Article JMCB-2003 antenna set up

Joined
May 4, 2006
Messages
4
Location
beaver bank ns canada
Bike
2007 st1300
I have read on line of many people with issues with the JMCB-2003, and I believe many can be contributed to not setting up the antenna correctly. I myself have benefited from this site a lot over the years and figured I should post on my experiences and maybe it could help others.
Does your system sound like the squelch is broken all the time on WX channels, do you have trouble hearing other riders or otherwise have poor reception issues. If so it could be antenna set up. The install Manuel does not reflect or talk about the need to tune the antenna regardless if you purchased your system as kit for your model/ motorcycle.
I actual contacted J&M cooperation and found them to be very helpful. With their guidance I resolved my issues. First you will need a SWR meter. I used an Astatic PDC2 which I found on eBay for less the 20 US.


Next you will need a UHF male to male joiner I used MODE electronics UHF joiner P/N 21-266-1. Purchase locally for 3.48 Canadian. However I am sure your local electronics store should be able to hook you up.

Once you have these you will be required to hook them up in line follow the user instructions of the SWR meter you purchased all SWRs work similar, however follow the your meters instructions.

Tuning the antennae for the JMCB 2003 with an SWR Meter


Connect your SWR meter in-line as normal,,,,, and make sure that the antenna is properly grounded to the frame of the motorcycle and that there are no shorts between the center conductor of the coax and the shielded portion,,,,, ((these shorts can be caused by, among other things, the insulator pieces on the antenna mount itself being shifted to the side or installed improperly or in the wrong order)))),,,,

When you are certain that all of those things are correct, you can then proceed to SWR adjustment,
To adjust the antenna, pull the top cap off, make a very small slice in the side of the black cover material, right at the very top,,,,, then reach down in there with a needle nosed pliers and pull out about 2†of the wire at a time ,,,,
Clip it off and bend the end over the top of the antenna and replace the little cover each time you re-check the SWR readings,
The idea is to get channels one and forty to have the same SWR reading, somewhere between 1:1 and 2.5:1 ,,,,,, that way all of the other channels will have an SWR reading at or below that level ,,,,,,
If the SWR reading on channel one is lower than the reading on channel forty, you need to cut off more wire ,,,, if the SWR reading on channel 40 is lower than channel one, you have cut off too much wire ,,,, simple as that ,,,,,
When you get the SWR's where you want them, squirt a little black silicone into the top cap, before you push it back on for the final time,


I am sure if you dig into this form you will find someone that has touch or even covered this issue. However maybe this will help others with these issues. For a final note my final readings on with the unit selected on high were
ch 1= 6 watts , 1.4 SWR
ch40=2 watts , 1.6 SWR
The manufacture confirmed these values where within operation specifications.
Hope this helps good luck
 
Last edited by a moderator:
Top Bottom