Finally got around to documenting the CB antenna installation on a buddy's FLHXS. The objectives here were:

• Look like a clean factory install
• Uncompromised CB performance

Here's the final look from back & both sides:







And here's the details:


The antenna mount is a standard 3/8 24 female stud to SO239. This mount uses a plastic isolation washer that has a shoulder on one side. The drilled hole in the H-D bracket is drilled to accept this shoulder, which insulated the coax center conductor from the threaded outer shell, which is grounded to the bike.
The M6 to 3/8 24 male to male stud was sourced from a local hardware store that "has everything" in stock. The 3/8 24 stud goes into the 3/8 24 female on the antenna mount. The H-D stubby antennas are female M6 & thread directly onto the stud adapter.


The H-D AM/FM left side mounting bracket needed a few modifications, but worked great to provide a secure bracket to use for the antenna mount.
To check for the correct antenna angle when modifying the positioning tab, I used a mechanic's parts magnet to eyeball the progress.







And here's the source for the custom coax cable used:
https://fieldcomponents.com/Coaxial-...ssemblies.html



The coax is 1/4 wavelength (108 inches) with male TNC connected directly to the CB and male UHF connector (PL259) that connects directly to the antenna mount's female UHF connector (SO239).

The VSWR on this installation was below 1.3:1 on all CB channels (with most reading 1.1:1).

 

Nice wire-up & photos, thanks.

 

 

Outstanding!!!!
I just ordered the cb antenna kit (part #76410-09) for my 2017 FLHXS, along with the bracket (part #76000183) to replace the J&M in fairing hidden antenna. The setup I currently have, sucks! Terrible range, lucky if i get 100 yards.
This is exactly what I wanted to do, but could not find any info anywhere. You have made my night! I don't think I will have to drill the bracket, since I ordered the cable kit. Do you agree?

 

The mount in the kit you ordered probably won't work; it's designed for 09-13 bikes with structure under the filler strips that looks like this mounting diagram.



Rushmore bikes (14 & later) have a different structure (reference my original post pictures).

The rest of the kit should work with the modified bracket.

I wanted to use a known high performance coax cable & knew the bracket would need to be fabricated since H-D didn't design a bracket for the CB antenna mount for Rushmore models (although they did leave the hole/grommet detail in the right filler panel). This kit uses a proprietary antenna mount/coax connector that I didn't want (braid coverage is about 70% - coax I used has braid coverage > 97%).

It also uses the oem length antenna. I knew from previous experience with optimizing the CB performance on my own bike (14 Limited) the oem CB antenna would not provide an acceptable VSWR (the oem antenna is resonant near 24.5 Mhz; CB band is 26.965-27.406 Mhz) but the H-D shorty antenna would (it's resonant in the CB band).

Those are my reasons for not ordering/using this kit. For most, the coax & antenna mount will work, but the mounting bracket will need to be fabricated. If the antenna can give you a VSWR of <1.3:1 you should get reasonable CB performance. If the antenna VSWR isn't below 3:1 you'll need to replace it (it's not a tune-able antenna).

BTW - Cost of parts (from memory so may be incorrect): CB Antenna $30, M6 stud $3, coax w/connectors $22, H-D bracket $14

 

Very nice write up and details. What type of distance are you getting now?

I installed the J&M pigtail and Y-style grounding strap. I’m SWR on the high and low channel was 1.2-1. Still barely get line of sight connectivity.

 

I have communicated bike to bike with a buddy up to roughly 1-1/2 to 1-3/4 miles. Communications of course is dependent upon many conditions, including how much band noise we are experiencing, as well as the other person's radio/antenna performance. With most bikes within our riding group, I can usually hear them farther than they can hear me, but most always 1/2 mile minimum up to maximum already stated.

Don't know what your setup is; what year & model bike and what antenna?

 

I agree with you 100%. I believe this setup will be much better than what I have. There is a local cb shop that I stumbled across today, so I will have them check the SWR reading and see if they recommend anything.
If I understand your reply correctly, it sounds like the shorty cb antenna will give me better performance than the standard size. If that is the case, I will pick up a shorty and be done with it.
I think the reason why they don't have a kit for the 2014- up models is because they are getting away from cb comms, and steering people towards the Bluetooth headsets.

 

The reason the oem length antenna doesn't work well is because it was originally used with a loading coil that was mounted inside the tour pack. Here's the picture for an antenna kit that shows the loading coil.




And the parts list from that kit doesn't even list the (omitted) loading coil.



The reason the shorty antenna works better is because it's designed to be resonant at 27 Mhz w/o using a loading coil. I worked with a fellow amateur radio operator to find improvements that provided better performance. We found, using an antenna analyzer, the oem antenna was resonant around 24.5 Mhz. Through experimentation (& destruction of 2 oem antennas in the process) we found out the oem antenna could not be trimmed in order to tune it for a low VSWR & the shorty antenna would work w/o trimming, providing an acceptable VSWR.

I spoke directly (face to face) with the H-D Electrical Engineer from the Rushmore Project in August 2014. I asked about the changes made to the CB antenna design, including components used and PTT switch design & component placement. The guy was totally clueless about everything I mentioned.

It wasn't until August 2017 that I finally got someone to listen to my suggestion about switching the PTT & Cruise Control functions side to side with a programming option in the Tech II in order to return functionality to owners. I got their attention when I told them they had pissed off their most actively loyal customers, their HOG Chapter Roads Captains that used the CBs for leading group rides. They took notes & made the changes: by October 2017 the PTT/CC swap option was finally available to owners that wanted to make the change.

My ham friend has switched from a FLHTK to a FLHXS and uses the same antenna mount (minus the M6 to 3/8 24 male stud but with a 3 foot tunable Firestik antenna. It's ugly, but provides noticeably better performance than the H-D shorty antenna (sorry, no pics of his bike).



I realize this reply is way more info than needed/requested, but I thought is was relevant to touch upon the work we did to get to where we are today with the configuration used for my buddy's bike.

 

This write up was exactly what I needed to know. Great job!!!
I am a road captain for our local HOG chapter, and that is exactly why I need a cb that works and works well.
I lead a multitude of rides, and comms are key.
Thank you so much for sharing your knowledge. It is greatly appreciated.