Boom Box 6.5 question
Grand HDF Member
Joined: Sep 2013
Posts: 3,820
Likes: 587
From: Michigan
Last summer a friend & I set about looking into the poor CB performance on our 2014 Limited models. We used a MFJ 269C Antenna Analyzer to look at the factory antenna system. We found the stock CB antenna system was resonant around 25.5 Mhz. The CB band frequency range is 26.965 to 27.405 Mhz. We also found the antenna feed coax was
a) poor quality coax;
b) fitted with a Motorola in-line connector normally used for AM/FM (75 Ohm impedance) antenna systems;
c) that connector is NOT WEATHERPROOF but located behind the seat and has no weather protection or di-electric grease to prevent corrosion;
d) had a ground that was isolated from the main frame of the motorcycle.
Attempting to trim the stock CB antenna (done by removing the plastic tip, then trimming the mast length - shorter length equates to higher resonant frequency) was ineffective. Adding additional grounding wires from the TP mount to the rear sub-frame to the main frame did improve CB performance (per improvement mods included in J&M's CBAU-HU14 kit).
We did find we were able to get the CB antenna system below 2.9:1 by switching from the oe CB antenna to the shorter, top-loaded CB antenna. Further testing after these changes, we were able to extend bike to bike communication range to about 2-1/2 miles under good conditions.
This range improvement was acceptable for our needs, so we ended our experimentation at this point. We are both confident we could further improve the CB performance by completely replacing the poor quality coax with a good quality grade of 8X 50 Ohm impedance coax.
Last edited by Hammz; May 7, 2015 at 09:27 PM.
Tourer
Joined: Apr 2014
Posts: 257
Likes: 1
From: Kansas City, MO
SWR above 3.0 is hard on the radio finials. The higher the SWR's the harder the radio has to work to drive the signal, which will reduce your output watts. Reduces the range your signal wave will travel.
Grand HDF Member
Joined: Sep 2013
Posts: 3,820
Likes: 587
From: Michigan
Resultant observed effect is the same.
Cruiser
Joined: Nov 2007
Posts: 201
Likes: 1
From: Mahomet IL
The SWR or Standing Wave Ratio does indeed matter, as it affects both transmit & receive efficiency. Moreover, a high SWR can possibly damage the radio. Stated correctly, a unity match is not 1.0 but rather 1.0:1 because the measurement is a ratio, not a whole number.
Last summer a friend & I set about looking into the poor CB performance on our 2014 Limited models. We used a MFJ 269C Antenna Analyzer to look at the factory antenna system. We found the stock CB antenna system was resonant around 25.5 Mhz. The CB band frequency range is 26.965 to 27.405 Mhz. We also found the antenna feed coax was
a) poor quality coax;
b) fitted with a Motorola in-line connector normally used for AM/FM (75 Ohm impedance) antenna systems;
c) that connector is NOT WEATHERPROOF but located behind the seat and has no weather protection or di-electric grease to prevent corrosion;
d) had a ground that was isolated from the main frame of the motorcycle.
Attempting to trim the stock CB antenna (done by removing the plastic tip, then trimming the mast length - shorter length equates to higher resonant frequency) was ineffective. Adding additional grounding wires from the TP mount to the rear sub-frame to the main frame did improve CB performance (per improvement mods included in J&M's CBAU-HU14 kit).
We did find we were able to get the CB antenna system below 2.9:1 by switching from the oe CB antenna to the shorter, top-loaded CB antenna. Further testing after these changes, we were able to extend bike to bike communication range to about 2-1/2 miles under good conditions.
This range improvement was acceptable for our needs, so we ended our experimentation at this point. We are both confident we could further improve the CB performance by completely replacing the poor quality coax with a good quality grade of 8X 50 Ohm impedance coax.
Last summer a friend & I set about looking into the poor CB performance on our 2014 Limited models. We used a MFJ 269C Antenna Analyzer to look at the factory antenna system. We found the stock CB antenna system was resonant around 25.5 Mhz. The CB band frequency range is 26.965 to 27.405 Mhz. We also found the antenna feed coax was
a) poor quality coax;
b) fitted with a Motorola in-line connector normally used for AM/FM (75 Ohm impedance) antenna systems;
c) that connector is NOT WEATHERPROOF but located behind the seat and has no weather protection or di-electric grease to prevent corrosion;
d) had a ground that was isolated from the main frame of the motorcycle.
