What is wrong with my UHF & how do I fix it?

[Cuppa]

I must admit that the idea of having to pull the uhf, (& probably the radio) out of the dash is definitely not my idea of a pleasant aftenoon’s tinkering. I hate ‘in-dash’ stuff. I may have to bite the bullet & do it myself, but if I can find anyone who knows what they are doing in my area I would be sorely tempted. A guaranteed outcome would be worth letting a few moths out of my wallet. Any recommendations for local experts Apollofish or cgm?

Re ferrites, if I do do it myself ..... can you put too many ferrites on? Don’t want to be pulling out & re-fitting multiple times.

No idea what the swr is, let alone how to check it. Re checking for a short from the coax, would I just use the continuity buzzer? Which part of the coax should have continuity to the chassis, the inner wire or the foil sheath?

[Cuppa]

The car radio has two power sources going to it, permanent power and acc power, your cb has obviously been wired to the radio permanent power line, I would change this to go straight to the battery.
It is sounding like the interference is coming in via the aerial, can you get to the back of the cb to disconnect the aerial plug?
If the interference is coming in via the antenna the only way to fix it is at the source, or possibly by moving the antenna.

You need to visit either Adelaide, Sydney or Perth to get one of us to fix it for you.

Contradicting opinions - interference via power wire or aerial - Argghhhh. I originally had the bl**dy thing powered direct from the battery & had the same issue then. I paid to get a new radio fitted & had them re-fit the UHF at the same time. Anyone wanna holiday in Ballarat???

[TPC]

You could not put to many ferrites on but I believe moving the power source to the battery will make a bigger difference.

The outer conductor on the coax will have continuity to earth and with the radio disconnected from the aerial there should be no continuity between center and outer of coax.

If it would help I would be happy to talk you through things on the phone, let me know if you want my number.

Edit-I forgot it did the same thing wired direct to the battery.

[cgm]

Sorry Cuppa, I bet there would be someone local, but I haven't needed anyone so don't know who to recommend. I'll ask around at work tomorrow incase anyone knows who could reliably do it.

[Cuppa]

You could not put to many ferrites on but I believe moving the power source to the battery will make a bigger difference.

The outer conductor on the coax will have continuity to earth and with the radio disconnected from the aerial there should be no continuity between center and outer of coax.

If it would help I would be happy to talk you through things on the phone, let me know if you want my number.

Edit-I forgot it did the same thing wired direct to the battery.

Thanks, I’ll let you know if I decide to diy & get stuck.

[BillsGU]

Too many variables. Eliminate the problems one at a time. Take the radio out and hook it up to another vehicle and see what happens. If that works then take the antenna off an try it on another vehicle. Sometimes, what seems to be the long way around is in the end the quickest.

[Agronaught]

And ultimately you could simply have a radio that isn't overly immune to noise.

[threedogs]

A SWR meter was used inline on 27mg CB radio's to test signal strength, you cut the tip of your antenna
off 1/4" at a time till the reading was correct.
How far apart are you antennas , as in radio and UHF?

[Cuppa]

Too many variables. Eliminate the problems one at a time. Take the radio out and hook it up to another vehicle and see what happens. If that works then take the antenna off an try it on another vehicle. Sometimes, what seems to be the long way around is in the end the quickest.

You are of course correct but your solution is easier said than done. I don’t have an alternative vehicle to use as a test bed. Whilst trying to avoid a pain in the arse job, it is becoming more apparent that I can’t avoid it.

How far apart are you antennas , as in radio and UHF?

UHF on the bullbar passenger side, radio just in front of windscreen pillar drivers side.

And ultimately you could simply have a radio that isn't overly immune to noise.

That is what I suspect & the idea of a whole lot of trying to sort it via a process of elimination & substitution only to confirm that would really cheese me off, but I suppose I have little choice.

Has anyone else had similar problems with one of Uniden’s ‘mini’ UHF units? My one is the UNIDEN UH7740NB.

[Agronaught]

Are you going to the australia day long weekend gathering? I can take a variety of test equipment.

To diagnose...

Run temporary power via new lines from the battery and test, you will need to disconnect the existing lines.

Rationale, interference/noise on the power supply is a big cause of issues with radios. Heck, use a small 12v SLA in the car for testing isolated from your cars power system.

If the problem is still there its probably not the power supply. If goes away we can further diagnose this issue.

Unplug the antenna and see if the problem persists.

The noise is coming via one off those two links, failing that there is an issue with the radio.