Straight from the Wikipedia article about ground planes...

This is all very confusing and doesn't help you at all, however.

Think of the groundplane like this. You have a large box in the middle of a bare room. You also have a lamp. Place the lamp on top of the large box,
and you get an even broadcast of light throughout the room. Place the lamp on the floor on one side of the box, and you have an even broadcast of light on that side of the box, but a limited broadcast of light on the other sides, especially the opposite side. By placing your antenna on the top of your vehicle, you get an even broadcast and receive. By placing it on the side of your vehicle, you get a limited broadcast and receive from the opposite side.

I know it's a little hard to understand, but the best place for your antenna, all things being equal, is on top of the vehicle. This does not mean that mounting it on the side of the vehicle will ruin your reception, it just means that you won't get the 100% reception you could get.

 

Sweet. Has anyone had any problems with mounting thier antenna on thier roof? I read that you can mees up your SWR reading with too much ground plane, like the top of SUVs or Vans. Would the antenna work best dead center of the ground plane like the roof of my jeep or in front by the windshield. I appreciate the wiki link but I read that. and I understand that if I put the antenna on the drivers side I will get better reception on that side.

Most of the people that I talk to about CB's bought the stuff and mounted it where it looked cool. I don't care what it looks like. THe more I read about antenna theory the more I am starting to understand that everything needs to be in lengths of 9 feet, I need to have a good ground plane, I need an SWR meter. I was hoping we would have a CB junkie on here that had screwed around with several setups and could offer what he thinks is best. SO I'd have a place to start from and not be shooting in the Dark.......

 

I'm works great on my roof

 

Have done MANY MANY CB installations and tune ups in the last 20 years. If you mount the antenna on the left rear it will transmit from the right frone the best and visa versa (not much difference unless your coming or going) Tuning a CB is easy if you know what to look for if not dont try it yourself cause you may mess it up unless you buy a "Tune up book". There are usually VR's (variable resistors) that you can turn up for more power but cutting the Modulating clipper would give you more "Audio Swing" thus giving you more audio output... PM me with what radio you get and I'll see if I have it in my manual...Tj

 

I've run a Cobra 148Gtl for the last 25 years with a firestick and spring for a length of 102". I always mount on the left rear this keeps the whip out of the trees on the side of the road and the wind force on the whip pushes it in a clockwise direction tightening the ball on the bolt. if it's on the right side the wind force is always trying to unscrew the ball. With a stock legal radio, 4 watts output and 80% mod. and good antenna system you should be able to talk 10 - 15 miles line of sight, but most radios of of the box usually are only putting out 2-3 watts and 60% mod.

 

i'm interested in how to correctly tune a cb also. i've been running a cobra NW 29 LTD for 5 years or so in my trucks w/ 2ft roof mount magnet antenna & had good short range reception on the trails i run.

put it in the jeep last week & the rigs behind me on the trail were distorted horribly. i came in clear on everyone elses, but they all sounded like they were miles away on mine.

 

hells yeah I will.....

 

I know that if you run duals then you project and receive farther to the front and back. Here's something I found.

http://www.firestik.com/Tech_Docs/63Things.htm

It answered alot of questions......

ANYONE GOT ANYTHING TO ADD PLEASE POST IT!!!!!!!

 

I have a Cobra 19 citizen cb and no antenna?
What kind and where should i place it?

 

Well, first of all, that's a good article with lots of useful info you lined to. GOOD FIND!!!


As far as the single vs. dual antenna question, I vote single. Yes, with a dual you will probably get a slight gain in front and rear send receive, but actually at the expense of loss of side to side. So unless your certain that everyone you will want to talk to is either behind or in front of you, all the extra cabling, cost and installation just isn't worth it. One of the reason's most people assume 2 is better than one is because they see one on each side mirror on 18 Wheelers. The reason for that however, is because the majority of trucks carry 13'6" High enclosed trailers so they need one on both sides to help compensate for signal blockage of trailer and since the Federal Guideline for bridge height on federally funded roadways is, I believe, 13' 9", it would be impossible to mount a single antenna on a truck tall enough to reach over trailer and not hit overpasses.

Link to a good webpage that helps explain benefit/disadvantage of dual instead of single antenna.
http://www.cosjwt.com/index.php?a=20


If you decide to still use duals though, just make sure they are matched pairs and use 75 ohm cable of same length from each one to transceiver. As the link above states, also try to keep distance between antennas UNDER 9'. Also, the antenna is the most important part of the system, so try and get the best one you can afford.

