Antenna...E Field

[pwdrive]

Referring to the attached pic:

It's a representation of a Beverage antenna (aka wave antenna) I can't quite make out what is supposed to be in the white inset, I understand the wave tilt but it's the three arrows that are shown, two of them are shown as Ex and one is unnamed, can anyone confirm what the three arrows represent? Also posted on UKVRR:

   

Full article here:

https://archive.org/stream/TheBevera...ge/n0/mode/2up

Lawrence.

[Murphyv310]

Hi.
I'm no expert on Beverage aerials, the chap I know is though (its Bobs son form Sorn) he isn't on forums sadly and has always said he has no intention.
I could ask him to give me a written blurb on the theory of the aerial but I only go there every couple of months or so.

[pwdrive]

I can (more or less) understand what's happening in text form, it's getting a picture into my head that I find difficult, all the texts say that when the EM wave travels over an imperfect earth then tilting of the wave will occur due to the different velocity factors involved, I understand that bit....texts then go on to say that because of that effect a horizontal component of the E field is produced due to the elliptical polarization that results from the wave tilt, I can more or less understand that too....texts then go on to say that it is that horizontal component that causes the signal current to flow in the wire, the Beverage antenna animation on Wiki shows that and I've assumed from that animation that the now horizontal part of the E field is on the same axis of the wire?

If that is so then how does the inset diagram (with the three arrows) in the picture fit in relation to that or isn't it supposed to?

Anyone?

Lawrence.

[Murphyv310]

I'd like to know too.

[pwdrive]

Beverage, Rice and Kellog's notes from 1923:

http://ra6lbs.ru/Papers/Bv%201923.pdf

Lawrence.

[reset]

It appears they are comparing the speed of travel in the copper wire and the soil. Just as a light beam bends when entering a glass of water. The signal travels faster in copper and "bends forward".
Note the three soil conditions good to poor conduction.
I'm off to gather some hurricane supplies. Will read the articles later .
Thanks for the article.
73

[pwdrive]

Here's an extract from Terman, Radio Engineers Handbook, concerning wave tilt:

"The electric vector of the wave produced at the surface of the earth by a vertical antenna possesses a slight forward tilt. As a result the electric vector has, in addition to the normal vertical component a slight horizontal component parallel to the surface of the earth, and lying in the direction of propagation. ... The component of the electric vector lying parallel to the earth's surface that is present because of wave tilt represents a voltage applied across earth's surface. This voltage causes a current to penetrate down into the earth."

It's explained in more detail in an article by G.W.O. Howe entitled Wireless Waves at The Earth's Surface in Wireless Engineering, Sept. 1940, P385:

http://www.americanradiohistory.com/...er-1940-09.pdf

So far as I can make out there it is, a horizontal component of the transmitted E field lying in the direction of propagation (the same direction as the wire in a Beverage antenna) due to the wave tilt and it's that, that results in the current flowing along the antenna wire.

Lawrence.

[reset]

 The article was written by JJ Carr who authored "The practical Antenna Handbook".  He shows the same picture in the book and offers this explanation.

   

Two observations of my own.
1. As he says the performance depends on the load resistor being well grounded. The incidence wave must be absorbed by the load resistor or there will be a reflected wave which will produce a standing wave which will decrease performance.
2. K is a velocity factor. Poor conduction causes a lower velocity which in turn increases the effective length of the antenna.

If you would like a copy of the book go here and click the fourth link down the page. The article reference is around page 230.
http://radio.radiotrician.org/2017/01/