CB antena

[John8545]

Missing my CB on road, planning to install my own, but I'm interested in type and location to best place, use, antenna. Also, what brand are you using? Thanks for help, and happy travels.

[Lloyd]

Antenna Specialist. Get the one with the base loaded coil.
When you mount it make sure you get the mounting screws into some metal. Preferably if you have aluminum studs in your rig, mount it on one of those. Otherwise you won't have ground and the radio won't work and probably do damage.
Also, mount it up high so it clears the rig. If you mount it down on the side you will never get the standing wave in line. Again, it won't function properly.

[John8545]

Thank you for help, I just have to get off my butt to do it. Have a good day!

[FW28z]

As a general principle, the higher you mount the antenna, the longer range you will have, and the closer the antenna length is to a multiple of the wavelength, the more efficient the antenna.

At at the 27Mhz frequency range of the CB band, the wavelength is 36ft. This is obviously too long to be practical for a mobile antenna, so typically antennas use a fraction, such as a 1/4 wave. This is not quite as efficient as a full-wavelength antenna, but a 1/4 wave antenna at 27Mhz will still be 9ft. (102") in length.

This is still too long for most vehicle or mobile applications, so to reduce the antenna length further, portable antennas typically use a loading coil (sometimes called a loaded antenna).

But a loading coil antenna is not preferable, as it cannot "capture" the signal as efficiently as a longer (non-loading coil) antenna. In reality, all the loading coil does is make the antenna appear to be a 9ft antenna to the transmitter to provide the proper load (hence the name loading coil), yet allows the physical length of the antenna to be shorter for mobile use.

Since a 9ft antenna is not practical for most vehicle applications, most people use a loading coil approach even though it is not as efficient.

If you have ever seen a bumper mount 9ft antenna on a vehicle, that is what is going on. So, for maximum performance, find a 9ft whip antenna and hopefully try and find a good mounting location for it - or just accept the additional signal loss and use a shorter loaded coil antenna for convenience.

Again, the higher and longer the antenna (minding the wavelength 1/multiple caveat), the better.

[John8545]

Thank you for great info, now, on class A MH, where and kind of antenna would you suggest? Thank you for help.

[FW28z]

I suppose it depends on how heavy duty of a CBer you are and if you are going to travel all the time or park for awhile.

If you want the best performance and are going to be in one locale for a long period of time, I would consider a 102"/9ft whip. If you mount it to the roof of your moho it would work well. However, this means you would have to take the antenna down each time you move, so it would not be practical if you were on the go frequently.

Obviously you would need some kind of lay-down mount for the 9ft antenna.

You could also mount a small loaded coil antenna on the roof without much issue.

Which antenna that is best for you depends on whether you are a "mover" rather than a "parker". If you are a mover, you will want a loaded coil antenna and accept the losses. If you are a parker, then you will probably want a 9ft'er for times you will be there awhile (that you take down before moving), as well as a shorter loaded coil antenna for times you are on the go (that you don't have to take down).

One other issue I see is some RV parks might not allow you to use such an antenna. I know of a ham radio owner that moved to a trailer park in Florida that did not allow such antennas. So he disguised the antenna inside of a fiberglass flag pole. So perhaps you could get one of those Flag Buddy things and do something similar. You might need to get creative (fiberglass is transparent to RF radiation). That way though, you could raise the antenna without getting on the roof of the coach or permanently mounting anything.

Again, it depends on how much you are into it. Obviously, the longer antenna will perform better, but it will be more of a hassle to fiddle with.

Either way, one thing Thor does with their motorhomes is they build in a steel plate in the roof for mounting a satellite dish. On my rig for instance, there is a 36"x36" steel plate embedded in the roof for the dish.

This would be a good location to mount an antenna unless you have or are going to install a satellite dish.

If so, there may be other locations as well, such as where the ladder attaches to the top. On my rig, there is a 26"x30" mounting pad on the roof for attachment of the ladder, which might provide enough space for mounting an antenna adjacent to the ladder.

What I did is I contacted Thor and asked about mounting locations on the roof and asked for a drawing. They sent me one almost immediately, which provides all of the dimensions of the various mounting steel plates in the roof, as well as where the aluminum support beams are.

One caveat though, the way RV manufacturing seems to be, I'd confirm the locations with a wall nail finder magnet thingie to make sure the drawings are truly as-builts for your rig.

Otherwise the next best location - at least for a short antenna (it may not work well for a 9ft antenna), is at the top of the ladder itself. You should be able to put a mirror mount type of antenna mount there and fasten a short antenna to it.

The only issue I see with this mounting location is the possible interference with your backup camera when you transmit. I rather doubt the camera cabling is shielded very well, and transmitting near the camera cable could induce some noise or interference.

So, I'd fully test everything out prior to drilling a hole in anything.

One thing though with Class A rigs - they are sometimes taller than Class C, so you may want to concentrate putting the antenna on the left side as that may give you maximum clearance for bridges, etc.

[Lloyd]

I agree with most of what FW28z has stated. The problem with 102 in. whip is it's just to long and would be totally impractical for a MH install.
As far as the base loaded coils, my experience with the antenna specialist brand (M125) has proven them to be very good.
Lets face it, there is only 5 watts on a CB radio, any little lose of transmitting power will be minimal and with the base loaded coil (if it's positioned right and the standing wave trimmed to the proper specs it will do an awesome job.
A properly tuned antenna will be the biggest key to transmitting and reception.