I personally prefer masts or coils over the fiberglass sticks, but up to you and your budget. I would personally recommend a Predator 10K(w 17" shaft & single coil & mounted to rear bumper), MonkeyMaid(mounted to rear bumper), Wilson's(mount dependent on model) or the time-tested standard 102" stainless whip(mounted to rear bumper) if run single. If determined to run duals though, I would go with Firesticks or Wilsons, Just make sure they clear top of vehicle by at least a foot, 2 if possible, if not mounted to top of vehicle and make sure to stay away from low branches if do mount to top. whichever you chose, make sure to get SWR set properly.

Link to a webpage I found that sells mentioned antennas.
http://www.cbcity.com/category/Antennas-32/rec/48


As for using an SWR meter to tune CB, see if this helps:

The SWR meter needs to be placed in line between the antenna and the CB. Connect the antenna (normally connected to the back of the CB ) to the connector marked "Antenna" or "Ant" on your SWR Meter. Connect one end of the short jumper coax to the "transmit" or "Xmit" on the SWR meter. Connect the other end of your jumper coax to the CB.

Assuming you have a standard SWR meter the switches should read as follows: REF or SWR, FWD, and there should be a slide switch marked "set" or "Adjust". If different consult your meter's owners manual.

With the radio on the lowest channel (1 on CB) and the SWR meters switch in the Forward (FWD) position, depress the transmit switch (key up) located on the microphone. While holding the unit in this transmit mode, adjust the meter needle to the set position using the Set or Adjust **** on the meter. As soon as the needle is in alignment with the corresponding mark on the meter face, flip the switch to the Reference (REF) position. The meter is now showing your SWR on channel one. Note the value and quickly release the microphone switch. Record this reading.

Repeat the previous step on channels 19 and 40.

How to read your results: If SWR on channels 1, 19 & 40 is below 2.0(this to me is absolute max and would be advisable to get below 1.5, the lower the better(perfect is 1.1)), your radio can be operated safely.

If SWR on all channels is above 2.0 but not in the "red zone" (normally over 3.0), you may be experiencing coaxial cable reaction (bad quality, wrong length, etc.), insufficient ground plane, or have an ungrounded antenna mount.

If SWR is in the "red zone" on all channels, you probably have an electrical short in your coax connectors, or your mounting stud was installed incorrectly and is shorted. Do not operate your radio until the problem is found, serious damage can occur to your radio.

If SWR on the lowest channel is higher than it is on the highest channel, your antenna system appears to be electrically short. Your antenna length may need to be increased.

If the SWR on channel 40 is greater than that on channel 1, your antenna is considered to be "LONG" and reduction of physical height and/or conductor length will correct this situation.

GOOD LUCK FROM A TRUCK DRIVER!!!

 

Well, first of all, that's a pretty good article with a lot of useful info you linked to. GOOD FIND!!!


As far as the single vs. dual antenna question, I vote single. Yes, with a dual you will probably get a slight gain in front and rear send receive, but actually at the expense of loss of side to side. So unless your certain that everyone you will want to talk to is either behind or in front of you, all the extra cabling, cost and installation just isn't worth it. One of the reason's most people assume 2 is better than one is because they see one on each side mirror on 18 Wheelers. The reason for that however, is because the majority of trucks carry 13'6" High enclosed trailers so they need one on both sides to help compensate for signal blockage of trailer and since the Federal Guideline for bridge height on federally funded roadways is, I believe, 13' 9", it would be impossible to mount a single antenna on a truck tall enough to reach over trailer and not hit overpasses.

Link to a good webpage that helps explain benefit/disadvantage of dual instead of single antenna.
http://www.cosjwt.com/index.php?a=20


If you decide to still use duals though, just make sure they are matched pairs and use 75 ohm cable of same length from each one to transceiver. As the link above states, also try to keep distance between antennas UNDER 9'. Also, the antenna is the most important part of the system, so try and get the best one you can afford.

