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Has Anyone ever tried to mount the am transmitter and antenna on top of a tower with a remote wireless mic leading to the xmiter on ground level
I have a telescoping tower that will go to near 80 ft tall has anyone tried mounting power the transmitter and antenna all up the tower and
remoted the audio kinda a stl remote setup really ..
Joe leto
w0iw
Total posts : 45366Yes, there are reports of AM transmitters mounted on towers and other metallic structures but there is a problem that doing so may exceed the 3 meter limit on antenna, transmission line, and ground lead as stated in Part 15.219 of the rules.
There are those who will argue that the structure is a ground lead and those who will argue that it is not. Just be aware of the potential for trouble.
Regarding remote audio feed via RF, this is done by some of our forum members.
Neil
Total posts : 45366An FM transmitter at that height would be fine, assuming that you could verify that its field strength was 250u/m at 3 meters. You could feed it via RF, or, as I’ve done, via a wireless network Intranet stream.
Total posts : 45366Another idea would be mounted atop a tower battery/solar powered with such a small wattage coming from the xmiter it should be easy to solar power the whole setup and charge days and battery stores at night 🙂
Joe
Total posts : 45366“Has Anyone ever tried to mount the am transmitter and antenna on top of a tower … “
Yes, but in some cases when the FCC has inspected such installations, they have cited the operator for non-compliance with Part 15.
The issue here is that the top of a vertical tower or other above-ground conductor is not an r-f ground, even though the bottom of that tower/conductor _might_ be.
If the r-f ground terminal/chassis of an elevated Part 15 AM transmitter+antenna system is connected to the top of such a structure, then that structure will radiate — and likely be non-compliant with FCC §15.219(b).
Not the best news, for sure, but probably better to have this background information than not to have it.
Total posts : 45366Work around would be:This one is a freebie and it’s one that we found out doing some of our research. If you have a licensed electrician install an electrical outlet at the top of your structure then connect your transmitter to that you will be 100% compliant. The trick is to have your ground lead only a couple of inches long going to the electric box.
There has been many legal installs done this way and the FCC has not touched it because you do need a ground for safety reasons and electrical code requires a ground to be installed. This will save you a lot of headache with an elevated transmitter install. Keep in mind however if that silly petition passes that could change EVERYTHING on that one. So head to the FCC comment section and squash that one like a bug.
Total posts : 45366Sorry, but the “ground” receptacle of an a-c outlet with a “ground” conductor connected from it to a copper rod buried near the a-c service entrance does NOT provide a predictable/valid r-f ground — whether or not that outlet is elevated.
That conducting path will add radiating length to the antenna system of a “Part 15 AM” setup, which easily might be non-compliant with FCC §15.219(b).
Total posts : 45366It is my understanding, and I don’t foresee changing my mind, that part 15 transmission on the medium wave band using a 3-meter antenna performs best at ground level with a vertical antenna and buried ground radials.
I strongly disagree with anyone who imagines that elevating a stubby medium wave antenna has any advantage.
It’s been more than a decade now that this same subject goes round and round and it will never stop.
10 years from now we’ll still be hearing about elevated AM antennas and I’ll be repeating this message.
In fact, I’ll get a head start and repeat it right now:
It is my understanding that part 15 transmission on the medium wave band using a 3-meter antenna performs best at ground level with a vertical antenna and buried ground radials.
Total posts : 45366In the real world there are legitimate reasons for wanting to have an AM transmitter mounted high in a part 15 installation.
One such reason is SECURITY!
Transmitters mounted near the ground can be vanadalized and stolen so getting the whole thing up above easy access is a serious security matter.
Radioham hit upon one very excellent solution: “Another idea would be mounted atop a tower battery/solar powered with such a small wattage coming from the xmiter it should be easy to solar power the whole setup and charge days and battery stores at night :)”
Yes, the solar power combined with an STL (Studio-Transmitter-Link) to eliminate all wire connections other than the 3-meter antenna!
Now here is the ultimate secret to making an elevated install virtually equal to a ground-level installation…
ELEVATED RADIALS!
Almost no one talks about it.
Perhaps very few know about it.
But ELEVATED RADIALS will give an elevated installation the kind of punch enjoyed by a ground-mounted part 15 transmitter.
Total posts : 45366There’s another good reason to have your transmitter elevated. SNOW!
If I had a ground mounted installation, 5-6 months out of the year my transmitter would be under three feet of snow. Or more, depending on how the wind happens to drift it. My entire yeard gets covered with deep snow every winter up here. I’m pretty sure an antenna 1/3 buried in snow loses all effectiveness.
Hence my Procaster mounted on the wide of an attic window with no ground connected. Works for me.
I’m certain it’s not the most efficient. But in my situation it works perfectly. And I don’t have to try to shovel out the transmitter every few days.
TIB
Total posts : 45366Tim in Bovey woke me up: “There’s another good reason to have your transmitter elevated. SNOW!”
OH MY GOODNESS I never thought of that!
Even here in the mid-Mississippi Valley we could get a deep snow fall, what with the climate collapsing and all.
Thank goodness I know this while I’m still planning my outdoor tower.
As of right now my tower WILL be elevated.
Previously I figured I was somewhat safe on the security front because my yard is somewhat secluded, but SNOW.
Total posts : 45366Could put the ground mounted whip and transmitter under a tent like structure. A radome for ground mounts.
Total posts : 45366MRAM has another first class idea: “Could put the ground mounted whip and transmitter under a tent like structure. A radome for ground mounts.”
This kind of structure would also permit tuning and observing the transmitter protected from the weather.
Get a large enough tent to allow for a cot and a small desk and it would serve as a place where “daddy goes to avoid the family”.
Total posts : 45366Friend Carl suggested: “Get a large enough tent to allow for a cot and a small desk and it would serve as a place where “daddy goes to avoid the family”.
I said, “That’s what ham radio was created for.”
Total posts : 45366you know you know we’re actually really thinking on this one. When I was knocking down the petition for reasons that it should not pass this is a very good and valid reason why that petition should never pass.
an elevated an elevated transmitter in many areas will keep it secure as well. I couldn’t imagine living in say Detroit Michigan and having an AM transmitter on the ground. I bet your transmitter might last a total of 5 minutes if that before it gets vandalized by a bunch of criminals. The second thing was mentioned and that was snow. Even in the area I live in there are times where there is plenty of snow and with a large amount of snow on your antenna it could pose headache to your transmitter. Not to mention what that could do to the transmitter itself.
Elevated ground radials sounds like a AM version of an FM ground plane. I couldn’t imagine 30-foot ground radios in the air. I suppose one could put the antenna on the roof of a very large building with the permission of course from the owner could prove great results in range.
Keeping these things in mind when pondering on that petition and since we’re talking about ground and elevated transmitter these are all things to ponder upon.
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