U.H.F radio,voice breaking up and interferance at high rev's

don't have an answer but I'll watch with interest.

I have an 04 GU 3lt with the same problem, clear Rx and Tx with the motor off, but as soon as I start the motor the 'interferance' (actually just like the radio is a bit deaf or I am speaking very quietly) begins. My cables are good and straight to the (2nd) battery and I have already rerun the aerial cable away from the electronics under the bonnet.

So as I said, I'll watch with interest

No expert, but the direct wiring to the battery sounds good. All professional installers use this method.

If you think about it, the wire running from the battery (or fuse box) is there only to power the stereo/cd player/speakers. Transmiting on a radio would requires a bit more power as I understand than receiving. Also, the stereo would have some sort of interference reducer (I'm sure there's a tecnical name for it!) either in the power line, or internally. These are usually needed because of interference from the engine. At a guess, using not heavy enough wire guage, or sharing it with something else, along with no interference reducer, could lead to these problems. I would do the direct wiring to the battery, both positive and negative, and an expert may correct me, but twisting the negative around the positive all the way to the radio may aid in reducing interference.

I base none of these above theories on anything I've ever learnt, jsut on a few things I've seen and heard. If I'm wrong, I will stand corrected. It's just that no-one had replied yet!

D-Jack

Put the power straight onto the battery that's what I did and I have no dramas

Worn alternator brushes.

never, Never, NEVER connect the negative of a UHF (or any device) directly to the battery. You should connect them to the chassis, if you want close to the battery, but never directly to the battery!!
Imagine this scenario... You run the nice thin wires that connect the UHF to power through your dash, firewall and engine bay and connect them directly to the battery terminals. Things work fine for a while, and for many this is great and they will experience no problems. Then one day, thousands of K's down the track, the main earth lead that connects the engine block to the negative terminal fails. Over time vibration caused by the engines operation can cause the fine copper wires inside the cable to break. Suddenly when you go to crank the engine over, the only path the starter motor has to ground is through your UHF (antenna is grounded and the set is connected to the negative terminal) or any other device you have connected directly to the battery. Imagine 100+ amps being drawn through that little wire.
Instant fire!! The ONLY device that can have an excuse to connect directly to a battery is a winch (due to the incredible current draw when running).

As far as GREENDOG's interference problem, is it the engine/alternator OR is the interference just general noise in the cab caused with high revs?
Another thing that can affect the operation of UHF's during transmit is something called microphonics. This is where vibration in the car is transfered directly to components inside the radio and then transmitted. This is more common that you might realise. I repair UHF's (and other two-way radios) as part of my job and I see it quite often. A cure can be simple or quite tricky. This is the purpose of the wax inside the little shield box in some of the older Uniden UHF radios. Those that mount their UHF on the dash and get them too hot might have seen wax on the edges of the lid. The wax is supposed to hold critical components from vibrating, causing microphonics. It melts when the radio is cooking on the dash and runs out (the main board is upside down in many UHF's).

It could be a faulty regulater in the alternater even though its new try dis connecting the main battery supply to the alt and running it then and seeing if you get the interference if you do try fitting a noise suppersor to the alt no the uhf fix the problem at the source.

Thanks to every one that helped find the problem,it ended up being a faulty antenna in the end so just out of warranty 110 bucks later sounds alot better,cheer's GREENDOG