CB Radio antenna mounting

I went to a local shop that install CB on motorhome. They say the no ground antenna will work well to communicate between motorhome and this is what they install now. The antenna have to be mounted with a lenght over the top of the MH. They will test it and find the proper spot to be mounted.

They did install grounded antenna before but he said it was a hit and miss to find a good ground. Since the antenna have to be mounted above the MH, ground is hard to find and not sure if it connects properly with the rest of the MH He also said sometimes they had trouble with ground noise or spoty reception with a grounded antena on a fiberglass MH, hence, they do not install grounded antenna anymore on MH.

Back in the days when motorhomes had 'west coast' trucker style mirrors, mounted with stainless or chrome steel tube, the CB antenna(s) mounted to the mirror brackets. Sadly, with the advent of fancy all plastic 'aero' mirrors, that is no longer possible...

If your motorhome has a roof rack or a ladder, you can use a mirror style mount bolted to the rack or ladder. It will make for a very long coax cable, but so be it. Should work about as well as an old style mirror mounted antenna, as far as ground plane is concerned.

If you're not towing anything, or have an extra receiver box hitch available on the bumper, you could make an L-shaped pole that slides into the receiver hitch tube and extends up to roof level. Either a 4 sq ft piece of thick sheet metal, or 3 or 4 horizontal radials about 2 ft long each will act as a ground plane on top of the pole, with the antenna mounted above. An interesting but effective home made antenna that will do the trick for short ranges.

Kidoo wrote:
The Glass mount antenna looks like a good looking set up, but will it perform? It has no ground and energy workd through the window? I have doubt on that system.

yes, I have them in all of my vehicles now and they work just fine. I have that Midland one linked to. not as good as the "best" but you are not talking about extremely long ranges here. one thing i discovered on my Bounder. they do NOT work on dual pain windows. :)
bumpy

Kidoo wrote:
Hi, I am looking for information about mounting a CB antenna on a class A. I do not plan to use this set up for very long, just for a trip with a bunch of others with CBs.

I read it needs a good ground to perform well. The problem is to ground the antenna on the fiberglass frame. I have an aluminum roof so a magnet is out of the question.

I saw a Firefly fiberglass antenna but it also need a ground.

Can I run a wire grounded to the frame from below the RV instead of screwing in the fiber? Really do not want holes in the fiber.

I also read it needs to stick out on top of the MH by half it's lenght otherwise it will not perform well, an that a 4 feet antenna is the minimum lenght.

I do have an old two part antenna with a magnet but I don't think I can fit it without the magnet.

Thanks, please share your experince.

Well, you could write a book on the topic of antennas (actually, there are books written on antennas), but in short it's going to be hard to do what you want. An antenna needs a good radio frequency (RF) ground to work well and the RF ground is essentially the other half of the antenna. An aluminum roof would make a great RF ground, but you'd need to bond the antenna to the roof, which is sounds like you're not willing to do. The metal chassis of the motor home is too far away from the antenna to work well. A no-ground-plane antenna such as the Firestik brand mentioned above) is OK, but NGP antennas operate at only a fraction of the efficiency of grounded antennas. Add to this that short antennas don't work as well as longer ones, base-loaded isn't as good as center-loaded, CB radios are limited to 4 watts (unless everyone in the group goes to SSB), etc. etc. etc., and getting a consistent range of a couple miles is a challenge.

I only use the CB radio for keeping in touch with truckers (such as in a traffic tie-up) so range has never been much of an issue for me. I use a 3' Firestik NGP antenna, with their 3-way mount and a spring-loaded base, as high up on the side of the roof pillar as I thought I could get without the antenna turning into a tree trimmer. As posted above, that's probably your best option given the realities of radio communications. I've never tested the range but I'd guess it's only about a mile consistently, depending on terrain. Over flat terrain, line-of-sight it might get to your 2-mile objective, but my guess is that's about as much as I'd hope for. I know that manufacturers claim that a 3' NGP antenna will have a range of "up to" 5 miles over flat terrain, but that seems too cheery to me. (By contrast, my ham radio 2-meter transceiver in the motor home, with an output of 50 watts run into a 1/2-wave antenna (which doesn't require a ground plane) mounted on the other roof pillar has a consistent range of 10-20 miles. Which is why I'd be surprised if a CB with a NGP antenna can get "up to" 5 miles consistently, i.e. 25-50% of the 2-meter range.)

Sorry this isn't better news, but I've been doing radio stuff for decades and reality has started to sink in. :)

Skip

If you really have an aluminum roof, get an sheet of galvanized steel. It should be thin enough so you can form it to the roof, but not too thin as it will need to hold the antenna wind load. Tape the steel to the roof and it will form a capacitive coupling to the aluminum to be the ground plane.

If you have an EDPM roof, you are done.

Matt

The Glass mount antenna looks like a good looking set up, but will it perform? It has no ground and energy workd through the window? I have doubt on that system.

RoyB, If I mount it on the mirror, it will not pass the top of the MH. I wonder how much distance I would loose.

One thing is that I could probably ground it through the miror mounting bolt, which should be screwed on metal.

Through the door opening would be a good place to run the wire then I would not have to drill any hole.

Kidoo wrote:
Hi, I am looking for information about mounting a CB antenna on a class A. I do not plan to use this set up for very long, just for a trip with a bunch of others with CBs.

For a temporary and simple setup, have you considered a glass-mount antenna like the Midland 18-258 40-Channel CB glass-mount antenna.

If it was me I would pickup a REAR MIRROR Antenna mount that looks something like this... Used to find them at Radio Shacks but now you can't find Radio Shacks any more. AMAZON will carry them if you can find a part number...



Mount it on passenger side where the door is so you can run the coax through the weather strip on the door.

If you mount it up high on top of the RV you are only going to knock it off going under something. No fun in that just to gain a few more hunder feet of range.

CB RADIO is more or less line of sight using the 27MHZ frequncies and the radiated power is very low wattage... Have no idea what bands CB'er use in Canada - Probably same as US being 27mhz...

Running with a group alot of folks would do just as well using one of the portable CB units with walkie talkie type antenna...

I wouldn't spend alot of monies on your antenna setup. Make it as simple as you can. You can mount on top of the MH and do all those things everyone says to do and all you will possible gain is maybe a few hundred feet more - 1/2 mile at the most... haha...

Having said all of this by nature of the 27MHZ you can work half way around the world when the bands are open. CB frequencies bounce of the atmosphere by multiples of 1500miles as I recall... Locally you would be hard to talk to anyone mobile to mobile as far as a mile away from you. That would be stretching things...

Roy Ken

It need to work for at least a couple miles.