Agreed that the radiation from the globe will not be significant but my point is that it is not zero.
Since the RF current in a loading coil has a vector component of the current along the axis of the coil which is due to the pitch of the winding then these also will radiate, but this will also most likely be insignificant even though not zero.
I posted in response to the statement: "It has been proven, by demonstration and by the numbers, that cap hats and globes and loading coils DO NOT RADIATE."
Neil
It might not be absolute zero...but the amount present on the globe will be insignificant that the only way to get any nth decimal point measurement while preventing any influence from the mean radiator, would have to be purely by number crunching. THAT is MY point..as well as my point about the nit picking.
In any case, both of our positions are correct no matter how it's sliced and diced. Not enough there to make ANY difference, hence so little there it can be ignored as if it were zero..and should be ignored as it has no relevant additional radiation being emitted versus the overall radiation pattern being emitted off the main radiator.
That is unless the desire here is to nth decimal it to death just to attempt to make it significant. Still the real world result will simply make that miniscule number a variable to the likes of the noise floor.
IMO..it's a waste of time and effort to beat the dead horse further to death here.
Nit picking never accomplished anything. It certainly isn't here either.
RFB
Respectfully, RFB, presenting accurate information is what we all try to do (or should). When a statement is made which contains inaccuracy why not point out the inaccuracy even though it may have no immediate practical consequence to the discussion at hand?
Is it better to leave readers with the impression that a sphere or a loading coil does not radiate or to explain that they do radiate but the radiation is not of practical consequence? Which is more accurate?
You may label what I posted as you wish but my intent was to present physically correct information. What the readers do with this information is up to them.
Neil
If the intent is to present accurate information, then let's focus on the item..not quotes from posts to justify or point out..ok?
The fact is...any radiation off that globe will be insignificant...and THAT IS accurate information. You yourself admitted to that. Yes there is a TINY bit of radiation from that globe..but not to a point where we all must stop everything and focus on that miniscule fraction which won't make or break the prospect of this antenna design and it's main intent..to maximize the efficiency of the short radiator..to which that radiator IS the 3 meter stick..not the globe, not the cap hat, not the loading coil or anything else.
This is a hobby forum, not a science university theorem forum. Not to offend, but the majority of members here are not working on the level of Einstein, nor should this forum put off that assertion either.
Now I dont claim to be the know it all..but I did learn about the difference between relevant data versus irrelevant data, and I also learned that the irrelevant data tends to clog up the works more than it helps. It also prevents progress.
I'm not saying your info is useless..in fact it's quite useful. However neither is my info and prospective. The readers can use it either way they see fit..spend hours on the miniscule..or proceed with progress.
The horseless carriage did not stop from becoming reality simply because someone pointed out that it doesn't require the routine of feeding and cleaning up what comes out of the tail pipe.
RFB
In every discussion about cap-caps, or capacitor caps, what I find lacking is a true and consistent definition of what a capacitor-cap is shaped like, in physical terms.
One time it's a bunch of prods fanning out horizontally, like upside-down ground planes, another time it's a flat pie-tin, and now it's a sphere.
No one has pinned down a true shape that identifies a component as a cap-cap.
What I take from the most recent discussion is that different shapes have different RF performance characteristics. So the shape must be a significant facet of cap-capping.
Furthermore, if we put that big sphere up in the air, a red-tailed hawk is going to sit on it watching for rabbits. Have you taken into account the capacitance of a red-tailed hawk?
Carl, I will try to add a bit by addressing your concern about what is a true shape, etc. If we define the top hat or cap by function rather than embodiment it may be easier to approach the subject.
First, the function of the top hat is to increase the capacitance the antenna system "sees to the Universe" which reduces the capacitive reactance of the radiator system. This means a lower inductance coil can be used.
Second, the function is to increase the current along the vertical radiating element and thereby increase the RF radiated. The top hat does so by providing a path for the current to follow at the top of the monopole. Otherwise, the current at the top would be zero.
Third, if we require that the top hat does not radiate for legal or other purposes then it has to be physically symmetrical around the axis of the monopole and itself have zero height. Doing this allows the RF fields created by the currents in the top hat to cancel since any current path will have an equal and opposite path on the other side of the monopole connection. This can be done with two or more wires, a pie plate, a 4 leaf clover shape, frisbee, or any conductor as long as the symmetry is maintained. Note that this applies only if the dimension of the top hat is small compared to a wavelength.
Hope this helps a bit.
Neil
Radio8z has nailed the definition of a cap-cap for purposes of part 15 AM operation, as far as I'm concerned.
He has given the function of the cap-cap, and its necessary physical form.
I am now satisfied that I understand what a cap-cap is meant to do, and what sort of physical shape it needs to conform.
Based on that, the sphere is not a cap-cap, since it has vertical dimension. The sphere shown above adds 18" to the vertical length, but looks Tesla-like and therefore interesting.
AFTER-THOUGHT: UNLESS the sphere is BOTH. It may both add 18" to the vertical length AND function as a cap-cap owing to its horizontal width.
The sphere may be a brilliant achievement in part 15 technology.
the sphere height of 12" is considered in the overall radiator height. from base of radiator to top tip of sphere is 3 meters.
The shape of a vertical antenna.
Now things are getting interesting.
A 4"-diameter vertical topped with a 12"-sphere, total height 3-meters, when viewed as a total object, is an antenna with an unusual shape.
Maybe there are "ultimate" shapes which would be the most maximum ideal of all.
Consider the common bell, in the acoustic realm, with its outward flare toward the bottom. I once read that an experimenter made a bell that flared inward at the bottom and the result was a tone in the major-key, based on its overtones.
It should be said that a common bell shape produces a tone in the minor, overtone-wise. That is why bells tolling can seem mournful.
The sphere may be a brilliant achievement in part 15 technology.
it's an old concept just recently adopted by tis antenna manufacturers but hams have used them on short verticals for 160-75 meters (mostly for mobiles) for years. ever see a "texas bug catcher" or an "egg beater"
Then, what about a ten-foot high sphere?
Tell the neighbor-noses that it's art!
It would be art. Anything to do with radio is art to a part 15er.
Plain old towers make sight-seeing worth-while.
kc8gpd, you have set me off on the trail of adding to your interesting idea by making adjustments and alterations.
Imagine a large 3-meter high sphere mounted right above the ground.
Where should the RF be applied? Down on the ground side? I don't think so.
I think a shielded coax should deliver the RF to the very center of the sphere, where it would flow in all direction in a uniform and symmetrical pattern.
The coax would be within the 3-foot space and therefore its 1.5-meter length would not count as a "lead in."
Unless such a design would cause a perfect signal cancellation, which would be the exact opposite of the desired goal.
if such a large sphere worked well on low band i would think that tis stations and hams would have adopted them long ago. at vhf and up hams use spheres that are large compared to wavelength but no one else.
I'm thinking this design used with a well designed 50 ohm class e TX using a DDS synthesizer with a GPS reference would really kick some butt. all functions could be setup for remote control from tuning to tx power adjustments and monitoring to allow for accurate tuning without getting capacitive coupling between tx and body or DMM probes.
The TIS here (WQH744) has their TX and ATU in a small metal shed which helps keep stray inductance from affecting the tuning of the antenna. Their main issue is keeping the system peaked. There are days when it comes in like wildfire and other days when you can barely detect a signal.
Their system is a Radio Systems TIS package and antenna.
RFB