless there's something wrong two radios in the same band with the same output power and similar gain antennas should perform pretty much the same. Make sure you're comparing apples to apples, both radios on the same channel, not one VHF and one UHF. Simplex to a nearby radio is almost always going to work, it's not much of a test.

"Seemed solid" is not a measure of an antenna system's performance. Unless someone really screwed up the install a visual inspection is generally useless, for example a connector can look perfectly normal but still be shorted. The antenna system should be tested with a watt-meter for correct forward and reflected power levels and the cables checked for short/open circuits. That should have been done as part of the install, if not, get a better installer next time.

You should also not test from inside the apparatus bay, pull the trucks outside away from the building, antenna type and mounting location can cause a big difference and something in the bay may effect the antenna on one radio more than the other. Moving a vehicle 10 ft. can make the difference between hitting a repeater or not. The APX-8500 will have a different antenna since it's a dual band radio.

Thanks for the reply. Ya, it's apples to apples. Both radios on the same channel...transmitting on one is heard by the other but not the other way around. It's got to be an antenna issue, that's where I'll keep troubleshooting.

not sure what mode that channel is in ....P25 , EM narrow or FM wide.

If P25 it may be your alignment