I personally prefer masts or coils over the fiberglass sticks, but up to you and your budget. I would personally recommend a Predator 10K(w 17" shaft & single coil & mounted to rear bumper), MonkeyMaid(mounted to rear bumper), Wilson's(mount dependent on model) or the time-tested standard 102" stainless whip(mounted to rear bumper) if run single. If determined to run duals though, I would go with Firesticks or Wilsons, Just make sure they clear top of vehicle by at least a foot, 2 if possible, if not mounted to top of vehicle and make sure to stay away from low branches if do mount to top. whichever you chose, make sure to get SWR set properly.

Link to a webpage I found that sells mentioned antennas.
http://www.cbcity.com/category/Antennas-32/rec/48


As for using an SWR meter to tune CB, see if this helps:

The SWR meter needs to be placed in line between the antenna and the CB. Connect the antenna (normally connected to the back of the CB ) to the connector marked "Antenna" or "Ant" on your SWR Meter. Connect one end of the short jumper coax to the "transmit" or "Xmit" on the SWR meter. Connect the other end of your jumper coax to the CB.

Assuming you have a standard SWR meter the switches should read as follows: REF or SWR, FWD, and there should be a slide switch marked "set" or "Adjust". If different consult your meter's owners manual.

With the radio on the lowest channel (1 on CB) and the SWR meters switch in the Forward (FWD) position, depress the transmit switch (key up) located on the microphone. While holding the unit in this transmit mode, adjust the meter needle to the set position using the Set or Adjust **** on the meter. As soon as the needle is in alignment with the corresponding mark on the meter face, flip the switch to the Reference (REF) position. The meter is now showing your SWR on channel one. Note the value and quickly release the microphone switch. Record this reading.

Repeat the previous step on channels 19 and 40.

How to read your results: If SWR on channels 1, 19 & 40 is below 2.0(this to me is absolute max and would be advisable to get below 1.5, the lower the better(perfect is 1.1)), your radio can be operated safely.

If SWR on all channels is above 2.0 but not in the "red zone" (normally over 3.0), you may be experiencing coaxial cable reaction (bad quality, wrong length, etc.), insufficient ground plane, or have an ungrounded antenna mount.

If SWR is in the "red zone" on all channels, you probably have an electrical short in your coax connectors, or your mounting stud was installed incorrectly and is shorted. Do not operate your radio until the problem is found, serious damage can occur to your radio.

If SWR on the lowest channel is higher than it is on the highest channel, your antenna system appears to be electrically short. Your antenna length may need to be increased.

If the SWR on channel 40 is greater than that on channel 1, your antenna is considered to be "LONG" and reduction of physical height and/or conductor length will correct this situation.

GOOD LUCK FROM A TRUCK DRIVER!!!

 

I would try and get the best antenna I could afford to help that little radio get best performance possible.

***Just a note in case anyone decides to mount antenna to rear hatch and doesn't notice, rear hatches on XJ's are fiberglass so you will need to run a ground strap to frame or other good metal surface.


ALSO, SORRY ABOUT PREVIOUS DOUBLE POST!
I'm on a poorly designed service line with multiple computers online at times and I thought page had hung so stopped and resent but guess first attempt had already posted before I stopped it. MY BADD!!!!

 

Not likely in real world situation. With a basic 4 watt CB, you'd be lucky if could SEND 4-5 miles and that's across flat ground and no obstructions, which unless your in the ocean on a boat or in the desert, isn't likely. Possible to receive from that far from someone broadcasting from a larger radio, but not receive in my experience. I had a Connex 4600 Turbo(which was bench-tested throwing 208 watts) in my big rig with a Predator antenna and on a good day I could get out 20-25 miles MAX on fairly flat highway.

IF YOU DID THOUGH, I"D KEEP THAT SETUP 'TIL IT DIES BEYOND REPAIR IF I WAS YOU!!! LOL

 

I wouldn't do it if it were me. But just my opinion.

'Swing' performance increase is highly over-rated. Can only bump up to double it's base output max, and at the expense of distortion. Not worth it in my book. If really want/need more output, get a bigger radio or if possible have a good CB shop install larger finals in the one you already have and/or get a better antenna.

See this article and scan down to #'s 4 & 5 to read a good detailed explanation of swing and how it works.
http://www.shadowstorm.com/cb/CB_Myths_Exploded.html

 

OH YEAH!!!!! Keep postin!!!!!!

Anyone got a rig on their jeep they are using and wanna let us know how far it reaches. Make sure to include antenna type and mount location along with what CB your using......