Mag mount high swr

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Huntingdeer24

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I got a cheep eBay antenna a few mounts ago it has high swr.it is not tunable. It's at 3:5.i unscrewed it and tested it with the antenna off same thing.could I have a bad connection somewhere? It's a 2m antenna.
 

k6cpo

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What do you have it sitting on? Those antennas need a metal ground plane under them to operate properly.
 

dksac2

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If there are no adjustments for the length of the whip and you are sure the antenna is attached to a good metal surface, it's most likely a bad antenna. You might try putting a new fitting on the end of the coax.
Many people are reluctant to drill a hole in the top of their vehicle, but an antenna mounted directly to the vehicle will always work better than a mag mount.
If it's a newer vehicle, you have to watch out for air bags and other electronics.
73's John KF7VXA
 

k6cpo

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My truck roof then my metal bed post.
More questions:

  1. What frequency is the antenna designed for?
  2. Are you checking the SWR on the frequency the antenna is cut for?
  3. What are you using to test the SWR?
The other person is correct in that an antenna mounted directly to the roof of a vehicle is always better than a mag mount. I started with a mag mount antenna, but changed over to an NMO mount later on. I had no qualms about drilling a hole in the roof of the truck, but then my truck is 15 years old and I plan on keeping it until it dies. The nice thing is that the NMO is a screw mount and I can change antennas at will. I also remove the antenna when I park the vehicle overnight and I have a cap to cover the mount when I don't have an antenna installed.
 

robertmac

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Cheap could be your problem. Buy a decent antenna. Lots of reviews on eham.net.
 

teufler

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if you have an ohm meter, take the antenna off, unscrew the coax from the radio. Check continuity from the cener conductor to the antenna shield. It should show open. If its closed, your coax is shorted. Not you faultm, just got installed wrong. You can cut the connector off and install a new one.Its possible the center conductor is shorted ouit in the mag base. There are adjustments that you can loosen, then reposition and tighten.
 

dksac2

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If you are looking for a new antenna, and plan on other radio's in the future, The Comet CA-2 X 4 SR is a wide band antenna that will work with the Amateur VHF/UHF frequency's as well as GMRS.
It has decent gain and good SWR with either Amateur VHF/UHF or GMRS.
I use the Comet the majority of the time, but also carry a Larson 1/4 wave that I can switch to when I want a lower profile antenna or are near the mountains or repeaters up a lot higher than a valley floor.
The Comet is a heavy antenna, that does fold over, so it really should be mounted to an NMO fixed mount.
If your just looking for a 2 meter antenna, you'll never go wrong with a Larson. They make a 1/4 wave and 5/8 wave antenna. They are light and are some of the best on the market, the 5/8 wave will have gain.
One other thing to consider. If you live in a hilly area, sometimes the best antenna is a 1/4 wave. If it's a flatter area, than an antenna such as the 5/8 wave Larson or the Comet would be a good choice.
Unless it's a brand new car that you plan on reselling quickly, a hole in the roof will make no difference when you go to sell your vehicle, just buy a plastic cap to go in the hole in the roof when you remove the NMO mount.
If the car is newer, it's many times best to go to a radio shop and pay to have it installed properly. An older vehicle without airbags, just remove the headliner so you can find the best place to drill the hole, remove paint from the inside so the NMO mount can get good metal to metal contact.
An antenna mounted directly to the vehicle will do quite a bit better than a mag mount and you can usually get lower SWR also.
The antenna is the heart of any radio system, going cheap is a sure way to disappointment.
Also, use nothing less than 8 Ga. wire from your battery to the radio. A lot of voltage is lost in wire.
Be sure to use a grommet where the wire goes through the firewall and fuse the wire at the battery.

73's John KF7VXA
 

teufler

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I have a signal analyzer by mjf, a Telewave Swr meter and a cheap swr meter made for vhf and uhf. You will need som,e meter that measures vhf frequencies to measure swr or borrow a signal analyzer. Generally the antenna is precut at the factory and just measuring with a tapoe measure to follow the specs gets very good results. Your antenna, doesn't it have an allan screw that holds the antenna that can be losened and adjusted.? You will then need bolt cutters to safety cut the stinger, if the range of adjustment does not allow enough movement.
 

N8IAA

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Since no one asked, what is the length of the whip? 19"? 6"?
You're not going to be able to use a CB SWR/Watt meter to test the SWR. I'm presuming that's what you used. You will need, as mentioned in another post, a SWR/Watt meter that measures in the VHF/UHF ham frequencies.
Let us know.
Larry
 

teufler

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I hate to throw anything away but as you mentioned earlier, it might be better to get another antenna . There are several, then get a good mag mount and forget your troubles .
 
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