Need a little help.

[trkntrlrman]

I'm installing a cobra 29 wx nw st CB in my Travil trailer. where I also have my BCD996 Mobile installed. I have the Scanner antenna mounted on a 15' PVC pipe mounted to the sine of the slideout which is about half way on a 27' tailer. My question is 1. How far from the scanner antenna should I mount the CB Antenna, and 2. what can I do to get a good Ground plane as the trailer roof is a rubber roof over wood. The only Aluminum is on the side walls. I don't want to Key up and fry the scanner. My other concern is cable length. There is a roof rack I can mount to on the roof to the rear, about about 10 feet from the scanner antenna. My other thought was that maybe I could mount it to the top of the TV antenna which is a crank up antenna that would allow putting it down during travil . The antenna is a 48" single truckers antenna. Will the extralong cable effect the transmition or reception of the CB? Should the CB antenna be Higher or Lower than the Scanner antenna?
I tried to get som help from the local Radio Shack but they are useless anymore. no one there has a clue. I'm in the Palm Springs area, and there is nothing around here...
Thanks for the help It's greatly appreciated...

 

[LtDoc]

How far away? As far as possible AND practical. There will be some interaction, the closer the more interaction so keep that in mind. You'll have to tune that antenna anyway, so in most cases that'll take care of most of that interaction.
The best advice about not burning up that scanner is to not have it programmed for any of the CB frequencies. Or, if you want to listen to CB with that scanner, then turn it off when the CB radio is on. Making the metal siding a part of the CB antenna isn't going to burn up that scanner (keep the no CB freqs in mind though).
Will the length of the feed line affect things? It can, but with the typical lengths used (less than 50 - 100 feet?) the 'affect' isn't going to be huge in either direction.
No "groundplane"? Well, the simplest solution is to add one. That "groundplane" is the 'other half' of the antenna. If it isn't there, or isn't very 'good', then neither will be the performance of that antenna. That 'other half' can be almost anything conductive, from a nine foot length of wire to multiples of that wire, to copper or aluminum or steel plating the top of your trailer. Longer than necessary very seldom hurts.
Being able to 'drop' that antenna while moving is certainly a nice thing to be able to do. There are a number of ways to do that, pick the one that's 'best' for you. Putting that antenna on a TV antenna is going to affect both, so that would be one'a them try it and see thingys.
All antennas benefit from being higher. How high you can get the thing is dependent on your circumstances. Do what you can and then quit worrying about it.
You can make almost anything 'work' if you have to. That doesn't mean it will work well, but it will certainly beat not having an antenna at all.
Good luck.
- 'Doc

 

[trkntrlrman]

Thanks Doc. So if I understand you correctly the ground plane doesn't have to be a solid piece of metal like a car roof etc; it can be a wire? If this is the case does the size , or the Area if the ground plane effect the distance of operation of the CB? I know that if you mount in the center of a car roof vers the back of the roof, it changes the direction of opperation. I also have a metal shed behind me where I could mount the antenna, would the angle of the roof be a problem or does the ground plane have to be 90 deg. to the antenna???
Sorry, just trying to learn..

 

[LtDoc]

That wire will work just like the roof of a car. It won't make any difference as far as 'range' is concerned, but can make a difference in the shape of the radiation pattern. If you can put two wires 180 degrees apart, it will keep the shape of the radiation pattern symmetrical, it won't be 'directional'. Even with just one wire, the thing isn't going to be very directional anyway. I can't/won't make any guesses about the mechanical aspects of it but a strip of metal flashing laid from one end/corner of that trailer to the opposite end/corner would probably work just dandy. Nail or glue the thing down so it doesn't flop around. That brings up how you'd mount that antenna on a rubber covered wood roof? Tht's another one of those mechanical thingys and I hope you know more about that than I do (never done one like that).
Rather mount the antenna on that metal shed? Have at it, ought'a work just fine. I'd put it at the highest point, the ridge of that roof, not on one side or the other. Keeps things symmetrical. Should work as well as if it were on a car.
- 'Doc

 

[trkntrlrman]

Thanks Doc, I'm going to try mounting the antenna on the roof rack, I'm going to use some 1/2 " aluminum Tubing and mount the Antenna on a plate mounted in the center of the 4 pipes. Will the hollow tubing be a problem??the center plate will probably be about 6"x6" depending on what i can find. Maybe 12x12. Mounting the pipe to the rail should make is pretty solid. I'll have to look for a fold down mount for travel. I always wondered what i was going to use the rack for..hehehheh and yes the scanner will have those freqs turned off...