Well my iAM ATU arrived yesterday, and its all setup now.
Unfortunately my coverage is severely disappointing, barely reaching the end of the block. the meter reads about a 7 or 8 on the ATU.
Well my iAM ATU arrived yesterday, and its all setup now.
Unfortunately my coverage is severely disappointing, barely reaching the end of the block. the meter reads about a 7 or 8 on the ATU.
It seems all my signal is blasted into the overhead power lines, it travels via the power lines only, which causes an irregular and rather poor signal away from the lines, in fact its nearly non existent when your not near a power line.
While normally this could be OK, for an ATU and outdoor antenna the range should be much better, it barely gets out a 1/4 of a mile.
Its grounded with an 8 foot galvanized steel rod, Im thinking about tapping a ground over on the old pool pump pipes (the pump is long gone, all that's left is an old iron pipe from the 50s)
Is the proximity of the power lines to the antenna causing this problem? how can my range be fixed?
My ATU started out on the roof above the TV antenna.
I added some radials which seemed to help but not a great deal.
With all the hoopla over the ground mounted antenna video showing great coverage, I moved my ATU to a ground mount. I installed 12 - 20 foot radials. The ATU was mounted on a pipe about 3 feet off the ground. The coverage in a word - sucked.
I moved it to the side of my tower,about 25 feet up. No good, too close to the tower.
I put it back on the house above the TV antenna, 6 feet off the roof. This time no radials, no ground except to the ungrounded TV mast.
This time it works better than ever. Good coverage to 1/2 mile and has been heard (at least I knew what it was) more than 2 miles away.
Antenna placement seems to be a hit or miss thing so keep trying.
I am also very curious about the probable result one might expect from placing an AM transmission antenna underneath power lines.
The common reason for keeping antennas away from power lines is safety, but when your only ground space is under power lines it seems like it could be a problem.
I hope someone with more experience has the advice about how to integrate with nearby power lines.
It's an unfortunate real world circumstance, and not much can be done except to relocate the TX antenna away from the power lines, or move away entirely from being under the power lines.
The utility lines are absorbing the signal, particularly the near field (inductive), which is affecting the far field result.
Thus the power lines tend to "carry" the signal some distance and scatter it across all the other lines besides the one above your antenna. This is why the signal is spotty even near the lines.
It's one of those (a) vs (b) to cause (c) to point the finger at (a) when it was (b) all along pointing fingers at the other two.
If possible move the antenna system as far away from under the power lines as you can. Using old abandoned pipes that have been there for years make excellent ground conductors, use them! The more the better, meaning better ground contact for a return path.
In the instance where the TX was mounted up on the TV mast, ungrounded, just made that mast turn into a radiator, even more so since it was not actually grounded, that is why your range increased, the longer conductive element supporting the TX acted as the radiator instead of the one on top.
And I see no problem with that IMO.
But as others might say, that is exceeding the 3 meter length deal with antenna, coax and ground lead blah blah.
Technically it is, but all things considered, it's still less than 100mW radiating and those that got 2 miles plus range are not talking about crystal clear range that far either, but listenable so it's not like your flooding the channel or band with kilowatts. (rant over)
The Part 15 hobby world just has to put up with certain things until certain things get changed and that wont happen unless everyone gets involved more than just hanging a wire from the roof and calling it a day.
Keep experimenting with that antenna placement. The right combination will be found. As I always have said, every site, every installation be it 219 or 239 or 221, is going to have it's own unique set of difficulties (reality) to overcome.
Fight the good fight!
RFB
RFB offers good advice about experimenting. From my experience it is necessary at times to keep changing things until the desired result is obtained.
A 100 mW AM system is capable of sending a listenable signal (via car radio) out to about 1 mile and I have done this by erecting an outdoor antenna. It didn't work right at first but after tweaking and changing things it now performs as expected.
Don't give up.
Neil
Thank you folks for the help!
Well I tapped into that pipe, didn't really change much. So I'm going with one of RFB's suggestions and will relocate the antenna to the top of a relatively tall birdhouse located in the center of the back yard. Currently the antenna is in a dead tree directly underneath the powerlines.
I have 100 feet of coax, so moving this ATU around is pretty easy.