Batboard

Ok, here's the deal. I'm setting up a temporary (one day) repeater system for an upcoming event this weekend. I have all my portables and repeater ready to go, but i'm contemplating a solution to the main control area for the event. I'd rather set up a temporary base station for the main control than give them a portable radio, and I have a base SM50 VHF radio that's not being used. Here's my question:

I really can't set up an external antenna for this radio, so I'm left with one option. I have numerous 90 degree angle adapters that convert a mini-uhf connector to BNC. I have programmed the radio to TX at the lowest possible output. Is it safe to use a rubber duck antenna on it with the power being so low? It basically just has to talk into the repeater that will be set up about 4 or 5 blocks away, also set to low power (about 10 watts). The radio won't be TXing much, it's more to listen to what's going on within the event, but has to have the capability to TX on occasion.

I've never tried this, I'm not sure what maximum power rubber duck antennas are designed for, I've seen some online that say you can pump about 20 watts into them with no problem. I just don't want to fry the SM50 with this.

This is an all outdoor setup too, by the way.

Set a 1/4-wave mag-mount up on the table. If its not a metal table, or there's not a metal surface nearby to stick it to, put a piece of sheet metal or aluminum foil down for a ground plane. I have used a rubber duck for a temp antenna for testing, and have seen it make the radio do all sorts of interesting things. Wouldn't be my first choice.

We were able to have a 18" whip on a SM50 at two watts, but the RF exposure limits are 7 watts at one meter. So a 1/4 wave 19" whip on a file cabinet would be best.

Ok, as stated before, this is an outside setup. Its going up on a trailer that is a stage and connected to a gas generator. I have an extra 1/4 mount mag antenna, I will definitely try to make that work, hopefully!

Your other option is leave the radio on high power and extend a dummy load on a lenght of coax away from the radio in the general direction of the repeater.

With 40 watts of output into a 100 load, I have sucessfully had many a conversation on a repeater with this setup, all be it the repeater is less than a mile away and has good Isolation and a nice front end.

I cannot say the RF exposure limits are safe as I don't have a rating sheet describing this kind of procedure and I have not yet asked my test buddy who has this info in his head as to how safe the exposure is to a test load on a radio. Considering its done way too much everyday and has not made national news yet, I wouldn't consider it much of a hazard.

If you can communicate with this setup simplex and be at both the base and repeater location with good audio, it will work. If not than you need a radiator.


CoM