BMW Luxury Touring Community banner

1 - 14 of 14 Posts

·
Gene
Joined
·
154 Posts
Discussion Starter #1
Just curious if anyone has shortened their radio antenna and if so was there any negative impact (i.e. reception).

Gene
 

·
Registered
Joined
·
140 Posts
I'm interested in this too, my antenna catches on the garage cross beams and I've already managed to whip the ceiling light out. :)
 

·
Registered
Joined
·
236 Posts
My lady friend caught mine in the garage door and broke off about 1.5 feet. I dont notice any difference on the FM bands but have not tried it on the AM band. I am sure that it is tuned to a specific length and is not working to its max potential in its shortened state.
 

·
Registered
Joined
·
1,435 Posts
I simply cut mine in half and put the end cap back on. The antenna length is tuned for a specific frequency, (which is a compromise since the AM and FM bands span multiple frequencies), but you can still get good results with a shorter antenna (which is therefore tuned to a higher frequency). In rural CT, my radio reception with my 1/2 length antenna is no worse then it was with the stock antenna, which means, it still sucks!

A simple FM dipole antenna for an FM transmitter (or receiver) system has it's length determined by:

The wavelength, l, of the frequency you wish to tune to (say the middle of the FM band, (108 - 87.5)/2 + 87.5 = 97.75 Mhz, by dividing the speed of light (11,784,960,000 in/sec) by the frequency (97,750,000 cycles/sec) = 120.5. Thats for a full dipole, most antennas are 1/4 dipole, or in this case about 30 in. I think the stock LT antenna is about 36 in.
 

·
Registered
Joined
·
1,492 Posts
When I remember, I tuck the end of my antenna just under the far side of the chrome luggage rack (I knew it had a use !!) before I ride into my garage and hit the 'close' button. If I forget, there are a lot of graunchy noises, but the antenna has not snapped yet.
 

·
Registered
Joined
·
205 Posts
Just call him Sir Fred!

FredR said:
My lady friend caught mine in the garage door and broke off about 1.5 feet.
What else can one say? :histerica
 

·
Registered
Joined
·
659 Posts
Go satellite radio and you can cut off however much you want....of the antenna that is!:D
 

·
Registered
Joined
·
3,208 Posts
Shortened it today

This morning I was standing next to the bike waiting for the wife to come out of the house
and getting ready to roll her (the bike) out of the garage
and have the antenna catch on the garage door like it always does.
When I thought to myself, I wonder how hard it would be to cut this thing of?
30 seconds later I was looking at 4-5 inches of antenna in my hand saying it's fiberglass,
I don't know what had me thinking it was metal?
Sprayed a little WD40 into the rubber cap and wiggled it back on,
went for a ride and didn't notice any difference,
excepting it don't piss me off catching on the overhead door no more. :)
 

·
Registered
Joined
·
300 Posts
Does it make any difference on the CB antenna....?
My CB antenna is much longer than the radio antenna.
Is anybody else having problems with the J&M CB unit?
My bike is 2006 and the CB has never transmitted correctly......?
The Dealer has worked on it three times and now I have this very tall CB antenna.
While transmitting it breaks up and nobody can understand what I said.
Someone mentioned to me this weekend there are problems with the Intercom?
My motorcycle has the BMW Comm System V.O.I.C.E. II installed by dealer
Are there problems with this intercom system that I am not aware of ?
 

·
Registered
Joined
·
1,435 Posts
All radio antennas work on the same principle, so size does matter!
 

·
Registered
Joined
·
236 Posts
zimbazi said:
Does it make any difference on the CB antenna....?
My CB antenna is much longer than the radio antenna.
Is anybody else having problems with the J&M CB unit?
My bike is 2006 and the CB has never transmitted correctly......?
?
Not sure about your intercom or your CB unit but your transmitting antenna needs to be a specific length. A standard calcuation for a full wave antenna would be 486/freq in Mhz and divide that by 4 to get to a 1/4 wave size. using 27.2Mhz as a midpoint for the cb band would result in an antenna approx 4.5 feet in length. CB antenna mfgs quite often use a coil or wind the antenna on a fibre core to keep the length down. So dont cut your CB antenna unless you have a reliable SWR meter or ant analyzer and know what your are doing or you could wipe out the final amplifier in your CB radio. Just my .02
 
1 - 14 of 14 Posts
Top