UHF transmission problem

miky · 16th March 2009, 12:15 PM

Yet another suggestion.

Pull it out and take it to a mate and connect his antenna to your unit.

At least this will prove if it is actually the radio that is at fault.

Treads · 16th March 2009, 12:27 PM

Originally Posted by waynep

Before sending the unit off, you probably should have the antenna checked using an SWR meter.
Using a multimeter is Ok for a basic check, but to check it properly you need a SWR meter.
The SWR meter will also test that the radio is outputting the correct "forward" power. If the "reflected" power coming back down the antenna is too high, it indicates there is something wrong with the antenna or cable. ( water inside the cable is a commmon problem - a multimeter test will probably not detect that)
Any radio shop / CB dealer should have an SWR meter. Or you may have a mate with one.

The other possibility is that you have a problem in your 12V power supply cable somewhere ( corroded connector etc ) - this will mean it works OK on the low recieve current but when you want the higher current for Tx it drops the voltage down. You can fairly easily test that using a multimeter - just measure volts at back of the the radio and compare voltage when receiving with voltage transmitting. - if it drops by more than half a volt there's a problem in your power wiring.

Waynep is on the money here, an SWR meter will give you all the info you need to know on what the unit is doing during send and receive.

JamesH · 18th March 2009, 10:28 AM

Thanks everyone. As generally suspected it was the ariel. The pin had broken off where it joins the back of the unit.

Took it to a CB specialist. He fixed this but made the general comment that my little ariel on the bullbar was not really up to convoy work and the longer distances. I told him i had an old whip ariel I found under a house which I used on trips. He asked if I knew for sure it was UHF and of course i didn't.

Anyway here is his general advice, most of you might know this but in case there are some who don't:

People tend to spend money on the UHF unit and love to use any old junk as an ariel and this is exactly the wrong way to go. Notwithstanding power, any old UHF will do as well as any other - invest the money in a decent ariel and you'll be fine and better off than somebody with the lates flash unit and a shoddy ariel.

Thread: UHF transmission problem

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Update: My UHF prob sorted and I got some ariel advice

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