CB Antenna Question

[Bill]

For the past few years, I've been using a Firestik FG2-DD series 'No ground plane" (NGP) CB antenna on a license plate bracket mount, which I always felt delivered somewhat mediocre performance with my J&M JMCB-2003.

Recently, I added a Givi E52 with a Givi SR357 rack and it provided me with an opportunity to construct a much stronger mount and bolt it to the front section of the SR357.

Rather than simply moving the 2ft NGP antenna to the new mount, I started wondering if I would get improved performance from using a Ground Plane antenna with a 9ft Firestik FireRing coaxial cable and using a 10 gauge ground wire from the antenna mounting bar to the motorcycle frame.

Honestly, I wouldn't mind getting rid of the 17ft coaxial cable that has to be spread all over the inside of the bike.

Am I likely to improve the performance of my antenna by using a Ground Plane versus the No Ground Plane?

Since the new mounting location is to the front and right side of the E52, the antenna will be a higher than it was when mounted to the license plate bracket. Since the new mount is bolted to the SR357 and can handle more weight than the 2ft mast that I'm currently using... I'm wondering if I should just use a 3ft or 4ft mast instead? I bought a 203EZ Fold Over Adapter to accommodate covering the bike when I'm traveling and can pull into the garage without hitting the antenna on the garage door, so the longer length wouldn't be an issue.

Thanks

 

[ER RN]

Bill,

This takes me back multiple decades when I was into CBs but a ground plane antenna would give you a more uniform performance by creating its own ground plane in all directons. It is no wonder you had bad performance with a NGP antenna. Think of your bike as a rectangle and your antenna is mounted on the left rear corner that would mean that your optimum transmission and reception would be forward to the right corner based on the length of the ground plane created by the bike. I'm not sure if there is any real performance difference between the 3 or 4 footer as long as it properly tuned. You can pick up the meter you'll need to tune it at Radio Shack. Tuning requires that you shorten or lengthen the antenna whip OR the coax cable to maximize performance . Extra cable should be wound in no less than 12" loops to reduce interference wihtin the circuit. From what I saw of the adapter you mentioned I think I'd stay away from it because may affect overall performance given the pivot point...don't know for sure. Personally I'd carry a wrench to remove the antenna as needed. A couple tips: solder both of your cable connectors, use dia-electric grease on all connections and remember you can never have too many grounds.

Like I said it has been a while since I played with CBs but I used these principles with all the marine radios I've installed over the years.

Hope this helps ~Harvey

 

[Bill]

Harvey-

Thank you for your thoughts and observations. Believe it or not, I had an Amateur Radio license many years ago and your suggestions brought back a lot of what I'd forgotten about antenna theory.

I purchased the bike in 2007 with the antenna already mounted. After reading your posting, I took a very close look at how everything was installed and found these potential issues that may have interfered with the performance:

The antenna was connected to the aluminum license plate bracket mount with a Firestik K-4 Stud Mount. It uses 2 nylon shoulder washers that keep the stainless steel bolt away from the mounting bracket. I found that the hole in the mount wasn't large enough to properly seat the nylon shoulder washers and the bolt (or the antenna, for that matter) was laying against the metal of the mount. Although aluminum sucks as a grounding source, it sure would have screwed up the SWR of the antenna.

The 17ft coaxial cable that's required for a NGP antenna needs to be gathered into a large bow tie arrangement and spread out as much as possible across the available space on the bike. I found that the antenna was in a rather small bow tie arrangement and stuffed into the small area under the rear cowling by the tail light.

I rarely used the CB while riding and when I did, it was only to listen to truckers talking about where the police were spotted and which lane was blocked ahead in traffic jams. Therefore, I never thought about how things were mounted or whether it could be improved.

With the Givi E52 and the new antenna mount that I fabricated, it provides me with an opportunity to improve the performance of the CB and that's what prompted me to do the original posting.

As to the Fold Over Adapter, my 1993 Goldwing came with two of those and they never created any issues with the performance of the antennas. This is a pretty decent, and thorough article about motorcycle CB antennas: Marshalls Place and he states that the Fold Over Adapter has negligible effect upon the SWR of the antenna. I also discussed the use of these with the technical folks at Sierra Electronics and at Firestik and both agreed that there would be no issues with using one of these.

Marshall is a big advocate of using the ground plane that's actually available on a motorcycle versus relying on a No Ground Plane antenna.

Sierra Electronics and Firestik both told me that there's very little difference between a Ground Plane and a Non Ground Plane on a motorcycle. However, I'm interested in hearing from FJR1300 owners who are well-satisfied with a NGP antenna or may have even had both types on their bikes.

Thanks again

 

[TomInPA]

I'm following along. My primary bike to bike radio is a Kenwood TK3101 GMRS through an Autocom. I do ride with a group that uses CB sometimes, and for the life of me why anyone on a motorcycle would use CB escapes me. Anyway, I have an interface for the Autocom to hook into a Midland CB, and I use a 2-foot Ground-plane antenna. The problem is, the FJR is a crappy ground plane compared to a steel metric cruiser where I previously used the antenna. Truth is, I don't need that much range with the CB.

If you use the radio to ride with friends, all I can say is, leave CB behind. Once you try the FM signal with its good range and quiet, interference free transmissions, you'll never go back..except like me if you ride with a group or person that hasn't discovered modern radios.

 

[dcarver]

What you need is the MoonRaker6

And my Yeasu 401B!

..and if you really want to be an Alligator station...

:devil:

 

[Bill]

Nobody likes me well enough to let me ride with them so bike-to-bike communication is never a consideration.

I spend 99 7/8% of my time listening to XM Radio or the MP3 player built into my Garmin 2730s. The other 1/8% of the time, I want to know which lane is blocked when I'm caught in huge traffic jams and want to know which lane the truckers are attempting to move into.

