UV-82 repeater

Amateur Radio
1

Trying to setup 2x UV-82’s for a temporary repeater setup. All seems to be working well except for the power supply. At first I was just using the batteries on the radios and it was fine but obviously the batteries didnt last that long.

So via the battery connections on the radio I have hooked the radios up to big 12 AGM battery via a 7.5V regulator. (Batteries are 7.4V) The radios power up and receive but wont transmit… I go back to the factory UV-82 battery and they once again transmit. Is there some funky circuitry in the battery to prevent non factory batteries from being used? Or is there something painfully obvious that I have missed…???

Thanks for the help!

2

Something painful, I think - you sure the polarity is correct?

3

I’m certian my polarity is correct. The radios both power up and both receive. Just no transmit. It’s so puzzling.

4

There’s only a few reasons a working radio won’t transmit, and the usual one is current - the voltage is sitting at just above the minimum, and when the unit tries to transmit, the voltage drops that tiny bit and transmit won’t happen, usually the display dims at this time. However, if the PSU is ok, this is unlikely. First thing would be to monitor the batter voltage at this point and see if it dips.

You mention two radios, so I assume you are powering both from the same supply? The only other thing could be if it’s the sharing of the supply line. Working on batteries, the two + and - feeds are paralleled, and maybe there is a current path that could be preventing TX? How are things connected? What are you doing to connect the audio? Could this be what is upset by the power supply communing? Drawings and photos might help.

5

Hmmm…

Well, how is it set up?
What do you use for the controller?
Do you have a duplexer?
Same band or cross band?

Are you using a single antenna or two antennas… in other words, using 2 radios and 2 antennas without a duplexer…

If so, you are getting desense. You need a VERY long separation from the transmit and receive antennas.

6

Desense - isn’t his problem, though is it? It doesn’t transmit on DC power, it does on battery power - so desense should be exactly the same. Something puts the devices into transmit = either the application of less than open circuit on the mic line, or some other switching arrangement. Hence why I suspect some form of commoning issue that is stopping the add-on device switching into transmit.

7

true the problem as described is not desense…or it would not work as he is trying to use it on battery either.

8

Howdy, FYI: you might consider getting the 12v battery eliminator for that radio. It is available from Amazon. I have one and it works wonderfully. Good luck.
Mel KM4ZVY

9

The 7.4v is nominal voltage for battery, fully charged battery is 8.4v, you have to increase voltage.