UHF white noise

Antenna cable? Ie, connections at the base and at the unit, a whisker of braid intermittently shorting the antenna input, cable damage?

If it's channel specific, could be a deeper internal fault.

Interference from other nearby equipment (or the vehicle's own systems).

Start by removing or turning off all extraneous candidates (phones, tablets, yada-yada ...) to see if that changes things.

Next, does it only happen with the engine running, or also in KOEO (Key on engine off)? Possible candidates are engine management and body management (security) systems.

Trial-and-error elimination of possible causes is the approach to use.

Moya,

Not familiar with Uniden products, does it have a knob for squelch, or just a button that you press multiple times to achieve the squelch level one requires?

Where are you taking the power source from, for the unit to work on ign? Could you borrow another aerial from someone, that you can temporarily hook up to your uhf, to see if the problem exists then?

We live close to 2 servos, <500M, and I often get constant white noise on Ch 64, when using Group Scan. Often wonder if the servos are the cause? Uhf can pick transmissions from many kms away, often hundreds of kms, which comes through with no voice, just white noise. This is when you need to increase squelch setting to stop the white noise.

Bob

I worked on a rail construction site and looked at a grader that had a uniden uhf, whenever the gps leveling unit was turned on it would wipe out the working channel.

Tried all the usual stuff mentioned here but the only fix was to fit a GME uhf that we fitted to all the new to site machines if required.

I would consider wiring it directly to your battery, with a fuse of course.

As others have said, things like aircons turning on and off and engine management systems could be culprits.

Moya

Could be something as simple as the installer being very neat and tidy, and running the RF (Antanea) lead in parallel with the vehicle's original wiring loom. This can result in induced current being picked up by the RF cable.

If this is so then simply by not being so neat and tidy, by allowing the RF lead to 'wander' all over the place and reducing any 'parallel' routing to the absolute minimum keeping at least 75mm clearence where possable, will reduce or elliminate this induced current.

Have fun, as these things can be very hard to find.
Regards
Athol

The new aerial came with a new coax cable. The old one had a tear in the sheath and thought that could have been the problem. I put the new one in conduit in the engine bay and ran it along the passenger side behind the plastic. The only lime it runs along a loom is when it goes through the firewall.

Unit is installed on drivers side up behind the bonnet pull latch with power taken somewhere there. It is off the same +wire that the caravan reverse camera is off which I don't use. Could the camera cable cause interference if not being used?

The Squelch is adjusted by the buttons on the handpiece which makes no difference to the white noise.

I might start by changing the power source to the aux battery that is in the rear of the wagon. Is it better to run twin and earth off the battery or run a single + and leave the earth onto the current location which is onto a metal part of the dash. What size wire should I use to run that length?

The only 12v thing that has been running is the kids DVD player so will play with that and see if it makes a difference. Also will try running on accessories as suggested to cancel out the engine being the cause.

Thanks for the suggestions. At least if I cancel out all of there it will point to the unit itself.

So some days the Uniden works fine, and others it gets white noise that cannot be suppressed using squelch? This suggests a strong signal from something in the vehicle. The RF is entering the CB either through the antenna coaxial lead, or through the 12V supply to the radio. Next time you get white noise, unplug the antenna coaxial lead from the radio. If the white noise stops, then the antenna lead is the culprit; conversely, if the white noise continues, it's the 12V power supply.
If the antenna coax is the problem, you need to make sure it is properly earthed at the antenna mount and (as others have suggested) not running close and parallel to 12V wiring in the car. If the white noise is still there, you'll need an RF choke fitted in the coaxial cable close to the radio. You can make one yourself (there are online tutorials explaining how to do this for a few dollars) or see if Jaycar has something off the shelf.
If the 12V supply is the problem, you could try running the radio off the auxiliary battery; however, if the auxiliary battery is wired into the car for charging purposes, the RF might still be getting in that way. In that case, try disconnecting the auxiliary battery from the car completely and running the radio whilst the car is running. Alternatively, you'll need to fit an RF choke in the 12V +ve line close to the radio; again, Jaycar should have one.