Common UHF problems

[taslucas]

Yes it can be repaired but if it is an older system and not worth much then it is not worth doing..

There are specialist shops here that can test it but I dont know what you have down there.... mostly communication specialists.

Its a brand new 80 channel Uniden unit. I brought it over a year ago but its only been turned on for about an hour all up so i hope its not fubared. Ill ask at a communications shop, cheers

[Bloodyaussie]

They might try and up sell you so tell them you have another set up at home you will install if its beyond repair....

[taslucas]

bloody oath i hope its not beyond repair. I hope its not broken for that matter! lol, ill start with another aerial

[Clunk]

Are your mates also using 80 channel jobbies too? We were on a club trip a little while ago and we had difficulty between 40 channel and 80 channel users hearing each other on certain channels.

[taslucas]

Are your mates also using 80 channel jobbies too? We were on a club trip a little while ago and we had difficulty between 40 channel and 80 channel users hearing each other on certain channels.

hmmmmm very interesting, no i think everyone i know still has the 40 channel...

[TPC]

Hi Lucas,
If you have transmitted without an antenna you may have damaged the transmitters output amplifier, most modern radios can cope with transmitting without an antenna for short periods without damage. If you have damaged the radio you should still be able to receive ok but only be able to transmit for a short distance, if you are also having trouble receiving that sounds like a faulty antenna or cable.
The way to test it is with a SWR meter, if you were in Adelaide I could check it out for you, not sure what you could test yourself. Who installed your aerial? What sort of antenna do you have?
A "Ground Plain Independent Antenna" is the best to use as this will work more effectively in all directions and I find they work best on a gutter bracket rather than on the bulbar. I use an RFI elevated feed ground plain independent antenna and have two whips, one a 6.5 dB and the other a 1/4 wave and swap them over depending on what I am doing- 6.5 on the highway, 1/4 wave when 4wding. This link shows the difference-http://www.rfi.com.au/consumer/gain.html
Wiring to the battery is best as you have less voltage drop, positive to battery via fuse and negative to a good earth point close to the battery.

[taslucas]

Cheers TPC,
Ok so my antenna is just a real cheap cr@ppy one so the first thing ill try is a new, better quality one. I think i will try to keep it on the bullbar as theres always a lot of trees where we drive and it would probably get a caining on top of the vehicle.
So what is the 1/4 wave whip? Ive seen interchangeable whips (ie: 6.5db antenna with a 3 db interchangeable whip) but havent come across the term 1/4 whip. Does it just reduce the 6.5 to a quarter?
Thanks for the link, i have seen that diagram before and so decided that 3db is the best. It will be very rare for me to need long distance and even more rare to have a long line of sight to the next vehicle. 90% of its use is less 500 metres BUT through very densly forested and hilly terrain.
I have started looking at the GME range but theres so many varients! So far i think i need:

3db for the terrain im in (possibly with a 4.5 interchangeable whip).
Around 600-800mm tall to help help clear the roof line from the bullbar mount.
Stainless steel as opposed to fibreglass to help with tree strikes. (perhaps with one of those lock pins in the spring).
A ground plain independant.
Nice thick heavy duty/good quality coaxial cable.
And my fingers crossed that i havent wrecked my UHF unit!
Does that sound like im on the right track?

[taslucas]

Oh just another thing, what is the difference between dBi, dBd, dB, and 1/4 wave? That RFI site suggests the first three over 1/4 wave.

[threedogs]

You'll need to spend $100 on an antenna , I have a tall one mtr 6db for hwy use and a short 450mm one for hilly trips.
I ran an earth from the base to the neg on my battery. Most in my club run a very small 100mm antenna in the middle of
the roof [best spot] but not all wont a hole drilled, If antenna is on FR of 4x4 then signal is going to the RL. Not 100% sure we need 80 channels
as we have plenty ATM with 40, I for one wont be up grading even though I have an 80 channel one sitting in my cupboard.
I did have it in my camper as a home base radio,

I'll get some more info for you today

[TPC]

Oh just another thing, what is the difference between dBi, dBd, dB, and 1/4 wave? That RFI site suggests the first three over 1/4 wave.

dB is a measure of gain.
dBi is gain over a theoretical antenna that radiates out in a perfect sphere.
dBd is gain over a dipole antenna, and a dipole antenna has a gain of 2.15dBi.
dBq is gain over a 1/4 wave antenna.
A 1/4 wave antenna has a gain of .15 dBi.

When looking at gain figures look at the dBi or dBq figure.

The antenna cable used only needs to be RG58 or cellfoil if you want lower loss but get some convoluted tubing to run the cable in for protection.

Sounds like you are on the right track with the antenna style, if I get time latter on I will have a look through different antennas available for what would be good if you have not already found something.

As TD said, an antenna in the middle of the roof is best but few people want to drill a hole.
I don't like to see any wiring for the radio going direct to the negative of the battery as if you ever have an earthing issue at starter motor you can end up having the starting current go through your radio, have seen this happen at work with customers vehicles several times.