UHF Aerials

Submitted: Wednesday, May 05, 2004 at 13:16
ThreadID: 12626 Views:3117 Replies:6 FollowUps:12
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I did not buy an aerial yesterday when I ordered the TX3200 as I did not have time to see what type of mounting I needed.
On doing a little bit more research with my limited knowledge would it be correct in saying a 4.5dB ground independent antenna would be the most suitable?
Many thanks again for further assistance.
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Reply By: Rosco - Bris. - Wednesday, May 05, 2004 at 13:49

Wednesday, May 05, 2004 at 13:49
I would suggest a unity gain stubby job and a 6/9dB.

The stubbies are cheap as chips and good for mountainous terrain.
AnswerID: 57306

Reply By: The Banjo - Wednesday, May 05, 2004 at 13:53

Wednesday, May 05, 2004 at 13:53
Have a look at GME's website - they explain that UHF antenna styles are made to suit certain situations (terrain mostly)..... can't have one model to do all......as mentioned above, the modular 6/9 db job is a good start - alters to suit certain circumstances.
AnswerID: 57308

Reply By: Member - Roachie (SA) - Wednesday, May 05, 2004 at 14:18

Wednesday, May 05, 2004 at 14:18
Walter,
I've used everything from "broomstick" type to a little 6" floppy job.
I was led to believe there is substantial differences and if you were to measure it with some sophisticated equipment, maybe there is.
However, from what I have seen, it makes stuff-all difference which type of antenna you use.
The only thing I would say is that it is preferrable to use a ground-plane independant base if mounting on a bullbar etc.
If you are able to (or silly enough LOL) to mount it in the middle of your roof (cutting a decent size hole for cable to go through), you would need that feature.
I just use a 6db independant ground plane on a sprung base on my bullbar and it works well (although I admit I cannot hear quite as far distances as some others in our club who have different types).
AnswerID: 57314

Follow Up By: Member - Jeff M (WA) - Wednesday, May 05, 2004 at 14:37

Wednesday, May 05, 2004 at 14:37
I agree with you Roachie, It's got a lot more to do with mounting position, cable length/quality than it does the type of arial. I've had 9, 6, 4.5 and am now using a 2.5db Dipole that cost $27 at it is performing better than all the above because I have it higher and have a the proper length of good cable hooked up.
I've seen people with $160+ arials, mounted to the bottom of their bullbars with 5m of cable curled up under the dash wondering why it doesn't work so good. A little change can make a big difference with UHF.
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Follow Up By: Walter Here - Wednesday, May 05, 2004 at 19:02

Wednesday, May 05, 2004 at 19:02
I will have to mount the antenna on the bull bar on the right hand side.
I have the radio aerial mounted on the left hand side of the bull bar due to the roof rack making the standard aerial useless.
I have an aluminium roof rack that is fully sheeted and will block the aerial to the rear. I did look at the GME website and unfortunately it does not show you the affects of say mounting the antenna in different positions.
I will go for an independent ground plane and mount it on the top rail of the bull bar to try to achieve better height. It did surprise me the price of antennas for a bit of twisted and bent wire.
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Reply By: Member - Jeff M (WA) - Wednesday, May 05, 2004 at 19:07

Wednesday, May 05, 2004 at 19:07
Walter, why not mount the aerial to the roof rack? Sure it does not look as good as on the bullbar, but the performance difference would be huge, getting above all the metal of the car and the roof rack for clear line of sight. Also less cable would be required = less signal loss. If you worried about height, just got a small little aerial, mine is only about 25cm high and works a treat. Bigger does not mean better with UHF. You are transmitting mainly from the base of your aerial so it doesn't mattery how tall it is above the car, just as long as the base is above the car. But you are correct, go the ground independant in whichever one you decide.
AnswerID: 57347

Follow Up By: Walter Here - Wednesday, May 05, 2004 at 19:42

Wednesday, May 05, 2004 at 19:42
Jeff when I have the roof rack folded open for the differential GPS and satellite equipment to operate the vehicle is 2.7 metres high. I did think of mounting the aerial up there. Getting the cable up there neatly would not be easy. I really did not want to increase the overall height.
The major problem I have found is finding proper advice. Some tell me to get a 9dB antenna, others tell me 3dB and a shortie. I am a mug when it comes to this UHF. I had no idea that the transmitting power comes form the base. Dick Smith has a ground independent aerial that is not to long and clumsy. I think it was 3dB. The GME AE4012/7K2 is 4.5db and another aerial I fancy. What do you think
http://www.gme.net.au/land/ants_uhf.html
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Follow Up By: Member - Jeff M (WA) - Thursday, May 06, 2004 at 10:59

Thursday, May 06, 2004 at 10:59
Have a look at this website:
GME Antennas
I use the following atenna listed on that website as number 3: AE4005 3dB 370mm .

Works a treat, cheap as chips, better than my big aliminium dipoles, 6db whips etc.

