I've heard it said that an elevated ground plane does not radiate.
Why not?
What you hear and what is fact are two different things. What many people "think" is not true at all.
But you asked why don't radials radiate? They do.
Here's the answer from someone who knows...me....
Radials are put underground. That's why the don't violate rules. The earth is a barrier to radiation no matter where in the electromagnetic spectrum. That's why when they do nuclear tests they do it underground.
Radio waves like AM frequencies can't radiate from underground to above ground so they are allowed. What underground radials do is cause more signal to radiate from the antenna and contrary to beliefs of AM being a "ground" system the AM signal can't travel underground. The RF still travels from the antenna which is above ground. It's easy to see if an elevated ground or a long ground lead is radiating....anything that can measure RF will tell you. Audio cables radiate also. Unless they are well shielded with foil under the outer jacket.
What you hear and what is fact are two different things. What many people "think" is not true at all...
Yeah, everything you pointed out makes sense to me, but I've heard differently over and over again through the years. I've heard it here and every other part 15 related forum out there and elsewhere.
For example, how about Wikipedia?: https://en.m.wikipedia.org/wiki/Radial_(radio)#:~:text=The%20radials%20do%20not%20themselves,main%20part%20of%20the%20mast.
.....The radials do not themselves radiate, but may indirectly cause a small improvement in antenna radiation of short antennas by raising their point of maximum current upward along the main part of the mast...
So if radials do radiate, why hasnt someone cortected wili, and why has majority (even our late Richard Fry) always insist that they do not?
This is one of those topics that never has been clear to me. Consider carrier current and leaky cable, they usually run horizontal and they certainty radiate, so what the hell?
Elevated radials that are at a 90 degree angle to the radiating element, offset to each other by 180 degrees, and the offsetting radials being the same length, don't radiate. The waves cancel each other out.
Sloping radials, or radials in any other configuration, will radiate - they become part of the antenna. Sloping radials, in particular, are in common use in amateur radio installations.
I'd say more, but then I'd have to slap on a tariff.
I've heard it said that an elevated ground plane does not radiate.
Why not?
If you speak of radials orthogonal to the radiator, they do conduct current away from the feed point, hence absolutely radiate energy in the process. Put a field meter near and around the antenna and you will find stronger fields near the radials and less in between. Go further away from the antenna and these radial generated fields, due to the symmetrical nature of the radials, cancel each other leaving only the uncancelled primary radiator's fields to propagate. How many radials does one need for good cancellation? Read here to find out...
https://www.hamradio.me/antennas/radials-far-field-effects.html
@richpowers My main point is not whether radials radiate or not but they can't radiate from underground to space. I never said they don't radiate. But they cause an increase in RF from the antenna. That's why a stake in the ground can be 10ft or 100ft and you can have all the radials you want. The FCC doesn't care as what is underground doesn't radiate into space. All they care about is what is above ground.
But an elevated "ground", like a metal eavestrough around a roof, a metal fence, metal tower, it radiates.
But if the radials are just sitting on top on the ground and the grass grows over them to hide them and they do radiate then they are also radiating into space. They have to be in little trenches buried underground.
Equal length and opposite radials do not radiate in the traditional sense. They may increase the efficiency of the antenna (which is what they are there for) and hence you get increased field strength. But it is the radiating element that is doing that, not the radials themselves.
Some radial systems will radiate, as I mentioned. Sloped radials, only 1 radial (also known as a counterpoise), etc. But no, if you have perpendicular, equal length and opposing radials, they do not radiate. The current flowing in the radials cancels out.
I was going to include a reference to the Wikipedia article on radials, but it isn't the best. Doing a search on radials and radiate will give you the answer.
I'll throw in my article on radials...
https://www.hamradio.me/antennas/radials-far-field-effects.html