Testing UHF Radios

Submitted: Thursday, Oct 31, 2002 at 01:00
ThreadID: 2262 Views:10629 Replies:9 FollowUps:7
This Thread has been Archived
I have a Uniden UH-090 Dual Band CB that gets pitiful reception/transmission.

I've had the unit for 12mths but never/rarely used it. On the weekend I went out with a 4WD club for the first time and the radio was next to useless. I Could only receive 1 persons out of 9 transmission clearly. I borrowed a handheld GME Unit and it was brilliant - crystal clear.

Is this an aerial, cable or radio issue? Where do I start?

I'm on the Sunshine Coast QLD. Are there any CB test places or who does this type of work

Thanks
Greg
Back Expand Un-Read 0 Moderator

Reply By: ExplorOz Team - David - Thursday, Oct 31, 2002 at 01:00

Thursday, Oct 31, 2002 at 01:00
Greg,

I would start with the aerial cable and the connections on the antenna base. As this usually a fitting on the bullbar it is exposed to weather and damage can occur from passing trees or kids or a number of reasons. Check that the connections are solid and that the earth lead is well connected. If it is an enclosed sprung base or you are unsure if the connections are ok, then my advice would be to disconnect the aerial ie. unscrew it, then remove the cable from the back of the radio and using a mulitmeter and long lead check for continuity (ie a 0 Ohm reading on multimeter). Firstly check there is NO short (not 0 Ohms) from the center pin to the screw fitting, then check that there is a short from the screw fitting at the radio to the aerial base and a short from the centre pin at the radio to the centre connection on the aerial.

Failing this make sure the black (earth) wire on the radio is connected to the chassis or battery - post correctly.

These tests you should be able to do yourself (if you have a multimeter of course - If you do not Dick Smith sell them very cheaply). If this fails to resolve the issue then it is a matter of checking all other cabling and connections are 100% and maybe reterminating them all. If it cannot be found in the cabling or connections, then try a different aerial. If all this fails the radio is most likley to be faulty.

I would put my bet on the aerial cable firstly however.

Hope this helps
David
AnswerID: 8054

Follow Up By: Greg - Qld - Thursday, Oct 31, 2002 at 01:00

Thursday, Oct 31, 2002 at 01:00
Thanks for that David,

I've been looking for an excuse to buy a Multimeter for a while. Now I can justify it to "The Boss" (read wife).

I pulled the aerial cable right out to check for kinks, damage etc

No visible damage with cable. I tested as you suggested and all seems OK. Next is time for a new aerial I guess.

Thanks
Greg
0
FollowupID: 3804

Reply By: Truckster - Thursday, Oct 31, 2002 at 01:00

Thursday, Oct 31, 2002 at 01:00
I too would check the ariel cable.. I had this problem with mine, it had gotten water into it, and was cactus.

But since you havent used it for ages, check the ariel cable to the radio, could have worked itself loose...

If your unsure, take it to any CB Communications place, they will help you out.
AnswerID: 8058

Reply By: Member - Nigel - Thursday, Oct 31, 2002 at 01:00

Thursday, Oct 31, 2002 at 01:00
If you bought the Uniden from somewhere other than a radio tech then it most likely has never been tuned properly. May be worth spending $30 or so to get it into proper spec (they have poor quality control in the factory) once you've sorted the likely antenna and/or cable problems.

Or sell it to some unsuspecting soul and buy a GME :)
AnswerID: 8062

Follow Up By: Stephen - Sunday, Nov 03, 2002 at 01:00

Sunday, Nov 03, 2002 at 01:00
All aerials need to be tuned to the "surrounding factors". Bullbar, size of bonnet, shape of vehicle.
The best answer to this type of question (as with most 4wd related questions) is consult a specialist. Greg ultimately did that and problem was solved easily.
It is very easy to "cook" the transmitter of a radio by having a mismatched or short circuit antenna connection.
Uniden make some fine products and as Peter replied - they would be out of business if their quality was not excellent

Stephen Hartley
Brisbane
0
FollowupID: 3845

Follow Up By: Member - Nigel - Sunday, Nov 03, 2002 at 01:00

Sunday, Nov 03, 2002 at 01:00
Aha - so let me get this straight...

Uniden's need to be tuned to their environment to be able to achieve the claimed output of 5 watts (as Peter has admitted to)

GME's put out 5 watts straight from the box.

