With your Monster Station an fcc inspector would become very befuddled when he only found the dinky 100mW and a common 3-meter pole.
He would surely think something was going on, but he wouldn't be able to find a clue.
Ken Norris:
Have you tried anything yet with cage monopole?
Very interested to hear your results.
Not yet ... holiday weekend you know ... painting front of studio, driving taxis, trying to keep up with announcements and reports on the air.
Gotta go ... seeya later ...
So, if I build a cage monopole, and integrate the loading coil, should it go at the top, the middle, or the bottom?
What are the compromises to look for in each case?
Ken, my cage-monopole right now is on FM, where no loading coil is needed.
My AM experiments with cage monopole are entirely imaginary, but are definitely on the agenda.
Now, just all at once, I wonder if there are shortwave apps for the cage. Hmmm.
I do believe in the cage, as you can tell, by my observation that on FM it does better than a single wire. But the improvement is in signal stability within range, not too much increase in range.
Most of the antennas used on Part 15 AM are base loaded with a very few using center loading. I'd start with base loading as that is the most common approach, just my opinion.
I know base-loading is the most common, but the question remains as to what the differences are and how they affect the signal.
One of the reasons for asking is that If I can get enough band width with the right coil wound on my 12" pipe, say for 1500-1700kHz, then maybe the increased bandwidth characteristics of a cage monopole will allow me to tune to frequency with only a large vernier air cap with little penalty, rather than having to deal with coil taps on so large a diameter.
Another way might be to make the pipe a foot or so shorter than 10' and tune with a small telescopic stinger.
Also, I could make the pipe in two sections with a fitting and wire clip connectors, such that I could put it in the back of my Blazer and transport it, along with a rolled up ground grid, and not have to spend much time tuning to resonance.
Somewhere on our site there are some esoteric writings on the theoretical differences between center and base loading but to me, MRAM's center loaded antenna definitely demonstrates that it works.
The portability factor for the center loading looks like a great reason to give it a try!
A new idea hatched during experiments with a dipole antenna made from lamp cord. What if four dipoles were strung in a cage monopole arrangement?
Obviously this doesn't apply to AM medium wave Part 15 operation, but to shortwave transmission at 13.560mHz in projects with Talking Pixie2 and the new Big Talker 3-transistor projects.
The text books say a lamp cord di-pole has a typical impedance of 72-ohms, therefore stacking four of these in series would bring the impedance down to 18-ohms.
What are the expected advantages of a horizontal cage monopole? That's what I wonder.
Say Cal ... I'm a bit confused here. You are talking about a cage monopole, then a cage dipole, then a cage monopole again. So which thing is your question about.
FYI, I've kind of put my my efforts with cage monopole on backburner for awhile, because I feel it isn't the most imminent project for now. Why? well ...
AFAICS the main advantage of a cage monopole is bandwidth. A cage dipole should have even more for bandwidth. Therefore, I think it's a better experiment to try with FM BCB, or short wave Tuning an AM BCB system to peak resonance appears to still be the best way, i.e., I think gaining bandwidth for easier tuning is an OK goal, but I doubt it will improve range or signal quality over a matched loading coil/stick antenna system, so I'd like to see how to best improve that.
I really like the idea of tuning the coil via the stylus method. More on that later ...
I agree that confusion set into the ongoing discussion about cage monopole, complete with a mistake I made in one of my posts.
At the outset of the discussion, Mr. Ken Norris was looking for an advantage to a 10-foot AM antenna by way of better range. Then at the more recent posting Mr. Norris expressed doubt that cage-monopole would be of benefit in an AM medium wave Part 15 installation..... Well, to the best of my understanding a cage-monopole is a substitute for a wide-width pipe antenna, known to increase the bandwidth at the operating frequency. This would not increase range, but would increase frequency spectrum for the audio modulation.
