I need help reducing SWR in my truck

[justme]

I purchased a Galaxy 77 export radio from Export Radios and mounted it on a “Michael Brolin” mount. I am trying to run a Wilson 1000 36” black fiberglass antenna on a Firestick Dodge channel hood mount. My problem is that I am running anywhere from 3. 5 to 8. 7 SWR and cannot get it below the magic 1. 5 number.

I have run 18 feet of coaxial cable through the firewall. I have checked the hood, left and right fenders, coaxial cable, “Firestick” mount, and everything is grounded.

I have tried Wilson 2000 antennas, Firestick antennas, and a K40 antenna to reduce the SWR below 1. 5 all of this to no avail. I have repositioned the Firestick mount 12 inches forward on the left fender and this did nothing. The only antenna I can get to work is a Wilson 1000 magnet mounted antenna on any body panel or a 102-inch whip antenna. Both of these antennas are unacceptable for my application.

I am getting ready to roll out to Pigeon Forge, TN for a joint SETDR/GLTDR in 24 hours. I need some help real fast to get up and running.




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Bronze 2001 Dodge Ram 2500 Quad Cab, Short Bed 4 x 4, ETH/DEE, leather, camper/trailer, keyless, 285/75R16 B. F. Goodrich AT's, etc, etc... Future BOMBer!!!!

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[Doc Tinker]

Justme - are you using a real SWR meter or the built in one? My built in meter shows real high, but an external one showed differently.

Doc

 

[justme]

I am using a real SWR meter.

By the way we have also checked the ring to ring, tip to tip, and tip to ring factors also.

It looks as though I will have to make the trip to Pigeon Forge and the SETDR/GLTDR gathering without any communications.

There are worse things that could happen!

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Bronze 2001 Dodge Ram 2500 Quad Cab, Short Bed 4 x 4, ETH/DEE, leather, camper/trailer, keyless, 285/75R16 B. F. Goodrich AT's, etc, etc... Future BOMBer!!!!

Life NRA Member

 

[Gary - K7GLD]

I'm not familiar with the terminology as to the radio or type mount you are using, but assume it's some sort of CB rig. I run HF and UHF Ham radio in my Dodge truck, using a set of Hamstick monoband antennas and a Kenwood TS-570DG rig for HF. The mounts are secured to each side of by tool/fuel box in the bed of the truck. I have found that there's a VAST difference between an ELECTRICAL ground, and a RF ground, and that there usually MUST be a large low impedance RF ground path/counterpoise available in order for a mobile antenna to load and radiate properly. Next is the need for GOOD QUALITY coax feedline - Radio Shack usually just WON'T cut it! - and then, the antenna itself must be resonant, or capable of being adjusted to resonance on the band or frequency it's intended for. Will your new antenna work properly on any of the other mounts? if it won't, maybe it is the problem. If it WILL work on another mount and/or feedline, then there's something wrong with the new setup that's not necessarily related to the antenna itself. You mention a variation in SWR, if SWR is lowest at the TOP end of the range of frequencies you want to work, the antenna/whip is too SHORT, and needs lengthening - if SWR is lowest at the BOTTOM edge, it's too LONG, and must be shortened.

Finally, to check the accuracy of your SWR bridge, reverse the input/output connections, forward becomes reflected, and see if readings are the same in this configuration - if NOT, it's an indication of bad sensing diodes inside the meter rather than an antenna problem.

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http://community. webshots.com/user/davison71 Early '91 250, 727 AT, 307 rear... Banks Stinger exhaust, intercooler... US Gear OD... Tweaked pump, upgraded radiator... MORE than a match for every new PS Ford encountered so far...

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[B.G. Smith]

Are you checking the swr on 1 and 40 as Gary states above and adjusting the ant. length as he suggests? Some of the Firesticks have a stub under the cap to adj, others you have to use the last wrap of wire to adj. You would be better off with a little longer stick with it in front of the cab, preferably top loaded as the Firestick is.

 

[Pine Sap]

I noticed that you did not indicate if you were adjusting the whip in and out of the mount via the little set-screw... you may be bottomed out or to far out?

Other than that it looks like you've done the correct things (and more)!

Did you get the Export tune-up?

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2001. 5, QC, 2500, 2wd, auto, 3. 54, 4 disc, long-bed, all the stuff, heated leather, patriot blue over silver, Brolin CB Bracket, stock4now!

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[RonaldLarson]

Good advise from KJ6Q. The fact that a roof or fender mounted antenna works well might point to the problem. Is your trucks hood grounded to the firewall using a length of braided shielding wire? If not, your hood is reflecting the RF back into the antenna,causing the SWR problem. It might be a floating Rf ground. Also, my experience with CB's is; tuning the length of the antenna is VERY difficult. Changes should be made in real small increments, like 1/64", and continuous switching from 1-40 is required.
Ever considered getting your amateur license? More fun, more power, and repeaters all over the country. I run 60 watts on my ADI 2 meter mobile, and it's a total blast.
Ron KC7MME


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[jolyman]

Hi justme. .
With a SWR between 3. 5 to 1 and 8 to 1 sounds like bad coax. 1) try your mag mount temporally in the same location on the fender 2)try a known good stick in mount 3)try new coax.

Its probably NOT the location (that might account for maybe an additional 1 or 2 units and the SWR would change when you moved the tip away from the truck and back . . But you would still get a DIP in SWR at the opperating frequency).

Try the meter at the antenna if you can (close. . 12"). If the SWR is low there then the problem is the long coax. (is the meter pigtail bad?????)

CHANGE and CHECK >>ONLY<< ONE THING AT A TIME.

AS stated before check GROUNDS -- make sure that the antena mount is making ground through the PAINT (use star washers between the mount and truck body)!!

Good Luck Jim W0AJL jolyman@hotmail.com

 

[PMalin]

If your going to make up another coax cable,
you may want to give RG-8X coax a try, and
PL-259 connectors with the extra bushing
to adapt RG-8X. Have someone familiar
with attaching the ends, solder them on.

Also, I was not certain you were "Tuning"
your antenna length. As with Firesticks
remove the cover at the tip, and adjust the bolt for the correct length to obtain best
swr in the middle of the band, ch 19 or 20.