Well then I reckon it's fine. I've also checked the coax for shorts, but everything looked good there. I'll just try these other ideas later today and hopefully I can say it's fixed tonight.
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High SWR
- Thread starter Bonekrushur
- Start date
It doesn't sound like you've done any tuning of that antenna, which could certainly result in not having a very good SWR.
Any and everything around an antenna will affect it. That doesn't mean that there will be a huge adverse affect, but there will be some, which is entirely normal. Considering how/where you are mounting that antenna, I don't think I'd worry a lot about the lights, etc, tuning can compensate for that.
All antennas require some tuning, none of them are just right straight out of the 'box'. Checking SWR at the top and bottom ends of the band, and in the center, can give you an indication of whether that antenna needs to be lengthened or shortened. An antenna analyzer is very handy to have for that sort of thing, but not too many people have one handy. So, you're stuck with using just an SWR meter which can indicate only one thing about an antenna, not the most important thing either.
I think you are correct in thinking that the antenna is the 'problem', I seriously doubt if your radio is.
- 'Doc
Any and everything around an antenna will affect it. That doesn't mean that there will be a huge adverse affect, but there will be some, which is entirely normal. Considering how/where you are mounting that antenna, I don't think I'd worry a lot about the lights, etc, tuning can compensate for that.
All antennas require some tuning, none of them are just right straight out of the 'box'. Checking SWR at the top and bottom ends of the band, and in the center, can give you an indication of whether that antenna needs to be lengthened or shortened. An antenna analyzer is very handy to have for that sort of thing, but not too many people have one handy. So, you're stuck with using just an SWR meter which can indicate only one thing about an antenna, not the most important thing either.
I think you are correct in thinking that the antenna is the 'problem', I seriously doubt if your radio is.
- 'Doc
If his antenna is not seeing a sufficient ground plane then it's seeing the coax as it's ground plane and may require either lengthening the antenna or the coax to stop the transformer effect of the coax shielding.
I had the same problem on my 70 chevy when mounting my predator 10-k at the right rear corner of the bed and that was my solution and only then could I tune the antenna.
I had the same problem on my 70 chevy when mounting my predator 10-k at the right rear corner of the bed and that was my solution and only then could I tune the antenna.
post a pic from the tailgate then up close of the antenna mounting
its real hard to diagnose a problem when the antenna could be bent over attached to the tailgate and inside a garage or something
its real hard to diagnose a problem when the antenna could be bent over attached to the tailgate and inside a garage or something
DOC was on the right track with the SWR test`s
Please check the SWR on Channel, 1 then 20 then 40 and post the result here.
From what you have posted it seems you have the grounding covered You may need to remove the Spring and try mounting the antenna right on the mount.
A Simple Old rule of thumb
Longer=Lower
Shorter=Higher
A longer antenna will resonate at a lower frequency
A Shorter antenna will resonate at a higher frequency
If your SWR results are:
Best on Ch 1, a little worse on CH 20 and worse on CH 40 your antenna is on the long side and needs to be shorter
If your SWR results are:
Best on Ch 40, A little worse on CH 20 and the worst on CH 1, the antenna is on the short side and needs to be longer
As you are running an "export radio" you can do the same test one band down and one band up to show the result over a larger frequency range.
There are scenarios where your lowest SWR will be around CH 20 and It seems no matter what you do you can not change them, this requires more thought, but try to work your way thorough it step by step as you have been doing.
A 1/4 wave whip sometimes will not show a good match without the proper ground as Mack has said, If you think about it, most 1/4 wave ground planes use sloping radials, this is to help match the feed point @ 50 ohms.
For now, Let us know the result of the SWR test.
73
Jeff
Please check the SWR on Channel, 1 then 20 then 40 and post the result here.
From what you have posted it seems you have the grounding covered You may need to remove the Spring and try mounting the antenna right on the mount.
A Simple Old rule of thumb
Longer=Lower
Shorter=Higher
A longer antenna will resonate at a lower frequency
A Shorter antenna will resonate at a higher frequency
If your SWR results are:
Best on Ch 1, a little worse on CH 20 and worse on CH 40 your antenna is on the long side and needs to be shorter
If your SWR results are:
Best on Ch 40, A little worse on CH 20 and the worst on CH 1, the antenna is on the short side and needs to be longer
As you are running an "export radio" you can do the same test one band down and one band up to show the result over a larger frequency range.
There are scenarios where your lowest SWR will be around CH 20 and It seems no matter what you do you can not change them, this requires more thought, but try to work your way thorough it step by step as you have been doing.
A 1/4 wave whip sometimes will not show a good match without the proper ground as Mack has said, If you think about it, most 1/4 wave ground planes use sloping radials, this is to help match the feed point @ 50 ohms.
For now, Let us know the result of the SWR test.