My variation on the cage-monopole discussion was to contemplate a horizontal cage constructed of four dipoles connected in parallel. My mistake was to accidentally say "connected in serial conformation," which I don't think makes any sense.
As indicated, I run an FM cage-monopole and the increase in range is just barely observable on the S meter of a receiver at the other end of the house.... very small. BUT the big advantage I've found is that the signal is solid everywhere in its range and is not fluttered or multi-pathed by me walking through the house. Is there a comparable problem on the AM band? Not that I've noticed.
Hope you try it sometime.
My last good working installation was with
16 ground radials and the SS Tran sitting on
the ground in a water tight enclosure.
I had good results with one (less than 3 meter)
copper pole. But there was a gigantic top hat
sitting on top of the pole. It had four spokes,
and each one was a little less than 2.5 feet long.
I had a two mile range on the car radio in some
places - with a listenable signal. It was weak
but completely readable. But my coverage area
was not a circle. It was a complicated area with
nulls and peaks all over the place. As you guys
know, life has gotten in the way and this set-up
has been off for quite a while.
But - here's my point. First of all my tuning coil
was big physically, and it was wired directly into
the inside of the SS-Stran, where the small internal
inductors are. The small internal inductors were
all out of line, but the big coil was wired in their
place. i had no idea how to make this coil. So I
just wound a lot of turns on a PVC pipe. (Fifty?
One hundred? I don't remember.)
OK. Heres the really crazy part. Each coil turn had
a tap. (It took a long time to make it that way.)
I tried all the taps to try to get a peak. When i did
this I was very disappointed because I only achieved
a small peak on one tap. i decided that the experiment
was a failure, and I went into the house with my son,
and we watched a whole bunch of "Sponge Bob" episodes.
We watched Sponge Bob, Patrick, Mr. Crab, Squidward,
Mrs. Puff, and all of those other crazy cartoon characters
do the really stupid stuff that they do. Then I felt better, and
decided to try again.
After thinking about the problem, I literally tore a ferrite rod
(I guess it's not really ferrite) out of an old radio.
Then I went back outside and turned the set-up back on.
I tapped the coil tap that gave me that little small peak, and
yup - there it was - that frustrating little small peak.
Then I shoved the "ferrite" rod into the tube, and blammo!
Big peak in signal!!! Wow!!!
OK! So actually this is really my point. I didn't design this
coil. I just basically kept trying stuff till it worked.
So if I ever get this thing on again, I will try four copper poles
coming up from a central point. They will fan out. How far?
I don't know. Connect them on top? i don't know.
I just keep trying things till they work.
By the way, I think that the AM cage antenna and the
FM cage antenna are really two very different animals.
On FM, the antenna is operating near the wavelength
of the operating frequency. On AM, the cage antenna
as we have described it will just be a big lossy capacitor
again. Hopefully we will get good radiation resistance,
and the thing will work.
Best Wishes,
Bruce, MICRO1690/1700
"On AM, the cage antenna
as we have described it will just be a big lossy capacitor
again."
Well, not if you build a decent coil for it, just as you would for a stick. The cage principle is simply an inexpensive way to 'cheat' making a large diameter antenna with more surface area, which should help increase the efficiency of the loading coil (ref Phil B).
Since a benefit is also more bandwidth, then theoretically, it should be easier to tune to peak resonance, In that case, the coil taps would show more slope at peak, i.e., more like the center of a curve than a spike, and less critical The drop would occur gently at first, then run down exponentially.
If you were to combine the setup with Brian's (see Carl's latest Low Power Hour segment) stylus coil tuner and a very limited-range air cap. it might solve the tuning problems associated with stick antennas.
I think at some point it will be worth the time and effort to experiment with it on AM radio, and most decidedly more fun to play with, but right now I just don't have time, so trying some other ideas to increase the efficiency of more traditional systems is better for me.
.... But who know? If I find the 'right stuff' in the way of time and materials, I might just go for it anyway! 😉