Mobile Installation with impossible high SWR

[AA3RA]

So, I have installed a Kenwood TM-271a into my Jeep. I ran new RG-8X cable to an Arizona Rocky dual antenna mount on the spare tire bracket. The antenna that I am trying to install is a Firestik 2M-4. I have confirmed that the cable is not shorted and the antenna center conductor is not shorted to ground. At 144Mhz the SWR is reading 3.0:1 and 3.7:1 at 147.995:(. I have ran a ground strap from the antenna mount to tub of the Jeep since the antenna is mounted on the tailgate. I have ran another cable from the mount to the rig. I have also swapped out antennas with the same results. I have gone as far as connecting the antenna system up to a Kenwood TM-261a with the same results. I would appreciate any input or suggestions that could be given as I have tried everything that I know.

P.S. The SWR meter was connected to another known good installation with a 1.3:1 reading so, I am ruling out the SWR meter as an issue.

[K9STH]

Check that the shield of the cable is connected to the chassis of the vehicle. Also, check that the shield is making a good connection at the radio end.

Glen, K9STH

[AA3RA]

Check that the shield of the cable is connected to the chassis of the vehicle. Also, check that the shield is making a good connection at the radio end.

Glen, K9STH

I have checked with a voltmeter that there is good continuity between the shield and the vehicle chassis. I have also confirmed continuity between the shield on the radio end to ground. I can only assume that the radio is getting its ground through the radio chassis itself as I can remove the ground lead of the power cable and the radio still stays powered on.

[K9STH]

Remove the connector completely from the radio making sure that it is isolated from ground. Then check the continuity to ground from the shell of the connector at the radio end.

The radio should be grounded through the mounting bracket.

Does the antenna work on a different mount? That is, have you tried the antenna on another installation?

How long is the ground lead from the mount to the vehicle chassis?

Glen, K9STH

[WB2WIK]

"Firestiks" are about the worst antennas in the world.

Why not use a real 2m antenna, like a Larsen NMO-150?

"Firestik" is a CB antenna company and I've tested many of them to confirm they're all pretty bad.

They actually sell a mag mount that has zero connection between the transmission line outer conductor and the mounting baseplate. I could hardly believe that, so I bought a second one, and it measure the same as the first one: Infinity. They were relying on the magnet itself to be a conductor, and it's not. Silliest design I've ever seen.

[AA3RA]

"Firestiks" are about the worst antennas in the world.

Why not use a real 2m antenna, like a Larsen NMO-150?

"Firestik" is a CB antenna company and I've tested many of them to confirm they're all pretty bad.

They actually sell a mag mount that has zero connection between the transmission line outer conductor and the mounting baseplate. I could hardly believe that, so I bought a second one, and it measure the same as the first one: Infinity. They were relying on the magnet itself to be a conductor, and it's not. Silliest design I've ever seen.

George, I did connect a Hustler SF-2 antenna to the same mount and feed line with the same results. I realize that Firestik is a CB manufacturer but, that was the only one that I could fine that was a fiberglass antenna. If I could get the Hustler to work I would use that but, it registered the same high SWRs.

[K0BG]

All vertical antennas require a decent ground plane under them. Mounting them in less than ideal places exacerbates the SWR issues, and a tire rack isn't an ideal place by any means.

As for the grounding... A DVM can check the DC continuity, but won't do much for the impedance. If you can borrow an MFJ-259B or similar, you can tell almost instantly what the issue is. How to fix the issue is moot at this point, because you don't know what is causing the high SWR.

Since you apparently need 440 as well, the Larsen NMO2/70BK is the best choice. As Steve sort of alluded too, when buying antennas, buying cheap is always a negative factor.

[W4DRH]

So, I have installed a Kenwood TM-271a into my Jeep. I ran new RG-8X cable to an Arizona Rocky dual antenna mount on the spare tire bracket. The antenna that I am trying to install is a Firestik 2M-4. I have confirmed that the cable is not shorted and the antenna center conductor is not shorted to ground. At 144Mhz the SWR is reading 3.0:1 and 3.7:1 at 147.995:(. I have ran a ground strap from the antenna mount to tub of the Jeep since the antenna is mounted on the tailgate. I have ran another cable from the mount to the rig. I have also swapped out antennas with the same results. I have gone as far as connecting the antenna system up to a Kenwood TM-261a with the same results. I would appreciate any input or suggestions that could be given as I have tried everything that I know.

P.S. The SWR meter was connected to another known good installation with a 1.3:1 reading so, I am ruling out the SWR meter as an issue.

AA3RA this is AK4OA, Columbia SC. When I read your post, I thought I had written it. I have the exact same problem. I have an Arizona Rocky Road dual antenna mount that is behind the spare tire. I bought two 4' firesticks thru Arizona Rocky Road, one for CB and one for my new 2 meter TM-271. I have an 05 Rubicon Unlimited with hardtop and rag top. My CB had high SWR until I realized I had the antenna cable upside down causing it to be grounded. Once I flipped it the right way with the insulator correct I had SWR about 1.2:1. On the side I was going to put my 4" firestick my SWR's were in the 1:4 or higher. I had a very smart ham c 50 years experiance look at it. I thought that some of the problem might be the tailgate door may be on some nylon bushingsand maybe a ground strap might help. I have not had time to try but there is grounding present. Finally after checking everything we could with SWR and MFJ antenna analyzer and finding nothing abnormal, he took off a Larsen 2 meter antenna and grounded it under the Firestick. This immeadialy dropped SWR to about 1:2.5 range which lead him to think it needed more counterpoise. There are several jeep websites that I have been meaning to visit to see if anyone else has had same problem c Arizona Rocky Road antenna mount. Please keep in touch if you come up with an answer. Thanks
Hugh AK4OA

[AA3RA]

AK4OA, it is really funny that you would post your reply yesterday as that is when when I finally got my installation complete and working with a decent SWR. A friend of mine (KA2ZEV) determined that the Arizona Rocky antenna mount was a total waste of time and money when it comes to being useful for 2 meters. The CB side on the other hand worked fine but, 11 meter is a totally different animal. The solution was to purchase two trunk mount (stainless steel "L" brackets) with a 3/4" hole for an NMO mount. I drilled three holes for each bracket right under the hardtop and inline with the outside each of each tail light. Now, I have my 11 meter antenna on the left hand side of the Jeep and my 2 meter on the right hand side. I did attach a ground braid from the mounting bolts (which I used 1/4-20 stainless hardware) to the inner body of the Jeep. I not sure that I needed it but, it never hurts. Either way my installation finally works and that is what it is all about. By the way, I purchased an Larsen NMO-150B 5/8 wave antenna for the 2 meter and on the 11 meter side I bought a 3/8-24 to NMO adapter for the Firestik. The NMO mount with the Firestik is actually a bit heavy for the mount and I will be purchasing a Larsen NMO-27c 11 meter antenna in the very near future. I hope this helps with your installation. I have an Arizona Rocky dual antenna mount for sale if you know of anyone that would like to buy one . :) 73 and email me if you need any other input. AA3RA.

[W4DRH]

When you get your install complete send me a picture79230

[AA3RA]

79632
When you get your install complete send me a picture79230

Here are the pictures of my install. The 2M antenna is on the right and the 11M is on the left. If you have any questions shoot me a PM.