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Elevation does make a

Home › Forums › temp › TH ATU Antenna Placement › Elevation does make a

February 24, 2013 at 2:27 am #30808
ArtisanRadio
Guest

Total posts : 45366

Elevation does make a (postive) difference, but if you elevate that ATU 8 feet or 15 feet or 22 feet above the roof and ground it to that metal roof, you may be deemed to be in violation of Part 15 rules – the antenna (whatever the length of your whip is) + feedline (no feedline with the Talking House ATU, per the FCC) + ground wire cannot exceed a length of 3 meters or roughly 10 feet.  At least, that’s the way the FCC has been evaluating long ground wires for the past while.

If that is an issue for you (it certainly would be for me), you can mount your ATU just above (i.e., inches) the centre line of your metal roof.  You should not need to run a ground wire, as there will be a capacitive coupling effect between the roof and the ATU.  That way, your ground wire will be of 0 length, and you shouldn’t run into any problems, should the FCC come calling.  If you do run a several inch in length ground wire to the roof, your installation may still be deemed to be exceeding the 3 meter rule, as the metal roof will probably radiate.

The safest installation, in terms of passing an FCC inspection, is to ground mount your ATU, and use radials (they will increase the efficiency of your antenna without radiating, much as mounting your ATU several inches above the metal roof).

But of course, the final decision is yours.

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