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SWR Problems


Chanceseiler
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Hi everyone

 

I am new to GMRS but old CB'er. I put in a Midland radio in my truck. ( It's a recycled beer can truck )

So a mag mount will not work. The cheep little antenna mag mount gives me a 1 1.2 swr. The ghost antenna gives me

a very high swr. 1:2.5 with RG8X. Does coax type matter?  There is no shorts is the coax. Any help would be 

greatly appreciated. I'm about to walk away from GMRS.

P.S. radio in Side X Side is same setup, but RG58 NMO mount from Midland. SWR 1:1.3.

Thank you

Chance

WRJT366

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Not sure why you would walk away from GMRS just because you are having a technical issue. Technical issues can and do exist everywhere in radio. All issues are just problems waiting to be solved. The hobby of radio is all about the journey of learning.

 

SWR issues can be caused by many things. Bad cable, connector, or adapter. Improper tuning of antenna. Antenna design expecting a ground plane but does not have one. Incorrect antenna being used. Antenna is too close to a reflecting surface when a reflector is not (by design) expected. A defective antenna. Others as well.

 

I don’t know beer trucks so I cannot relate to why a mag-mount cannot be used. Perhaps some pictures would educate me and others.

 

Could you post pictures and more information about the antennas your using, where and how you are mounting them?

 

With good product properly installed you should be able to achieve mobile SWR numbers mid to low 1.[n]:1 range.

 

Feed us with more information and I am sure the solution will emerge.

 

Michael

WRHS965

KE8PLM

 

 

Sent from my iPad using Tapatalk

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Micheal

 

 I have a 2017 F-150 aluminum body. Took the paint off the inside of the roof to make sure ground was good. Checked coax to make sure my solder work was good. Coax is 19.5' long.

I could get away with half of that. Coax is only 1 years old & never used before. I am useing the Midland 3 dB gain gost antenna. I was sent two bad Midland 6 meter antenna cables (made by Midland) and both was defective. That's when I ordered NMO mounts from The antenna farm. That way I could use the RG8X. 

Chance

WRJT366

   
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Micheal

 

 I have a 2017 F-150 aluminum body. Took the paint off the inside of the roof to make sure ground was good. Checked coax to make sure my solder work was good. Coax is 19.5' long.

I could get away with half of that. Coax is only 1 years old & never used before. I am useing the Midland 3 dB gain gost antenna. I was sent two bad Midland 6 meter antenna cables (made by Midland) and both was defective. That's when I ordered NMO mounts from The antenna farm. That way I could use the RG8X. 

Chance

WRJT366

   

 

I think this is the second complaint about a midland antenna I have seen in the past week. I heard that the "Factory tuning" may not be correct for all applications thus throwing off the SWR but don't quote me on that.

 

Your best bet would be to see if a local GMRS operator would have a NMO antenna for you to try giving you an idea of where exactly the high SWR is being caused. Try your antenna on the other set up, and the other setups antenna on yours and compare the results.

 

All of the vehicles I have set up use RG58 or RG8x with no problems at all, while others will say rg58 is no good, I really think theres only a problem for longer runs of the coax. This would leave solder connections which can be tricky. Excessive flux or weak solder connections can cause screwy SWR readings.

 

My call would be to check the antenna first, and the mount/connector second, those are my two suspect issues anyways.

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There are a variety of approaches that can be taken. My approach is generally a process of elimination, starting with as few variables as possible.

 

Do you have a another known good GMRS antenna? Does a friend have one. Do you have a know good connectorized cable?

Known good mount? Known good SWR meter that is rated for use at 467 MHz?

 

If you have a known good antenna and you know what its SWR is in its known good working condition, you could move that antenna over to your truck and check its SWR using your mount and cable. If the SWR is still good then your ghost antenna is the likely culprit. If SWR is still bad, then your cable, connectors or connections are where you need to focus. Don’t assume that outwardly nice looking solder joint means a quality connection at RF. A knick in the center conductor or shield can have a terrible affect on SWR as can coax dielectric damage cased by excess heat during soldering as can a hair of shield braid coming close to the center conductor.

 

I would consider another very simple test. Attach the Ghost Antenna to a mag mount, place the mag mount outdoors on a metal surface. This could be the roof of any car or truck (aluminum or steel s fine), or the bottom of a metal trash can turned upside down, or even a large cookie sheet or pie tin set atop a wooden post. I would try a short factory made coax or another one that is already known to be working perfectly.

 

What you try first has more do with what you have at your disposal to facilitate the test. Changing only one variable at time is always best.

 

 

Micheal

 

I have a 2017 F-150 aluminum body. Took the paint off the inside of the roof to make sure ground was good. Checked coax to make sure my solder work was good. Coax is 19.5' long.

I could get away with half of that. Coax is only 1 years old & never used before. I am useing the Midland 3 dB gain gost antenna. I was sent two bad Midland 6 meter antenna cables (made by Midland) and both was defective. That's when I ordered NMO mounts from The antenna farm. That way I could use the RG8X.

Chance

WRJT366

Edited for spelling.

 

Sent from my iPad using Tapatalk

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I don't have the technical expertise of the fine folks above, but I do want to extend a warm welcome to GMRS. I'm also an old CBer, but the willingness to help others and share information on GMRS is refreshing—as evidenced by the quick responses above. Once you get over this hurdle I suspect you will, too.   

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Yes I have two antenna's and only get a bad SWR in the truck. Also using a new MFJ cross needle watt/SWR meter. (Model MFJ-894)

Thinking the Midland antenna is tuned using the RG58 coax. For now I'm leaving the roof liner out of my truck until I get this problem resolved. 

 When I do find the problem. I will post about it here. In hopes that someone in the future will benefit from it.

 

Chance

WRJT366

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Ok I cut off the Midland PL-259 from the RG58. (I knew it was bad) Put a new PL-259 on it. SWR 1:1.8. I'm only using half the coax that came with it. Did not need 19 1/2 feet of coax.

Looks like Midland antenna's are tuned to 19 1/2 feet of coax. I hope I have better luck with the J-pole this weekend. Taking down the pld V58 CB antenna.

Thank you everyone for the input. 73's!

 

 Chance

WRJT366

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