CB antenna and a fifth wheel

[JMartynowski]

I am shopping for a cb and antenna and was looking for some advice from the forum.



I have heard that a roof mount antenna was a good bet because of all the metal under it and it will work more better.

But I tow a fifth wheel, so how will that 8 foot parachute back there affect the antenna?



I know this can get very complicated, and I know nothing about tuning and tweaking cb's. My last (and current) cb was a radio shack with a magnetic antenna I stuck out the rear slider.

So try to keep it simple for me until I learn something.



THANKS!!!

 

[bmoeller]

Since you tow a 5er, I've heard of several people installing the antenna on the camper its self. Gets it up high.

I drive an 18 wheeler, and normally pull a bullrack. Have to run dual antennas on the tractor, to get around the trailer so I can hear behind me.

 

[Hitec.Redneck]

A mag mount on the roof will be ok, but keep in mind that the SWR's can change when you are hauling your 5th wheel. I would mount the antenna and check the swr's then connect the trailer and check it again. If they dont change to bad i would not worry about it. If they are less than 2:1 you will be ok. The lower they are the better. Hope this helps.

 

[JMartynowski]

Whats a SWR?

Single rear wheel? I have a Dually.

 

[bmoeller]

Standing Wave Ratio

Time to do some reading-

http://firestik.com/Tech_Docs.htm

 

[jjordan1]

I use the magnetic antenna on my extra tank in the bed of the truck. No problems to date.

 

[RClark]

i use a mag mt. on the acab and have no trouble with my 5th wheel.

 

[JMartynowski]

Standing Wave Ratio



Time to do some reading-



http://firestik.com/Tech_Docs.htm

THANKS!!!

Thats what I needed! I still aint to old to learn... .....

 

[OL RATLR]

THANKS!!!

Thats what I needed! I still aint to old to learn... .....

You probably will get a better reception on top than on a side mount with a

camper. That being said you should check your SWR's for maximum gain.

 

[CDonaldson]

I am running a roof mount - Wilson 1000. Put it in the roof above the center dome light because it was easy to take down the light and punch a hole, then routed the coax over to the B-pillar and down to floor, under carpet, under edge of seat area to dash and into the radio. The SWR - hardly moved, perfect match. No change in SWR with the 5er or my GN's. Great ground plane.



CD

 

[Matt42]

THANKS!!!

Thats what I needed! I still aint to old to learn... .....

Yes, but I am. Heck, I was too old in the third grade.

 

[Xgunfighter]

I have a 3' firestick on there Dodge hood mount on the drivers side. Works OK and lets me get into the garage without having to take it off. 4' was to high for garage.

 

[terrywerm]

I am running a roof mount - Wilson 1000. Put it in the roof above the center dome light because it was easy to take down the light and punch a hole, then routed the coax over to the B-pillar and down to floor, under carpet, under edge of seat area to dash and into the radio. The SWR - hardly moved, perfect match. No change in SWR with the 5er or my GN's. Great ground plane.



CD

I did the same thing, but with a K40. Don't know if it's any better than the Wilson or not, but it works well for me. It has a 90* twist feature to remove it from the roof so I can get into car washes, parking garages, etc. Give it a quarter turn and the base coil and whip come off, leaving the mount and stainless contacts on the roof. Good SWR, too. Only problem is that the whip tends to "sing" at certain speeds. I cured that by taking a 4" diameter o-ring and wrapping it on the whip in a helix shape, then glued it in place with some weather strip adhesive. The helix shape disturbs the air flow around it just enough to keep it from singing or whistling. Only problem is that people are always looking at it funny and asking what kind of antenna it is. I tell them "custom".

 

[JHardwick]

I am running a roof mount - Wilson 1000. Put it in the roof above the center dome light because it was easy to take down the light and punch a hole, then routed the coax over to the B-pillar and down to floor, under carpet, under edge of seat area to dash and into the radio. The SWR - hardly moved, perfect match. No change in SWR with the 5er or my GN's. Great ground plane.



CD

Copy that! Only thing I did different was to run the coax under the seat to a heater ... ... then a jumper to the radio, LOL.

 

[JHardwick]

I have a 3' firestick on there Dodge hood mount on the drivers side. Works OK and lets me get into the garage without having to take it off. 4' was to high for garage.

You want to be careful mounting antennas on the driver side ... ... ...



http://www.signalengineering.com/ultimate/mobile_antennas.html

 

[Ramtuf1]

I agree with the Wilson 1000. Mine is on roof and I have SWR meter in line and always have a good match with or without the 5th wheel in tow. I also can't just pull in my garage unless I unscrew the coil from the magnetic base. I think the reception I get outweighs the inconvenience of removing the coil/antenna. The higher the mast, the farther it transmits and receives.

 

[clem]

Fiberglass 5th wheel trailers do not effect the SWR that much, if you have a metal trailer you have a rear looking problem. Look at the up side if you have a metal front on the trailer it sure makes a great reflector to the front.

 

[Grizzly]

THANKS!!!

Thats what I needed! I still aint to old to learn... .....

Standing Wave Ratio, SWR, is a wave and antenna mechanics concept, by definition.

 

[JHardwick]

Standing Wave Ratio, SWR, is a wave and antenna mechanics concept, by definition.

Antennas resonate, or vibrate if you will, at a certain frequency. What you need to do is adjust the length of the antenna so that it's resonance matches that of the desired frequency. Most people set their antenna length to resonate at a frequency of 27. 185 MHz, that is the center of the CB band and also channel 19. Your SWR will be lowest on channel 19, but higher on channel 1 or channel 40.



In other words, your antenna can only resonate efficiently at 1 frequency. Transmitting on channel 1 or 40 will reflect power back into the radio, because the antenna lenght is optimum on channel 19. The power reflected back into the radio is your SWR, measured with and SWR meter.

 

[K5IP]

A good rule of thumb is to keep your antenna at least 1/4 wavelength away from any refelective surface. 1/4 wavelength at 28 Mhz is 8. 8ft so you should be close enouogh to be just fine.

Rog