73
Jeff
Well I know I'm having a problem with this antenna and the way it's working with this truck. The SWR is exactly 2 on every channel, regular band. My whip doesn't have any set screws in it, so I can't adjust it up or down, and I shouldn't have to be cutting it any. My truck's bed isn't metal, it's some type of hard thick plastic material, obviously cheaper. I guess that's what Toyota is using in the new Tacomas, but I was wondering if because the whole bed is plastic, it may be affecting the way the antenna is radiating. My roll bar is mounted in the bed, bolted down in the bottom of the bed near the cab, and bolted down on the two wheel well rises in the bed.
This is why I pointed out that having an antenna analyzer would be best to have, rent, or borrow. It will be able to determine where the resonant frequency is - and how far off it is from where you will be operating it. At this point if it is off in a adjacent freq; then the antenna may well need to be trimmed a little until resonance and SWR are where you need them to be.
You can use an SWR meter to find out where it has its best tune. If the SWR is real low on 27.555mhz; then the antenna is too short. I doubt that is the case. If the SWR is real low on 26.400mhz; then the antenna is too long. I suspect that to be the case.
TO recap: you should just look for a frequency that gets the lowest SWR - whatever it may be. If it is lower on 26mhz and below; it is too long. If SWR is real low at 27mhz and above it is too short.
Read: http://www.bellscb.com/cb_radio_hobby/swr.html
The frame and the roll bar provide more than enough metal to support a proper metal ground plane. So long as the roll bar is grounded to the frame - this shouldn't be the issue nor the problem.
What did you do with the lights?
I hate to ask the dumb question, but your swr is a flat two to one all the way across the band??? Never seen that before, but if that is all the higher it is, and you can't get better, I really wouldn't worry about it too much, as that is still not terrible, and will work fine.
Ok, then try the same thing a band up and a band down, And post what you get. Or even 2 bands down and 2 bands up, a 1/4 wave is going to be broad banded.
Just for Grins, have you tried to mount just the whip (remove the spring) and check SWR and report the findings.
Your explanation of how the spring is mounted sounds fine, the top portion should be insulated from touching the metal of the light bar. The bottom should be making good contact with the metal, as this completes the ground.
73
Jeff
( On Edit:
I went back a re read you post at the beginning, I would change the solid copper wire used to ground the roll bar/light bar to copper braid, or at very least stranded copper wire, with the truck bouncing around the solid copper is prone to breakage because it will not flex....also a braided ground will provide a much lower resistance to RF that a smaller conductor)
2:1 can be used at lower power levels, most export radios can run into that all day with no problem, but take your time and see if it can come down. If you had an antenna analyzer it would be great, but you can accomplish a lot with a good SWR meter, don`t get frustrated.)
I did take off the spring and try without luck. In fact, I've tried several different types of antennas, not just the steel whip. I've taken the lights off the bar and tried, but it didn't work. I've ran another ground wire with stranded line, instead of solid as well. To be more exact, my standing wave does fluctuate from 1 to 40, but only from about 1.8 to 2.1, and it's the same at 1 and 40. I'll have to get my hands on one of them analyzers, maybe Muscleman has one over here down the road. I'll have to check the SWR again on the other bands, but if I remember right, I think it was lower on C and higher on E, with D being regular. When I hooked my base antenna into the radio today that SWR dropped flat-just what I'm looking, except on my antenna.
Removing the spring should have changed the tuning on that antenna VASTLY. That would be like trimming a whole 6 inches off the entire length. It is fair to say that something else is amiss.
Are you using a different piece of coax to it from the base radio?
Is all of the antenna whip/base above the roof line?
Is the coax used in the truck 75 ohms - or 50 ohm?
Is the mobile radio hooked to the battery - and grounded to the frame as well?
I would also re-check the ball mount for the whip - to be sure that all of the insulators are present and in the right place too.
All of it is above the roof line. The coax I'm using on the truck now is RG-8X, so it's 50 ohms, and what I used to the base antenna was RG-213, so I tried substituting RG-213 on my truck and it didn't change anything. I have my hot line from my radio run to the positive post of my battery, and my negative cable runs to the truck frame. I did check the mount location again, but it's set right.
Guess it's time to try a different radio in the pickup and or jumper from the radio to the meter to see if either has a fault. You've already proven the meter is most likely not the problem.
I think he said that he had a SS 121 in there and it acted the same, so I doubt it is the radio.
As the Coax has been changed, that seems to rule that out. You can try subbing a different jumper in front of the meter, and see what the result is.
I am curious where the 1.8 reading is at, and why removing the spring apparently had no effect.
I am also interested in what the SWR is at the Lowest band, channel one.
1:8 is not the worst SWR in the world, but it should be better.....have you used this Radio Setup to talk to anyone, and what are the results?
How does it compare to your other truck...
73
Jeff