I have a simple fiberglass whip, about 4' long, mounted on a Radio Trash / Sack / Shack ball mount and spring drilled thru the rear passenger side corner of the Jeep. I know this is drilling a hole, but it is a clean setup, with the coax protected, and not having to fish it through somewhere.
SWR is difficult to tune with the fiberglass antennas. I have also had good luck with a base loaded metal whip of the radio-shack variety. These are the ones with a coil at the bottom. These are easier to tune for your SWR, as the main whip part can be moved up or down with a small allen screw. A 102" steel whip is nice, but it's a PITA on a tight trail with trees - this is where it hits people flying around - I can't see using one on a trail Jeep.
I'm a mechanical guy, but here is how I understand it:
As was described, SWR is your standing wave ratio. It is the ratio of "power sent out by the radio" divided by the "power that is radiated by the antenna". Ideally, you want this to be 1:1. As in, all of the power sent out by the radio is radiated by the antenna. This is seldom the case. Antennas are set up for a certain frequency. If your radio goes from 26.965 Mhz (channel 1) to 27.405 Mhz., (channel 40), your antenna needs to be tuned to work somewhat OK on all these frequnecies. You will get the best signal out with a 1:1 "match", or SWR. Usually, I try to get this on channel 20, and then it will drift a little on 40 or 1. You would like to see the match below 1.5:1 at all times. If it gets over 3:1 your radio can be damaged, as the power it is sending out is not getting radiated by the antenna, and is going right back into the radio, supposedly, heating it up and causing bad things. As you go further away from 1:1, your output signal drops.
Basically, an SWR meter can be had a Radio Shack, and you connect it between the radio and the antenna. Set it on "set" or "Ref." (there is a switch on it that usually says "Set" or "Ref." on one side, and "Forward" or something like that on the other.). Key the mic with the meter on set, and line it up to a ref mark on the meter. Then, switch it over to the other way, and key the mic again. 1:1 is usually where the needle doesn't move, and it will go up to whatever your match is.
From a ground-plane standpoint, the position of your antenna can matter on your signal propogation. A van has a great advantage here. An antenna in the middle of the roof on a van will propogate the signal good in all directions. Mine, at the rear passenger side of the Jeep, gets out good to the front and the left, but not so well to the rear or the right. If you put it say on your spare tire carrier dead center, you would get out good to the front, but lousy to the back.
Not sure all of this is spot-on, but it is my understanding
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