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Cutting down a UHF Aerials
Posted: Mon Jan 26, 2009 9:13 pm
by Green_Troll
Is it possible to successfully cut down a UHF Aerial. I need to cut about 200mm of a midrange 4x4 UHF Aerial. Does it work? Need to do this, because it doesn't fit in the garage anymore, and I don't feel like buying a new one.
Posted: Mon Jan 26, 2009 9:17 pm
by Micky-Lux
Generally not.
The aerial is a tuned length - that is the length of it is a set fraction of a wavelength, which gives it its resonant frequency. Chopping length off the top will change this, and if you have access to a forward/reverse power meter, you will be able to calculate that its VSWR (voltage standing wave ratio) is less than ideal. Ideal is a VSWR of 1, but generally 1.5 or so is acceptable.
You can't get a shorter whip?
Posted: Tue Jan 27, 2009 12:44 am
by DamTriton
You can get 6" helical wound "stubbies" for less than $20..............
Or you can blow the output stages of your radio for free (cost ~$100-200 to fix)......
Simple maths, really.
Posted: Tue Jan 27, 2009 7:35 pm
by Green_Troll
true, true, I'll just have to stop being tight arse thanks anyways
Posted: Tue Jan 27, 2009 8:58 pm
by jet-6
Most good communication specialists/workshops can custom tune your antenna, but your better off just asking them for the best item to suit you, pick a size and they will be able to make something to match up
But dont just chop it, as said above you will burn out your "output" if you end up with to much "feedback" in simple terms
Posted: Tue Jan 27, 2009 9:05 pm
by Canyonero 4x4
Can you just move it?
Posted: Wed Jan 28, 2009 8:41 pm
by DamTriton
Simple answer and most effective is to buy two aerials, one 6 to 9 dB and one 3 dB. Reason being the 6+ dB will be good for the trip out to wherever (on the flat in convoy) and the 3 dB is far better in hilly country. Best bit is you have a "spare" if one breaks (even if it is not the best one for the job).
Posted: Sat Jan 31, 2009 10:51 pm
by lokka
DAMKIA wrote:Simple answer and most effective is to buy two aerials, one 6 to 9 dB and one 3 dB. Reason being the 6+ dB will be good for the trip out to wherever (on the flat in convoy) and the 3 dB is far better in hilly country. Best bit is you have a "spare" if one breaks (even if it is not the best one for the job).
This is the best way to go i use a 7.5db laser for road trips and a 3db RF! mopole for general use the mopole is of a wire eliment and only stands 250MM high and works great with 30watts