I guess if I was making money out of tuning Uniden's then I'd recommend them too.
0
FollowupID: 3846

Follow Up By: Member - Nigel - Sunday, Nov 03, 2002 at 01:00

Sunday, Nov 03, 2002 at 01:00
Stephen, if you read Greg's conclusion properly, he says it was the radio, not the antenna that needed tuning. I stand by my statement that all Uniden's should be tuned by a tech, as they aren't reliably tuned properly in the factory.
0
FollowupID: 3847

Reply By: ken d - Thursday, Oct 31, 2002 at 01:00

Thursday, Oct 31, 2002 at 01:00
Hi Greg.- A few tips. Turn of the squelch, ie to where it gets noisey. Not much noise means not much coming in and is usually feeder or antenna. If you haven't got a meter a torch battery and globe will help. Disconnect the cable and antenna. Conect one side of the battery to the outside of the cable and the other to the inner. Then do the same with the globe on the other end. If the globe doesn't glow the cable is buggered. The antenna is a similar setup. A whip antenna has a piece of wire wound up under the sheath to the end. This sometimes breaks. If it has a metal tip good, otherwise strip back a little plastic at the tip. ( You can repair it later with araldite). It sould be zero ohms from the base to the tip. A meter is easier but you can make a circuit with the battery and globe. Connect one side of the battery to the base and one side of the globe to the tip. Now use a piece of wire to connect the other side of the battery to the other side of the globe and if the the antenna is OK the globe will glow. - It will work but, get "The Boss" to help hold the globe etc, and after all the farting around she will beg you to buy a Multimeter, hence killing 2 birds with one stone. - Cheers Ken
AnswerID: 8067

Reply By: Bob Y. - Thursday, Oct 31, 2002 at 01:00

Thursday, Oct 31, 2002 at 01:00
Greg, I'd endorse both David and Truckster's comments. Check the coax and the fittings. We have just purchased a Cat grader, 2nd hand, and got a GME TX4400 and radio/cassette fitted by a tech, cost $300. On arrival the GME wouldn't reach our repeater 30 k's away. Unscrewed the plug off rear of UHF, and there was a short in coax, removed plug, checked coax again. No problem now, refitted plug, checked before soldering. Now reach repeater when 50 k away, albeit somewhat scratchy. Have also seen perfect looking coax, running through engine bay, that couldn't transmit a decent signal, being fed by a 100 watt Codan. Coax is cheap, replace it, check plugs, and follow Davis advice on aerial. Even a Uniden can transmit a strong signal, with right gear ....
AnswerID: 8069

Reply By: Peter - Thursday, Oct 31, 2002 at 01:00

Thursday, Oct 31, 2002 at 01:00
Greg,
We didn't ask you if you were handy or not.
Nor did we ask if you purchased the radio from the Uniden outlet.
If you did, and if you have exhausted all avenues except for the radio, contact Uniden for assistance.
If you have a fair idea of what you're doing and am confident in doing the job properly, have a browse of the web to see how to set up coaxial cable and connections, PROPERLY.
If you're not real sure how to do it, go to your local car audio shop where they supply and fit CB's and the like.
They will do the job for you and it will be done properly.
You can ask them to check the radio for output, too. They should have the equipment.
If you go to a dedicated Communications Shop (which is the best option) you can have them tune the radio properly and ensure the power output is at its peak, before any distortion occurs.
I know about that as I used to do it to every unit before it was sold.
Contrary to what I read in another reply, the quality control is not poor. It is of a very high standard. If it was poor then Uniden would be out of business.
Do not scrimp on quality either. Get the job done by a professional and you can be assured the job will be done right.
AnswerID: 8082

Follow Up By: Member - Nigel - Sunday, Nov 03, 2002 at 01:00

Sunday, Nov 03, 2002 at 01:00
So how would you explain a brand new Uniden only outputing 2.5 watts into a dummy load of the correct impedance?

Sounds like poor quality control to me. All Unidens should be tuned by a tech before being sold. You have even said that you did this yourself. Would that have been necessary if they were tuned properly at the factory?
0
FollowupID: 3842

Reply By: dave - Friday, Nov 01, 2002 at 01:00

Friday, Nov 01, 2002 at 01:00
I'll endorse the above comments, check the coax and the connections.

Also, this may be a silly suggestion and don't mean to insult your intelligence BUT, seeing as its a dual band radio, did you connect the correct aerial to the correct plug, just a thought.

And if all else fails, buy a GME.

Dave
AnswerID: 8089

Reply By: Member - Steve - Friday, Nov 01, 2002 at 01:00

Friday, Nov 01, 2002 at 01:00
Tandy have a great little multi meter for 25 Bucks. "DIGITOR Q1467". works well at low ohms

Steve
AnswerID: 8095

Follow Up By: Greg - Qld - Friday, Nov 01, 2002 at 01:00

Friday, Nov 01, 2002 at 01:00
Thanks Everyone,

I did as all suggested. It was a great excuse to convince "The Boss" (read the wife) to buy a multimeter.

Both aerials Cables tested OK as did aerials.

Dropped in at a Rodio Techs in Brisbane while I was in town and the Radio was tuned 7mhz out.

All fixed for $20. On the Trip Home It was as clear as - PERFECT.

Thanks
Greg
0
FollowupID: 3831

Reply By: Member - Nigel - Sunday, Nov 03, 2002 at 01:00

Sunday, Nov 03, 2002 at 01:00
Just out of curiosity, how old was this radio?
AnswerID: 8136

Follow Up By: Member - Nigel - Sunday, Nov 03, 2002 at 01:00

Sunday, Nov 03, 2002 at 01:00
Oops, sorry - you did mention the age in the original question - Doh
0
FollowupID: 3853

Sponsored Links

Popular Products (13)