What is the heightest you can have a antenna on Part15 AM??
There is no height limit per se for part 15 AM, it's the legth of the ground involved with the height which creates the problem.
Per the letter of the law the transmitter would have to sit on the ground to keep the antenna and ground lead within 3 meters.. however, it has been common practice for almost 40 years that all part15 installs have been 10 to 20 feet in the air in state parks, and none have ever been forced to comply with the 3 meter rule or discontinue operation. So take away from that what you will..
Rich Powers Part15, Take 2..
There are safety factors that dictate the height of antennas.
Some municipalities have height limits for poles, towers and antennas.
Also the F.A.A. requires antennas higher than 200-feet to be registered and lighted to warn aircraft.
Anything mounted in the air must be very securely attached so it doesn't blow down in a storm and injure people below.
I have been tossing around the idea of attaching a 400 foot antenna wire to my drone, running it up to 400 feet and see what happens. Of course my drone has only 22 minutes of battery power so this would be a short range project!
Jim Henry HBR Radio 1610, serving Honey Brook, PA. and NW Chester County.
Jim Henry is thinking: "I have been tossing around the idea of attaching a 400 foot antenna wire to my drone."
400-feet of wire would be heavy, can your drone manage the weight?
Make it easier. There is no reason for so much length... the 1/4-wave at 1610 kHz is more on the order of 100-feet.
Getting the antenna up and stabelized while you tune the transmitter might give you a few seconds to judge the result...
Could you drive off to do listening tests with your drone in the air?
Use a balloon.
Druid Hills Radio AM-1710- Dade City, FL. Unlicensed operation authorized by the Part 15 Department of the FCC and our Resident Hobby Agent.
Helium balloon is the best idea.
Nobody has answered the question??
Answered it in post #2
Richard Powers answered in Post # 2.
And then I added more information about the height limits in my Post # 3.
I trust that you are not confusing height with length.
An AM antenna under Part 15.219 may be 3-meters in length.
The rule does not say how high the length of antenna is placed, but the limitations we have mentioned are the practical and common sense limits.
What if you use a no ground plane antenna like a vertical antenna??
DJbout it asks: "What if you use a no ground plane antenna like a vertical antenna??"
Wouldn't matter. The same height conditions that Rich Powers and I have described would apply no matter how you do it.
When you talk about "height" you are automatically talking about an antenna's height above the earth whether it's horizontal or vertical.
Balloon is a much better idea.
Jim Henry's balloon idea for raising an antenna up in the air seems good in a fantasy imagination because it raises straight up and holds the antenna steady.
But you know how it is with the real world. Things don't always go the way you expect them to.
After thinking about it I now realize that the wind would make the balloon go east pulling the antenna which would yank the transmitter up into the air until the only thing holding it back would be outstreatched power and audio cables.
The wind would grow stronger and pull the cables free and the last time you would ever see your transmitter it would be rising into the night sky.
The next day there would be a story in the newspaper about an antenna dangling from a balloon wrapped around power lines causing a massive explosion and shutting down power to Atlanta.
Could be, but then it was only an intellectual exercise...
I have been wondering about this thread...
Your question was very brief and didn't tell us what you are thinking about doing.
Are you thinking about putting an antenna up high?
Let's ask this: what is the highest place you have available to put an antenna?
Doesn't do us much good to talk about putting it higher than you can possibly do.
It is easier for me to solve a problem if I know what problem we are trying to solve.
It was my idea, not Jim's!
DHR corrects the historic record: "It was my idea, not Jim's!"
I can truthfully testify that Druid Hills Radio was the first to suggest using a baloon.
What I saw happen next was Jim Henry agreed about using a baloon.
I sincerely don't think Jim was trying to take credit for originating the idea of the baloon, and when I suggested refinements and cautions about Jim's baloon concept, it would have been well to add a footnote crediting DHR with being the first with the baloon.
The best we can do is guard against such mis-credits in future threads.
Perhaps a metalized balloon, 3 meters in diameter connected as an antenna.
It takes the transmitter up and uses a wireless STL for audio feed. The whole shebang runs on solar assisted battery power.
No ground, no height limit.
by MRAM 1500
Charter Member - Association of Low Power Broadcasters
Chairman - ALPB
MRAM explains how to get up:
"Perhaps a metalized balloon, 3 meters in diameter connected as an antenna.