I just need fairly decent reception so that I can hear what's being discussed a mile or so ahead of me.

In 4 1/2 years of ownership and around 60,000 miles, I've never transmitted on the CB.

 

[TomInPA]

I rode 7500 miles last summer with my friend Jamie across the country and back, and a good sized group of local riders here on on bike-to-bike. I really enjoy it. From Fairlaner calling out the clear gaps in traffic so we can try to keep up, to Madmike exclaiming "weeeee" over the rollers, it is a gas. More recently, I was aware of Puppychow having a flat tire, and rather than being five miles up the road by the time I knew, I was able to just find a safe place to stop. The transcontinental trip was great. Rather than miles of isolation, each of us could make diversions and plans and stay in touch in spite of being separated by several miles at times. Mostly the radio is not intrusive, but when you want it, there is no substitute.

I would think that for CB reception only, there must be a simple solution, and I don't think ground plane even comes into the reception equation; however I'm prepared to be heckled for being wrong.

 

[ER RN]

Harvey-

Thank you for your thoughts and observations. Believe it or not, I had an Amateur Radio license many years ago and your suggestions brought back a lot of what I'd forgotten about antenna theory.

I purchased the bike in 2007 with the antenna already mounted. After reading your posting, I took a very close look at how everything was installed and found these potential issues that may have interfered with the performance:

The antenna was connected to the aluminum license plate bracket mount with a Firestik K-4 Stud Mount. It uses 2 nylon shoulder washers that keep the stainless steel bolt away from the mounting bracket. I found that the hole in the mount wasn't large enough to properly seat the nylon shoulder washers and the bolt (or the antenna, for that matter) was laying against the metal of the mount. Although aluminum sucks as a grounding source, it sure would have screwed up the SWR of the antenna.

The 17ft coaxial cable that's required for a NGP antenna needs to be gathered into a large bow tie arrangement and spread out as much as possible across the available space on the bike. I found that the antenna was in a rather small bow tie arrangement and stuffed into the small area under the rear cowling by the tail light.

I rarely used the CB while riding and when I did, it was only to listen to truckers talking about where the police were spotted and which lane was blocked ahead in traffic jams. Therefore, I never thought about how things were mounted or whether it could be improved.

With the Givi E52 and the new antenna mount that I fabricated, it provides me with an opportunity to improve the performance of the CB and that's what prompted me to do the original posting.

As to the Fold Over Adapter, my 1993 Goldwing came with two of those and they never created any issues with the performance of the antennas. This is a pretty decent, and thorough article about motorcycle CB antennas: Marshalls Place and he states that the Fold Over Adapter has negligible effect upon the SWR of the antenna. I also discussed the use of these with the technical folks at Sierra Electronics and at Firestik and both agreed that there would be no issues with using one of these.

Marshall is a big advocate of using the ground plane that's actually available on a motorcycle versus relying on a No Ground Plane antenna.

Sierra Electronics and Firestik both told me that there's very little difference between a Ground Plane and a Non Ground Plane on a motorcycle. However, I'm interested in hearing from FJR1300 owners who are well-satisfied with a NGP antenna or may have even had both types on their bikes.

Thanks again

No problem. It's obvious that CB radios have moved on without me I'll retract my statement about the adapter because your posting reminded me of a similar product we used on boats that were too tall to get under some bridges with the antenna extended. Their VHFs worked just fine. Good luck with your install.

~Harvey

 

[timk]

i recently installed a J&M unit without the fold over thing. It's got a 1.2/1 SW<R in the mid channels.I'm going to put a fold over on it. When I do, I will be effectively making the antenna longer,so a SWR antenna adjust is in order???????????

 

[Colin24]

I dont know about ground plane versus non-ground plane. But the single best thing I ever did was get an antenna with a tunable tip (little thumbscrew in the end) and a SWR meter and make sure it was tuned properly for the installation.

FWIW: I am running a 3 ft firefly (I think thats the name). Its a little lighter weight and whippier than their heavier firestick. I bought a 4ft firestick once but never installed it because the thing was way too heavy for anywhere I was going to mount it. I've found the 3ft is a reasonable size: big enough for good reception and short enough to fit in the garage without wacking the top. Something the J&M 4ft antenna was always doing.

 

[ionbeam]

i recently installed a J&M unit without the fold over thing. It's got a 1.2/1 SW<R in the mid channels.I'm going to put a fold over on it. When I do, I will be effectively making the antenna longer,so a SWR antenna adjust is in order???????????

The extra length of the fold-over is below the feed point of the antenna so it shouldn't affect the SWR, but if you can easily check it you probably should. If your SWR reading is while mounted on your bike that is awesome. Usually a SWR reading that dips out at 2.1 is a strong indication of a ground plane issue and in some limited cases a problem with the RG cable.

 

[Bill]

i recently installed a J&M unit without the fold over thing. It's got a 1.2/1 SW<R in the mid channels.I'm going to put a fold over on it. When I do, I will be effectively making the antenna longer,so a SWR antenna adjust is in order???????????

The extra length of the fold-over is below the feed point of the antenna so it shouldn't affect the SWR, but if you can easily check it you probably should. If your SWR reading is while mounted on your bike that is awesome. Usually a SWR reading that dips out at 2.1 is a strong indication of a ground plane issue and in some limited cases a problem with the RG cable.

That's interesting and I wouldn't have thought of where the feed point of the antenna was.

My thought was that the coaxial cable was attached to the bottom of a stud mount and that the mount was electrically part of the antenna but after reading your posting, I realized that everything below the base of the actual antenna is really nothing but an extension of the center of the coaxial cable and not part of the antenna.

Thanks for pointing that out.