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Old 05-02-2016, 07:04 PM
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I know there is a million threads about this, but I'm really stumped here.

18' coax, confirmed no short
3' SWR jumper, confirmed no short
3' Firestik (have a 2' also)
Firestik quick disconnect
Uniden 520
DIY solid steel antenna mount
14g solid copper wire for antenna mount ground (about 40" long)

Multimeter reads "0" for ground test of antenna mount, and tested both coax cables and they are good. SWR is reading between 3.0 and 3.1 on all channels. What the hell am I missing here?

I thought that the antenna being so close to the 3rd brake light mounts (parallel) would have something to do with it, but I took the carrier off and re-tested with no improvement. Even swinging the tailgate out doesn't change my readings.

Any advice? Thanks!

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Build Thread - 2012 Cosmos JKU "BLUBICON"
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Old 05-02-2016, 07:51 PM   #2
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First make sure the nylon insulated shoulder washer on top of the mount is properly centered in its hole so it is preventing the antenna from shorting to ground. I that's good, odds are good the antenna mounting bracket isn't grounded well enough. A single ground wire like I see in the photo is not good enough for the RF ground antennas need. An RF ground is far more demanding than a standard ground provides.

Scrape the powdercoating away from the bottom of the mounting bracket so the bottom of the antenna mount the connector threads onto is touching bare metal. As shown below by my crudely drawn red arrows. Leave the powder coating in place inside the bracket's mounting hole and on top of the bracket.

Next make sure the antenna bracket is well grounded by grinding the powder coating & paint away as required so it receives a good ground.

You may end up having to install a braided grounding strap between the antenna mounting bracket and something well grounded like the tub or frame... again making sure the powder coating or paint is ground away so the ground strap is getting a bare metal connection.

The bottom line with a high SWR is that if the antenna isn't being shorted to ground via an improperly installed nylon insulated shoulder washer, there's likely an inadequate ground somewhere.

Or you're turning the tuning screw too far between SWR checks and you're missing the dip in the SWR at the tuned point. I go about a half-turn between each SWR test. And testing at ch 20 is all you need to check at, no need to also test at 1 and 40. If it's as low as possible at ch 20, it will be as low as possible at 1 and 40 too.
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Old 05-03-2016, 06:13 PM
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Old 05-03-2016, 07:03 PM   #4
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Either is fine but you can find braided ground strap on big rolls local to you there in Temecula. I've bought it at Fry's, Home Depot, Lowe's, Radio Shack, most auto parts stores, etc. over many years.

Also, I dunno what I'm doing this weekend since my wife has not yet informed me but if you can't figure the problem out, I'm available most weekends here in Escondido. I probably have 25' or more of unused braided ground strap in my garage.
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Old 05-04-2016, 12:36 AM
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Quote:
Originally Posted by Jerry Bransford View Post
Either is fine but you can find braided ground strap on big rolls local to you there in Temecula. I've bought it at Fry's, Home Depot, Lowe's, Radio Shack, most auto parts stores, etc. over many years.

Also, I dunno what I'm doing this weekend since my wife has not yet informed me but if you can't figure the problem out, I'm available most weekends here in Escondido. I probably have 25' or more of unused braided ground strap in my garage.

Ah you're kidding! I drove all over town today and couldn't find it anywhere. Went to ORW, 4WP, O'Reilly, and 2 specialty electronics stores. Drove right past radio shack because I was in a sour mood at that point Didn't think of Lowes or HD.

Thank you for the offer. I will certainly DM you if I get to my breaking point with this
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Old 05-25-2016, 06:31 PM
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Well a huge shout-out to @Jerry Bransford for helping me diagnose and fix the problem. I didn't drill the hole in the mounting bracket large enough and it was making contact with the bottom part of the stud mount, causing a short to ground. Drilled out the hole a bit bigger, added a little heatshrink insulation and presto! SWR down to 1.4

Looking forward to using it on the trails! Thanks Jerry!!
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Old 05-25-2016, 07:08 PM   #7
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You're entirely welcome David, it was great meeting you. Looking forward to meeting the rest of your family at the Big Bear meet & greet in July!

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