"It takes the transmitter up and uses a wireless STL for audio feed. The whole shebang runs on solar assisted battery power.
"No ground, no height limit."
Carl thinks for a long time and then asks... how high would it go and would it blow into another state?
I am feeling better now.
Yes it was DHR's idea, but I think either Google or Facebook has floated a trial ballon (pun intended) about putting wireless access points on balloons.
Actually this idea was "floated" during one ARRL Field Day a few years back. A helium filled balloon with a single wire about 100 feet long.
If using a moored balloon there are rules to follow. The big one a deflation device that will trigger if the balloon becomes untethered. How high the balloon can go is related to how close the balloon is to an airport. https://www.ecfr.gov/cgi-bin/text-idx?c=ecfr&rgn=div5&view=text&node=14:...
Balloons aside, the question of how high your transmitter is, as already pointed out, is really a question of how long the ground. Even if you do not attach a ground lead, it will still be grounded (unless your running it on battery power..
I've mentioned this before, but as a 1981 TIS survey concluded (systems much like our own):
"If the system makes use of commercial AC power, as nearly all do, the power ground will unavoidably become part of the antenna ground system. This may account for the fact that some antenna installations have been found to radiate tolerably well with what would otherwise appear to be a rather inefficient grounding."
Thats from page 56 of https://archive.org/stream/highwayadvisoryr00turn#page/56/ - By the way the whole book (it's downloadable) is very interesting and contains a lot of information which can equally apply to our part 15 installs since TIS stations are very simular.
No, the rules make no specific mention of groud being aquired by power or audio leads, but common sense does. If you have a transmitter 30-40 feet in the air with no "ground lead" attached, then your still going to have a 30-40 foot antenna system, it's just taking a different route.
The thing I find most frustratiing about 15.219 is that not even the certified transmitters, with particuar focus on the long established and most frequenty used transmitter used for the last 40 years -the Talking House, which was certified despite the fact that it never has ever actually conform to the 3 meter rule.. Rangemasters and Procasters do, but only if you install them at ground level and run via battery power.. And, as previously mentioned 40 years of common use of part 15 in state and federal parks, none of which even come cose to conforming to the 3 meters.
This has been eating the crap out of me lately.. If you wan't security that your install is 100% legal, well, that's almost impossible. The actual rules are apparently secondary, no one anywhere has ever complied to the letter.. It all based most entirely on if the inspecting agent decides he will allow it.
The most prudent you can be is to keep your range in check for a reasonabe unlicensed install.. if you are achieving over a mile radius then your getting into licenced low power ranges which obviously isn't kosher.
Of course this is all just my own deduced opinion based on research. I find the farce of 15.219 very disapointing, either rewrite it to conform with what has been clearly deemed acceptable to the FCC for the last 40 years, or enforce it as well as not certify transmitters which don't conform. Of course it's doubtful either will happen. My objective has been to insure legal operation, but the deeper I dig the more obvious it becomes that the FCC has decided that some are allowed to break the rules, but others have to obey it.
So how high can you have your transmitter mounted? To be honest that depends on where it's at and who you are and weather you're playing music or not.
What a disappointing mess.
About a year or two ago we had one come loose in Maryland and it came up here to South Central PA. It was an un-manned military observation blimp. I guess it didn't have one of those devices and it was dragging its steel tether which was a couple thousand feet long with it, doing considerable damage and ripping out highway guard rails along the way. It's a miracle that no one was killed.
For my part I very much appreciate the exploration you have done into all these compliance questions and your conclusions are very well reasoned and fit the picture of what has taken place in the part 15 experience over the years.
The only view I have of what's true and real regarding part 15 matches exactly what you have said.
Although I am sure it's in the background of your thoughts, I will also mention the factor of luck, which comes down to whether someone complains about you to the FCC.
If the FCC comes to inspect based on a complaint they might be more inclined to find a reason for shutting the station down to neutralize the complaint.
The issue of complaints is a whole dimension in itself. Some complaints are legitimate, such as an interfering station causing trouble to a licensed frequency.
Other complaints might be petty and jealous such as against a station that is causing no harm to licensed neighbors.
The best advice is don't pee in the public swimming pool.