Attempting to trim the stock CB antenna (done by removing the plastic tip, then trimming the mast length - shorter length equates to higher resonant frequency) was ineffective. Adding additional grounding wires from the TP mount to the rear sub-frame to the main frame did improve CB performance (per improvement mods included in J&M's CBAU-HU14 kit).
We did find we were able to get the CB antenna system below 2.9:1 by switching from the oe CB antenna to the shorter, top-loaded CB antenna. Further testing after these changes, we were able to extend bike to bike communication range to about 2-1/2 miles under good conditions.
This range improvement was acceptable for our needs, so we ended our experimentation at this point. We are both confident we could further improve the CB performance by completely replacing the poor quality coax with a good quality grade of 8X 50 Ohm impedance coax.
Appreciated, if not completely understood. I would like to look into improving the usefulness of the CB on my 14 Limited.
Road Warrior
Joined: Jul 2013
Posts: 1,624
Likes: 13
From: Fort Worth
To add to this, a couple of us have also had good luck with the older metal whip antenna that used to come on the older HD with CB. I'm not sure but I don't think the antennas HD uses are the no ground plane ones so the other issue with our bikes is we have no ground plane and this adds to the very poor transmission range and higher SWR.
Last edited by FinalShot; May 8, 2015 at 10:31 AM.
I did the same thing to my 2010 FLHTCU and it was that way for a while. It didn't do any damage. Simply swapped the aerials and the radio was just fine. A lot of static and short range when they were installed incorrectly but they worked like new ones when I got them on the right posts.
Stellar HDF Member
Joined: Aug 2008
Posts: 2,060
Likes: 157
The Harley shorty antenna (http://www.harley-davidson.com/store...638609--1#tabs) is probably as good as you can get, unless like the above post stated, you want to add a better ground and coax. I get a 1.5 SWR with the shorty antenna.
I just noticed in the instructions for the antenna that the 2009 and later models use a different antenna than the 2008 and earlier bikes. My antenna only says CB at the bottom. The proper one I mentioned above says 09-CB. So it looks like I'll be stopping by my dealer to get the correct shorty CB antenna.
Now I know with this antenna (08 and earlier), the SWR is 1.5. I hope the correct 09-later shorty antenna keeps it the same or better. Guess I'll find out tomorrow.
UPDATE:
Dealer gave me the proper HD shorty cb antenna. I checked the SWR, and it's at 3.2, which is horrible. It was better with the incorrect cb antenna. I might as well use a string with a soup can on each end since Harley doesn't know how to properly tune the antenna to the cb.
I just noticed in the instructions for the antenna that the 2009 and later models use a different antenna than the 2008 and earlier bikes. My antenna only says CB at the bottom. The proper one I mentioned above says 09-CB. So it looks like I'll be stopping by my dealer to get the correct shorty CB antenna.
Now I know with this antenna (08 and earlier), the SWR is 1.5. I hope the correct 09-later shorty antenna keeps it the same or better. Guess I'll find out tomorrow.
UPDATE:
Dealer gave me the proper HD shorty cb antenna. I checked the SWR, and it's at 3.2, which is horrible. It was better with the incorrect cb antenna. I might as well use a string with a soup can on each end since Harley doesn't know how to properly tune the antenna to the cb.
Last edited by YPD485; May 9, 2015 at 05:58 PM.
Thread Starter
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6th Gear
Joined: May 2015
Posts: 11
Likes: 0
From: Alberta
Wow. I never thought I would have generated uch a long discussion on the post I wrote. I want to thank all that replied and gave some good pointers on the matter. I want to say that I also did some research on a CB radio forum. I found out that living in Southern Alberta, no one or very little people use the CB. From the foothills East to Manitoba there is very little use and also from the southern border to Edmonton. But having said that I still want it to work properly. So using your info and what I have read on the CB forum I'm gonna try and get a reading (SWR) and go from there.
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