Alright, I've got a 102" steel whip mounted onto a horizontal light bar (also holding four 100 watt floodlights) which is mounted onto a chrome roll bar which is mounted in the bed of my truck. Knowing that the bed is made out of that plastic material, I grounded (with solid copper wire) the roll bar to the chassis, and then I ran a ground wire from the light bar and coax connector to the chassis, without the antenna or hot line of the coax being grounded. The radio I'm currently using is a Connex 4600 Turbo, which is also grounded well. I've made sure there's no paint or anything keeping me from getting a good ground too. I'm using just enough coax needed from the antenna to the radio, but I have tried one 18' line as well, just to check. My problem is my external meter is showing I've got a standing wave of at least 2. I'd love to have it down around 1.4 or lower. I was previously using a Superstar 121, which also was giving me a SWR of 2-3. I've tried just about everything I can think of. I've covered up the roll bar and lights from causing a high SWR, I've tried different antennas and different lines too. The base of the antenna is even with the top of my truck, and there's nothing else around to interfere with the signal. Is there some interference from the truck's computer system or something else I haven't thought of? Thanks.
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High SWR
- Thread starter Bonekrushur
- Start date
What is the distance between the two whips?
Have you tried using just one antenna?
Did you check the connections and ground with an Ohm meter?
Are you using a 75 ohm coax/co-phase harness between the two antennas?
I think that it will look cool with 2 whips.
But in truth - it will work much better with just one whip. You don't have them at least 1/4 wave length/8 ft apart! If the antennas aren't precisely in the right position/distance from each other/"phase"; you will have phasing problems. If you aren't using a 75 Ohm cophase harness - and the whips aren't exactly in proper phase; it will be more trouble than it is worth - IMO. One whip will work OUTSTANDING as it is!
http://www.bellscb.com/cb_radio_hobby/antennas/antarray.html
If you decide that you are going to go with just one antenna and bypass the grief of making two work; you might see a 1.5 to 1 SWR. At this point, I would trim the top of the whip in 1/4 inch bites until the SWR is where you want it - for the range you need. Better still; I would have a friend check it with his MFJ-259B antenna analyzer and use it to trim the antenna for the best resonance that you will most likely use the most often. This might also give you a real flat 1.1 to 1 SWR if everything else is done correctly...
Have you tried using just one antenna?
Did you check the connections and ground with an Ohm meter?
Are you using a 75 ohm coax/co-phase harness between the two antennas?
I think that it will look cool with 2 whips.
But in truth - it will work much better with just one whip. You don't have them at least 1/4 wave length/8 ft apart! If the antennas aren't precisely in the right position/distance from each other/"phase"; you will have phasing problems. If you aren't using a 75 Ohm cophase harness - and the whips aren't exactly in proper phase; it will be more trouble than it is worth - IMO. One whip will work OUTSTANDING as it is!
http://www.bellscb.com/cb_radio_hobby/antennas/antarray.html
If you decide that you are going to go with just one antenna and bypass the grief of making two work; you might see a 1.5 to 1 SWR. At this point, I would trim the top of the whip in 1/4 inch bites until the SWR is where you want it - for the range you need. Better still; I would have a friend check it with his MFJ-259B antenna analyzer and use it to trim the antenna for the best resonance that you will most likely use the most often. This might also give you a real flat 1.1 to 1 SWR if everything else is done correctly...
I've tried tuning it with no luck. I'm currently using a 5000 watt Astatic meter. Sorry if I wasn't clear, but I am using just one steel whip. I grabbed another one off another truck of mine and tried it, since I know the CB setup on that truck has a low SWR. The meter should be fine, it shows good on my base setup as well. I've got an 18' line which I'm going to use to hook up my mobile radio to my base antenna. I'll run this line from my radio to the meter in the house, then keep the line already running from the base antenna to the meter inside. That way I can check to make sure my radio is working properly.
Yes, the base of the antenna comes down in between them. Two on the left, two on the right. I did lay a few thick rubber mats over top of the lights to see if it would help, but it didn't.
That doesn't count as insulation, as one might think. The antenna needs to be above them if they are really close to the antenna...
Well, it certainly might be the problem, or at least part of it. Now I can say that all of the antenna (except maybe an inch or two of the bottom) is above the lights. Just about 100 inches straight up into the open air. Still, I thought the signal may be radiating down and bouncing off the lights in a bad way, causing the SWR to be high. That's one reason I want to check the radio and narrow my focus only to the antenna. I really do think that is where I'm having trouble.
Keep us posted in what you find.
It just might help someone else in a similar circumstance.
Personally, I would remove the two inner lights closest to the antenna - and just try it with the two outer lights.
Just a thought...
EDIT: The antenna whip itself should be 102 inches; is it already too short?
It just might help someone else in a similar circumstance.
Personally, I would remove the two inner lights closest to the antenna - and just try it with the two outer lights.
Just a thought...
EDIT: The antenna whip itself should be 102 inches; is it already too short?
Well, I haven't measured its exact length, but I haven't done anything to it since I bought it new.
Then it should be OK...
Most 1/4 wave steel whips came in 102" lengths.
Are you using a 6" spring mount too? These will bring it up to 108 " in length. An antenna analyzer will tell you at what point it is most resonant at; and that will tell you if it is too long or too short for your desired frequency...
Yes, I have the spring mount on it. I was also thinking, and it might be hard to explain here, but where the stud runs up and screws into the bottom of the spring, there is a plastic washer insulating the outside of the spring from grounding out on the light bar. Now in between that washer and where the stud comes from, it runs through a hole in the light bar. Now I have made sure that stud isn't touching anything else so the antenna won't be grounded, and the hole it runs through isn't too small or too big, but it's not (light bar) the normal aluminum a lot of springs are mounted to. That light bar is made of solid steel, and I wonder if any of my signal is radiating and bouncing off that steel from the stud, giving me a high SWR.
If the ball mount assembly is correctly assembled that the spring and the whip are attached to; then that shouldn't be a problem.