No Ground Plane Dilema!! Fiberglass Roof LowBand 33Mhz

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chadg

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I read the forums but have never posted. But...

We took delivery of a new Kenworth eliptical tanker. The factory installed the antenna mounts & ran coax to the console. I put a PCTEL Maxrad MLB DC Series 30-35 DC Ground Antenna on the mount that I already had new in the package at the station. Today the local radio company came out mounted headset & radio etc. Radio is Motorola Maratrac. Tech. tried to tune antenna, no go. He called me and said the roof if fiberglass antenna and has no grounding. I even have a MONR-33 scanner all band antenna and he said the scanner hardly picks up highband channels let alone low bands. We use 33.72 Mhz.

Anyone have any options? I don't see any low band antenna without ground planes, I see 130mhz & 440 etc. no ground planes. Someone suggested putting foil or metal up under the headliner? Is putting metal strip on the roof & ground it an option?

Thanks in advance,
Chad Graybill
Bart Twp Fire Co. www.bart51.com
Lancaster Co. PA
 

pogbobo

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chadg said:
I put a PCTEL Maxrad MLB DC Series 30-35 DC Ground Antenna on the mount that I already had new in the package at the station.
If its a DC ground antenna you shouldn't need a ground plane :confused:

Check out Antenex model C30, it says its DC ground and base loaded for 30MHz and it does not require a ground plane ...

edit: somebody please correct me if I'm wrong ... I'm second guessing myself on this one
 
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pinetree

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You may be able to get a close match by running a wire from the base of the ant. where it comes through to each side of the cab. You can also run foil like that used on boats to either side. That foil is usually has a self stick surface. Without that you probably will not be able to get close to a useable SWR.
 
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Smith29180

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On our T300 KW we had the same problem and ended up using a mirror mount bracket .
Not sure what style mirror you have but it might be an option for you.
HTH
Ron
 

prcguy

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You can cut down many popular CB fiberglass mirror mount antennas for 33MHz. Home Depot sells a 2" wide aluminum tape that you can line the inside of the roof with if you stick with the Maxrad antenna. You want the most metallic surface area under the antenna and a single wire or two generally does not work very well. If you have already drilled a hole in the roof and installed the mount, take it out, run as many "radials" of foil tape as you can heading from the hole outwards to the edge of the cab and put the mount back so it pinches into the foil tape for a good connection. I've installed antennas on dozens of Corvettes using aluminum foil tape for the ground plane and its not a big deal. You might want to clean the fiberglass with alcohol or Windex in case there is some mold release compound or other slippery stuff that will prevent the tape from sticking.
prcguy
 

Don_Burke

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pogbobo said:
If its a DC ground antenna you shouldn't need a ground plane :confused:

Check out Antenex model C30, it says its DC ground and base loaded for 30MHz and it does not require a ground plane ...

edit: somebody please correct me if I'm wrong ... I'm second guessing myself on this one
DC ground and requiring a ground plane are two seperate issues.

A coaxial antenna needs no ground plane and is not DC grounded.

A j-pole needs no ground plane and is DC grounded.

A quarter wave vertical needs a ground plane and is not DC grounded.

A folded unipole needs a ground plane and is DC grounded.



Back to the task at hand, the foil tape radials sound like the best solution.
 

pogbobo

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thanks Don, I guess I was led astray at somepoint lol ... but thanks for clearing that up :)
 

Tommahawk

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Chad;

You wouldn't have to do this if Lancaster County got their act together!!! Remember that Opensky was the best thing out there and should have been online three years ago.

BTW are you still going the route of the vehicle crossband repeaters? Eden just installed cross-band repeaters in their vehicles last week. I do have their new frequencies. All of Manheim Township departments are upgrading to new repeaters over the next couple of months...


Take Care Chad

Joe
 
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