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Old 30-Sep-2012, 1:05 AM   #1
flim
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Defective antenna???

I just bought a Winegard HD7695P. Hooked it up temporarily and got no reception. Measured the two VHF terminals and they are shorted, zero ohms. Is this normal??? The two leads at the antenna with no leadin attached are shorted to each other and to the boom. Zero ohms in all locations. I'm an electronics tech and this does not seem right. Can someone confirm that they should not read zero ohms??

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Old 30-Sep-2012, 7:26 PM   #2
GroundUrMast
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DC resistance measurements tell you almost nothing about the RF characteristics of a component or system. In OTA TV systems, frequencies range from 50 to a bit over 700 MHz. A DC/ low-freq. AC VOM can't measure at those frequencies.

Many if not most baluns, matching transformers and matching networks will present low DC resistance on one or both ports.

Be sure the TV is set to scan for 'Air' or 'Antenna' signals, not cable.

Also, double check that none of the phasing lines are touching the boom.

Last edited by GroundUrMast; 1-Oct-2012 at 7:17 AM. Reason: emphisis of correct scan type
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Old 30-Sep-2012, 10:20 PM   #3
teleview
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Type , measure antenna impedance or measure balun impedance in the google search box.

Most Tv antenna baluns are a transformer design , wires wound on a ferite metal core.

With a DC meter it will read short circuit or open circuit depending on how it is connected.

Last edited by teleview; 1-Oct-2012 at 9:38 AM.
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Old 30-Sep-2012, 11:35 PM   #4
rabbit73
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Hello, Flim:

It would help us a lot if you would post your tvfool report so that we can see what the signals look like at your location.

As was stated above, a DC resistance measurement might be misleading. Just think of a full wave circumference UHF loop that is used in many indoor antennas. It would measure as a short, but it makes a good antenna for strong signals.

Likewise, in a yagi antenna, the center of a halfwave element can be connected directly to the metal boom because that point on the element is at an RF voltage minimum.

Please take a look at this Winegard video:
How To Troubleshoot a Winegard Antenna Cartridge Housing
http://www.youtube.com/watch?v=TlQke5QYbng

If you make the tests in the video and they are not conclusive, I suggest you try another antenna for comparison. That will tell you if the problem is the antenna or the signals.

Please let us know how it works out.
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Last edited by rabbit73; 1-Oct-2012 at 12:41 AM.
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