Just get it as high as you can, make sure your lead does not have heaps of extra cable, make it nice and lean and it'll work magic. These atennas are tuned for SWR in the factory but I reckon they tune them to run with a little less cable as they don't expect you to use it all very oftern. But less cable will give you greater reception and more power when you transmit as long as it doesn't throw the SWR out too much. I cut about 1.5m of mine and it's amazing the difference it makes in both RX and TX.
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Follow Up By: DiesAl - Thursday, May 06, 2004 at 13:14

Thursday, May 06, 2004 at 13:14
Gday Jeff, I just purchased my UHF and was advised by the dealer not to cut the length of the cable supplied but being a novice myself I'd probably believe anything they told me. Maybe I should get hold of a SWR meter and experiment with cable length. Do you know if the SWR meters that were used in setting up old AM cb's also work on UHF or doesn't it matter ?
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Follow Up By: Walter Here - Thursday, May 06, 2004 at 15:35

Thursday, May 06, 2004 at 15:35
Jeff I ended up buying that AE4005 antenna. Was $30 and ground plane independent when everything else was a $100. I did cut the cable and see DiesAl post below. What is correct? I must have cut off at least 2 metres of cable. There are no instructions with the antenna telling you not to cut the cable. If they did not want you to cut the cable I would have thought they would tell you that and fitted the plug on the end.
Thanks for the info, range is all I want after making some test calls and finding out where the people were calling from.
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Follow Up By: Member - Jeff M (WA) - Thursday, May 06, 2004 at 16:40

Thursday, May 06, 2004 at 16:40
Good on ya cobber, nah you'll be right with 2m off. The only time it would really be an issue was if it thew your SWR out a fair bit and you were talking for ages and ages it might get a little hot, but I wouldn'nt worry about it, the GME's come a little under spec'd out the factory and a lot of people tweak them up a little without any dramas, so you'll be fine!
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Follow Up By: Walter Here - Thursday, May 06, 2004 at 17:26

Thursday, May 06, 2004 at 17:26
Jeff I measured the cable I cut off and it was just over 3 metres.
The set appears to work ok. I went out this afternoon and called a few guys up and had about 10 k range as the crow flies and crystal clear. Pretty crook GME do not give you any instructions in the antenna packet about cutting the cable. I may give them a call tomorrow to find out what the go is.
The question is to cut or not to cut.
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Follow Up By: Member - Jeff M (WA) - Thursday, May 06, 2004 at 17:53

Thursday, May 06, 2004 at 17:53
How long was the cable to start with??
If you're getting 10k's crystal clear there can't be too much wrong.
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Follow Up By: Walter Here - Thursday, May 06, 2004 at 18:51

Thursday, May 06, 2004 at 18:51
Jeff the cable was originally 5.5 metres it is now 2.3 metres. Well that is what I thought 10k was good. I started looking at the truckies and what they have in the way of aerials. The truckies only have fairly short aerials and sure some were the AE4005. I do not mind spending dollars but I think you are right about the AE4005 as a bargain functional antenna. I had no idea what to buy and decided to try your recommendation. Nothing like experience from a user, and could not really justify a $100 or a large big fat tall antenna. I could call up the repeater station 9 km away without any problems and got calls back.
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Follow Up By: Member - Jeff M (WA) - Thursday, May 06, 2004 at 18:58

Thursday, May 06, 2004 at 18:58
Yeah you're spot on, the reason truckies get out so well is because they are so high, above all the other crap. I've been having a quite pleasant conversation on the ol' UHF at the lights and had a truck pull up next to me and it's gone, I get nothing because they have blocked my signal with their great huge bloody sea containers and crap. But it's the same if you have you're antenna below the bonnet line on you're bull bar, you're whole car is blocking it from behind.
9km's in a repeater should be easy peasy with your're setup. If you can do 9km "simplex" talking to somone else without the repeater then you'll know you're on the right track. However conditions will vary how well this will work. If you are both on hills, should still be easy, however the slightest bit of crap between you, tree, houses, hills, whatever and it may make it not so good very quickly.
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Reply By: Phil G - Wednesday, May 05, 2004 at 19:52

Wednesday, May 05, 2004 at 19:52
Ground independant swing-down base, with a stubbie aerial, mounted on the roof or roofrack is what I use 99% of the time now. Works as good or better than any bullbar mounted aerial, and will not break. I carry a 4.5 Db as well, but rarely use it now.
AnswerID: 57350

Reply By: Member - Bernie. (Vic) - Wednesday, May 05, 2004 at 19:53

Wednesday, May 05, 2004 at 19:53
Hi Walter
Be wary of the wire type aerial as they break at the base if subjected to corrigated or rough roads, I now always carry a stubby aerial in the glove box as a spare as a dead aerial means no radio.

Cheers
AnswerID: 57351

Follow Up By: Member - Nigel (QLD) - Thursday, May 06, 2004 at 08:41

Thursday, May 06, 2004 at 08:41
My GME wire antenna hasn't broken after 4 years, and even the bitumen roads are corrugated up here :)
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