Can I shorten my UHF CB Aerial?

Submitted: Sunday, Feb 12, 2006 at 07:32
ThreadID: 30694 Views:7529 Replies:11 FollowUps:5
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Hi All,

The new 4x4 has a UHF radio and the aerial is on the fron bumper, its about 3ft long. Trouble is I have a real low, garage door and it catches everytime I go in and out.

Is it possible to just cut 3 inches off the end without having a negative impact???

Thoughts
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Reply By: Mike Harding - Sunday, Feb 12, 2006 at 07:41

Sunday, Feb 12, 2006 at 07:41
No.

Changing the length of the antenna will have a significant effect on it's performance and in the very worst case may cause damage to your radio.

Mike Harding
AnswerID: 154513

Reply By: Member - JohnR (Vic)&Moses - Sunday, Feb 12, 2006 at 07:50

Sunday, Feb 12, 2006 at 07:50
Zebu, you buy a shorter one which may be tuned with a coil in it or change the position or both. The higher the placement the better even a half wave which is also tuned length.

Can't you adjust the garage door?
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John

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AnswerID: 154515

Reply By: Member - Tony G (ACT) - Sunday, Feb 12, 2006 at 07:53

Sunday, Feb 12, 2006 at 07:53
Just but a shorter one, you can get them under 3', it will be fine for town and short trips. Then put the longer one on for outback trips
AnswerID: 154516

Follow Up By: Lone Wolf - Sunday, Feb 12, 2006 at 08:24

Sunday, Feb 12, 2006 at 08:24
I second that motion.

On both of our vehicles, we use the little 5" rubber jobs, and even then, the radio sits at work.

When we go away, we put the weapon aerial on.

Wolfie
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FollowupID: 408470

Reply By: Zebu - Sunday, Feb 12, 2006 at 08:45

Sunday, Feb 12, 2006 at 08:45
Thanks fro teh feedback - the aerail is actually only 60cm long to begin with - I need to take 15cm off. Can you get them that short?

Currently it is mounted on the top bar of the bull bar. What if I drop it down onto the base of teh bullbar. It may touch the top bar of the bull bar - will taht have a negative effect?

to be honest i never use it, and if I do its just to talk to a car in front or behind.

thoughts
AnswerID: 154518

Follow Up By: Wayne (NSW) - Sunday, Feb 12, 2006 at 08:56

Sunday, Feb 12, 2006 at 08:56
Zebu,

Putting the aerial on the bumper section of the bull bar will be OK. Cutting the length of the aerial will effect the performance of the radio.The aerial is made to a length and tuned to that length.

The aerial touching the loop of the bull bar should not effect the performance.

Wayne
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FollowupID: 408474

Follow Up By: GaryInOz (Vic) - Sunday, Feb 12, 2006 at 11:28

Sunday, Feb 12, 2006 at 11:28
"...The aerial touching the loop of the bull bar should not effect the performance...."

...until the plastic wears through on a long trip over corrugated roads, then you can kiss the output stage of the radio goodnight...

This is not a good idea.

Mount the base up high on the bullbar and use a short aerial when in convoy or thick bushes, and the longer one when out on the open road. carrying two means you have a spare (granted, not an "ideal" spare) should one break/get lost. They aren't that expensive or difficult to store...
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FollowupID: 408488

Reply By: hoyks - Sunday, Feb 12, 2006 at 10:17

Sunday, Feb 12, 2006 at 10:17
Dropping the mounting position may end up shielding the antenna with the body of the vehicle and that will affect the range of the radio.
Is it causing any damage to the door or is it just irritating? If the tip catches on the way in and out it shouldn't hurt the antenna as they are quite flexable.
AnswerID: 154531

Follow Up By: GaryInOz (Vic) - Sunday, Feb 12, 2006 at 11:29

Sunday, Feb 12, 2006 at 11:29
another trick is to tie the tip of the aerial to the roofrack with fishing line.
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FollowupID: 408489

Reply By: Michael Carey - Sunday, Feb 12, 2006 at 15:05

Sunday, Feb 12, 2006 at 15:05
Simple rule.
Put the UHF antenna up as high and in the clear as you possibly can. Anything else will be a compromise.
How much of a compromise is variable. If you want it low on the front bullbar, mounted at the bumper level... expect your VSWR to rise and performance to drop, especially to the rear of the vehicle.
I had a guy come in with a UHF and antenna he had installed. He complained that it wasn't working very well. The antenna was mounted on the tow bar tounge, the entire length was alongside metalwork. When I said it needed to be raised, the remarked that it would then hit his carport roof!
Sometimes you need to make compromises, in his case... the performace of his radio had to suffer because of the carport roof. Some people work the other way and modify the cars home to suit the additions. Or, unscrew the antenna when not in use and put up with a little inconvenience.
But NEVER, EVER cut an antenna just to make it fit !!
AnswerID: 154565

Reply By: Member - Reiner G (QLD) - Sunday, Feb 12, 2006 at 21:54

Sunday, Feb 12, 2006 at 21:54
Can't you just raise the Garage?
(sorry) I tried not to..........:-0

Reiner
AnswerID: 154628

Reply By: Truckster (Vic) - Sunday, Feb 12, 2006 at 22:20

Sunday, Feb 12, 2006 at 22:20
Why not take it off? Takes a whole 10 seconds
AnswerID: 154632

Follow Up By: V8 Troopie - Sunday, Feb 12, 2006 at 23:54

Sunday, Feb 12, 2006 at 23:54
Yes, why not. Usually the simplest solution is the best and its highly unlikely that he wants to use the UHF inside the garage.
Klaus
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FollowupID: 408625

Reply By: Patrol22 - Monday, Feb 13, 2006 at 13:01

Monday, Feb 13, 2006 at 13:01
My question is what sort of vehicle are you running and how loooooooooooooow is your garage? I've got a 3ft aerial on the top mount of the bullbar on my GU and I've gotta say I'd lose the cabin roof of the patrol before I'd have to worry about the aerial!
AnswerID: 154705

Reply By: Mike DiD - Tuesday, Feb 14, 2006 at 11:05

Tuesday, Feb 14, 2006 at 11:05
A quarter-wave whip works quite adequately -at UHF that's 15cm (6 inches).

Use that as your everyday antenna and only put on a big antenna when you need maximum range.

How easily you swap antennas depends on your current antenna. For a 1/4 wave antenna, there is no earth connection needed to the whip.

Mike
AnswerID: 154869

Reply By: geocacher (djcache) - Wednesday, Feb 15, 2006 at 01:01

Wednesday, Feb 15, 2006 at 01:01
I have an autotune on mine with a 1.5m whip on it (1.x mm stainless).

It hits my door & roof, and the doors at the ambulance station but it's not more than an annoyance.

Go the 15cm whip if it's really bothering you. (That's about a quarter wave length for 476MHz which is approximately UHF frequency - can't remember exactly but google will tell.)

Performance will be slightly affected but over convoy distances you won't notice.

Keep the other in the back for a spare.

Dave
AnswerID: 155065

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