CB Module in 2017/2018 Ultra Limited
Intermediate
Joined: Dec 2017
Posts: 34
Likes: 14
From: TN
I'd have to agree. If you are having those difficulties, something is wrong. Transmit and receive of 1 to 2 miles is about right. You can't expect much more out of 2 to 3 watts into the OEM compromise antenna.... The shorty antenna is even more of a compromise. Hidden antennas even more so. ( I've run simulations on them.... I'm an engineer... I can't help it)
I installed mine on a 2017 ultra classic. I used the JM Audio kit to replace the coax and bond the travel trunk ground plate to the frame. When I checked the SWR on the antenna, I found it to be tuned low in frequency. After trimming it a bit, I was able to get the SWR down to an acceptable level.
The JM audio kit bonding straps are simply 1/4" copper braid covered in shrink tubing with crimped lugs. Adding that bonding creates a better RF ground than the travel trunk plate alone.
A good RF ground is key to preventing feedback and garble in the transmit. Without a good RF ground, the coax shield and the case of the radio becomes the RF ground (the reason for the garble). This is called common mode current. In extreme cases, ferrite beads can be added to the coax at the base of the antenna to reduce the common mode current.
The OEM 36" antenna is a base loaded 1/4 wave antenna. It can easily be tuned by removing the plastic tip and carefully cutting the fiberglass and internal conductor. When tuned the tip can be replaced by sanding the cut end into a slight taper and re-inserting it into the plastic tip. Antenna efficiency is loosely proportional to the SWR. Therefore range is loosely proportional to SWR. Usually an SWR better than 2:1 is sufficient. My SWR on channel 19 is 1.5:1 trailing off to 1.8:1 on channels 1 and 40.
So the moral of the story if you want to improve the range and performance of the CB is to check and improve the RF ground, use the least compromise antenna and then carefully tune the antenna.
I installed mine on a 2017 ultra classic. I used the JM Audio kit to replace the coax and bond the travel trunk ground plate to the frame. When I checked the SWR on the antenna, I found it to be tuned low in frequency. After trimming it a bit, I was able to get the SWR down to an acceptable level.
The JM audio kit bonding straps are simply 1/4" copper braid covered in shrink tubing with crimped lugs. Adding that bonding creates a better RF ground than the travel trunk plate alone.
A good RF ground is key to preventing feedback and garble in the transmit. Without a good RF ground, the coax shield and the case of the radio becomes the RF ground (the reason for the garble). This is called common mode current. In extreme cases, ferrite beads can be added to the coax at the base of the antenna to reduce the common mode current.
The OEM 36" antenna is a base loaded 1/4 wave antenna. It can easily be tuned by removing the plastic tip and carefully cutting the fiberglass and internal conductor. When tuned the tip can be replaced by sanding the cut end into a slight taper and re-inserting it into the plastic tip. Antenna efficiency is loosely proportional to the SWR. Therefore range is loosely proportional to SWR. Usually an SWR better than 2:1 is sufficient. My SWR on channel 19 is 1.5:1 trailing off to 1.8:1 on channels 1 and 40.
So the moral of the story if you want to improve the range and performance of the CB is to check and improve the RF ground, use the least compromise antenna and then carefully tune the antenna.
This.....Great advice. The OEM antenna is able to be adjust to get the SWR into check. I know some state it isn't but that's not the case. I was able to get my SWR down from over 2 to under 1.6 depending on channel swing.
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flattracker60
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Jul 27, 2010 11:23 AM
