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Author Topic: How to test auto glass for glass mount?  (Read 2854 times)
KL0PE
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Posts: 24




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« on: December 26, 2000, 12:23:11 PM »

I've read that cellular phone shops can check auto glass with an ohm meter to see if it is suitable for a glass mounted antenna.  I was wondering if home equipment could be pressed into service for such a test.  For example, is it possible to use a common digital multimeter, with some modifications perhaps, to check the resistance through auto glass?
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N2HBX
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Posts: 162




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« Reply #1 on: January 01, 2001, 01:24:19 PM »

When I was doing a lot of cellular work, we used a test cable that consisted  of the inside coupling box and a cable to connect to a capacitance meter.

We set the meter to a reference value with the cable and box connected but not touching the glass.  Then we would place the coupling box on the window.  If the value changed 2pF or less, it was considered suitable.

Bear in mind, these tests were for suitabilty at cellular frequencies.  For VHF or UHF, as long as you don't have one of those speciallized silver tinted or heated windows, you should be OK.  If you have them tinted with that aftermarket film, you may need to cut the film that is under the coupling box to get a proper match, since many of the aftermarket tint films are metallized.  Check with your owner's manual or dealer to see if your vehicle has that speciallized glass.  Also, avoid placing the antenna directly over the defroster wires on the rear window.  If you can get it between the defroster grids, that's OK.  Just don't have them running directly under the antenna.

73, Larry, N2HBX
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K2RTG
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Posts: 1




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« Reply #2 on: January 09, 2001, 04:50:22 PM »

This may sound a little bit off the wall.
 When I installed my Larsen dual band glass mount on my Blaser I did the following.
To test the tint to see if it had a metal film, I used a VCR and the remote. I had the VCR outside my car
and from the inside I put the remote where the tint was and tried to operate the VCR. I turned it ON/OFF and changed the channels. Can you picture this? I was told that the IR from the remote would not pass thru the metal film and It would go thru the dark tint.I suppose any device with IR remote could be used.
Like I said it sounds a bit strange but I had all the test equipment at hand.
Dave Kopp K2RTG

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AA9HD
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Posts: 10




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« Reply #3 on: January 10, 2001, 03:01:16 PM »

what i did was use packing tape to tape the couplers to the inside and outside of the glass.  then i keyed up my club repeater, about 20 mi. away, with my ht running through the antenna and asked for a signal report.  i received a favorable report and went ahead and installed it.  no problems until the assembly outside became a disassembly while on the highway Wink
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WB5MPV
Member

Posts: 1




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« Reply #4 on: January 19, 2001, 09:48:22 AM »

I used a "stud finder". On the windshield of my Chevy Lumina minivan it would not calibrate. On all other windows it worked well.

My 2m rig had very high SWR with the antenna on the windshield. The stud finder helped me locate a spot that would be acceptable which turned out to be the window class on the side by the windshield.

Since then I have used the stud finder several times and it worked well in assisting me in the evaluation of suitability for thru-glass antenna mounts.
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