kdoddrell Posted September 7, 2009 Share Posted September 7, 2009 I had my dealer install the BMW branded J&M CB radio. This is well after my own attempt at getting a Midland to work and then gave up in frustration. So the dealer installed it and also installed the BMW antenna on the front of the bike. This is the stock radio aerial which is modified by BMW to work as a CB antenna. So should be neat and tidy, really. Recieving on the CB system is absolutely fine, but when I transmit it is OK if the bikes are a few feet from each other, but as soon as we are 50 feet apart, then the static for my riding partner overshadows the voice. I still have in the bike an obsolete 12 foor antenna cable running under the tank and seat which was used for the original antenna on the back of the bike. Would this affect the ability to transmit? If anyone has any ideas, I would be very grateful to hear!!! Thanks Kevin Link to comment
OoPEZoO Posted September 7, 2009 Share Posted September 7, 2009 My number one suspect there would be that the antenna is poorly tuned/matched to the CB radio. I don't know what BMW does to make the radio antenna work double duty, but from my CB experience.......I wouldn't trust it. I would buy and install a tunable Firestick, and then properly tune it using a SWR meter. CB's are VERY sensitive to antenna tuning, especially for transmitting. Link to comment
vizhip Posted September 8, 2009 Share Posted September 8, 2009 So the dealer installed it and also installed the BMW antenna on the front of the bike. This is the stock radio aerial which is modified by BMW to work as a CB antenna. Kevin - I am betting your antenna is your problem... As Keith said... CB's are really picky with antenna set-ups... I am trying to remember, but I seem to recall that you want the antenna length and cable length combined to be divisible by 7... but... regardless... a SWR meter will definitely help you tune the antenna to the proper adjustment... You might be better off purchasing a CB Firestick antenna with a top load or bottom load - one that does not require a ground-plane, the adjustable antenna's keep you from having to cut and redo the cable connections... but... if you purchase a proper antenna and place it on the back of the bike and use the old cable, I think you will find it will work better for you... simply because it is the proper antenna... Regards - -Bob Link to comment
kdoddrell Posted September 8, 2009 Author Share Posted September 8, 2009 Thanks Guys, I was sort of afraid someone would say go back to the firestick. That was what I had on the back of the bike and suspect that it wasn't just tuned properly. I should have researched it better before getting them to put the BMW antenna in. When using an SWR meter, do you hook it up between the antenna and the unit where they plug together? Sorry about the nerdy question. I ask because the dealer has the plug under the tank! The drama continues..... Link to comment
OoPEZoO Posted September 8, 2009 Share Posted September 8, 2009 Yes.....the SWR meter goes between the unit and the antenna (where ever that connection might be made). Idealy, you want the meter as close to the CB unit as possible. When using one with a standard CB, they usually connect right to the antenna jack on the back of the radio. You then key the mike and tune the antenna for the lowest SWR reading that you can get. I realize that is not the ideal situation if your antenna connection is buried somewhere on the bike, but it will give you the best results. Link to comment
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