RFB: "Then at that point yes it is the radius that counts as adding to the total length."
Well, you sound fairly well informed.
So, where in the rules is this stated since you decreed that we must not depend upon opinions? Forgive my "ear socket holes" but you are stating an opinion here.
I beg of you sir to enlist the advice of your close Field Inspector buddy as his would be a decision, not an opinion.
Here's A LINK to some enlightening reading regarding Top Hat antennas on the lowFer band.
Well MRAM, if my friend down there at the Denver field office was inclined to give his opinion, which is exactly what it would be limited to since he is not an attorney for the FCC, would you, sir, still be sitting there demanding a legal interpretation from him or would you gladly accept his opinion and his alone simply because he happens to be an FCC field engineer??? Would you throw away all of your opinions at that point...sir?
I never said lets not depend on opinions nor express them. There is a lot of that going around not only here, but in other forums as well..there apparently is not a problem with that is there? If so...what prevents you from expressing your concerns about it?
Someone else opened the door to how a top hat affects legal length measurements....I gladly stepped through it and held up my bright neon sign for all to see. But I never forced anyone to look at it or drive themselves blind over it.
To me, and yes in my opinion, the top hat issue is really mute since most seem to stay away from them regarding our world of Part 15. Care to give your opinion as to why the majority tend to veer away from actually installing a top hat? My two ear sockets are wide open to listen. 🙂
RFB
I have not tried a top hat because of the admitted prejudice in believing that it would not make a difference worth making. Well, and getting it to stay up there without tipping to one side and looking lop sided.
I do not have one installed on my setup because it is my opinion that there is too much controversy over the use of them for a 219 setup, suggesting that it is simply not worth the risk of being cited for that setup being outside of the length limit, as well as the little improvement it brings unless the top hat is of considerable size, which as you pointed out Carl, becomes a mounting and stability issue, in turn "tilting" the entire effort as a result.
Some things are simply meant to be kept simple. However I have found over the years that often the simple is too simple for the simple minded, and even can be too simple for the complex mind to grasp the simplicity enough to realize not everything requires complexity, nor is there such a thing as simple complexity.
RFB
As the signal travels up the a stick antenna, it suffers losses due to resistance, plus the end allows the vertical component of the pattern to escape straight up, which wont help. The hat acts as a capacitor, and in virtually all professional installations I've researched, it's always at the top, and so the overall signal retains more integrity and strength throughout its propagation pattern.
The 50' NDB tower at our airport manages a strong enough signal for the ADF in a plane to reliably point to it, about 35 mi. or so out, with just 25 watts, day or night. 284 kHz.
I keep forgetting to go over and take a pic of it.
Your comments, Ken Norris, have me back in the hat crowd with a question:
For a part 15 3-meter pole, what is a good shape or type of hat to attach at the top?
If there was a specification description or drawing of a recommended top hat that would be a good starting point.
And if trying different shapes and sizes of top hat, can the differences be significant enough to be measurable?
Try a flat hat first. 1 to 2 feet diameter. Re-tune. Run about and test. Then if so desired, try a cone shape, 5 to 10 degree angle, same diameters of 1 to 2 feet. Re-tune and test. Then later try a "squirrel cage" type hat of the same diameter, or a squirrel cage that also cones to the top, ie 2 feet diameter at its bottom, 1 foot diameter at the top. Mount the hat cage at the bottom of it to the top of the vertical. Re-tune and test. Then try it the other way around...re-tune and test.
RFB
The flat hat is being prepared right away. I think I'll do a hat a day. And this is making me wonder.... how does RF energy act in geometric space.
1. How does RF energy act in a flat circle?
2. How does RF energy act in a perfect sphere?
3. And all the conformations under discussion...
THAT RF energy acts different ways in differently shaped objects has been hinted at many times in these discussions. Examples include the suggestion that larger diameter pipes are better than thin wire, that a vertical antenna wider at the top is better....
Here is a link to a very well written and peer reviewed PDF about rf propagation in geometrically large environments.
http://www.cs.nyu.edu/web/Research/Theses/rajkumar_ajay.pdf
RFB
I just posted a reply in this thread but it didn't show up.
Here's a pseudo loop, i.e., a loop that isn't a loop.
http://www.antennex.com/hws/ws0201/nonmag.htm
I'm about to embark on some Spring projects, and this is among them ... except that mine will have a weatherproof TX box and tunable loading coil integrated into it. The idea is to create a balcony garden decoration that is in reality an AM broadcast system, for apartment dwellers or other situations where a stick antenna would be frowned upon by the manager or homeowner's association.
Ken Norris, the document on loop antenna experiments just got printed so I can spend the evening going over it with great interest. Really appreciate your sharing this novel information.
RFB, the white paper by Ajay Rajkumar reminds me that I meant to go back to school. Ooo-eee, it is one deep study. Just how smart are you, anyway?
Oh, Ken, yes I agree, there needs to be a whole department devoted to "stealth" antennas, disguised in the garden or looking like art objects or even appearing to be something else, like a combination bar-b-cue pit TV antenna. I read somewhere that some cell phone towers are built to look like flag poles or other "normal" objects.
I actually thought that maybe my next
outside antenna should be spray painted
green.
Also, I have been thinking of an indoor
installation that would be in the corner
of a room. It would have a big coil and
a stick that would go as high as the ceiling.
Grounding is a question.
Best Wishes,
Bruce, MICRO1690/1700
NANO90.9
QUANTUM13.560
Hi Bruce- I share an interest in indoor transmission antennas and right now my AM is using an antenna that serves indoor and outdoor quite well.
The SStran is on a small board, to raise it slightly off the floor, underneath a corner of a desk right below a front facing window. The antenna goes 2.5-feet up a wire and is fastened to the bottom of the aluminum window frame. The window frame provides 6-feet of vertical antenna which radiates on both sides, indoors and out. Out on the porch, at the top of the aluminum window frame is 1.5-feet of wire that stretches up the outside wall to the porch ceiling, where it stops. The signal if totally strong indoors and very remarkable outside for about 1.5 blocks in all directions. Because it is mounted on the same plane as the front wall of the building, the skin-effect carries the signal all the way behind the house where it is almost as strong as in front.
Grounding for that antenna is not connected, but I did try clamping it to the steel I-beam that runs the entire length under the floor, but that didn't seem to do anything. Grounding it to house electric ground at the water pipe brings too much hum. For an hour I had it connected to an unused telephone line, but it started going several miles and that was obviously a problem so it got disconnected.
Ken Norris's loop link is super interesting and the very first part of it, see Figure 1 about coax vertical, is something I haven't seen brought up here. And the loop examples really open a door on all kinds of possibility.
Bruce, the antenna in a corner was the first thing I ever had... I just ran the SStran white wire up a nearby corner with a glue stick and the indoor coverage was fine, not too great outside. But there was no ground.
We also need a good discussion about ground possibilities down in the basement, other than pipes.
RFB, the white paper by Ajay Rajkumar reminds me that I meant to go back to school. Ooo-eee, it is one deep study. Just how smart are you, anyway?
My professor once told me...while handing me my degree..."Now you are dumb enough to go learn something".
Regarding stealth antenna systems for Part 15 MW.....particularly those loops on that website link....let's keep in mind that most of those arrangements are a bit long for the 3 meter limit in making them operate effectively for MW. These displayed on the website are for 14Mhz. Some experimenting will be required with loading coils.
Let's also consider the uncertainty of just how any given inspecting FCC field agent will measure those in regards to either diameter, or radius. Either way, remember to compensate either of those two possibilities to sum up to 3 meters total.
RFB