Where is the positive and negative on a telescopic antenna?

Question

Where is the positive and negative on a telescopic antenna? The image below (from a previous stack exchange question) shows a dipole antenna's positive and negative.

Can someone please post a similar picture, but for a telescopic antenna which shows where the positive and negative are for a telescopic antenna?

@user_1818839 Don't write _answers_ in the comment section. You have now made every other answer redundant but OP can not mark it as accepted. — pipe, May 19 '22 at 13:55
Isn't it the same thing as your diagram except the one half is imaginary behind a ground plane? — DKNguyen, May 19 '22 at 14:26

score 5 · Answer 1 · answered May 19 '22 at 14:29

By grounding one end of the half wave dipole antenna shown in the question, one can obtain a quarter wave monopole antenna.

And a whip antenna (including telescopic antenna) is a type of monopole antenna.

So just cover the half of the gif with your hand and you'll get the radiation of a whip (or a telescopic) antenna.

The polarisation changes from horizontal to vertical, though.

Andy aka · Answer 2 · 2022-05-19T16:46:54.583

Halfway between left and right halves of the \$1/2 \lambda\$ dipole is a point in space that has zero electric field. This is shown by the green line in the picture below: -

So, you can discard 50% of the dipole antenna and drive the remaining 50% with respect to a ground-plane (formed from the green line above): -

The above images from this answer with a fuller explanation (and quite possibly where the image in the question came from).

This new antenna is known as a monopole and, a telescopic antenna is a monopole. The ground-plane need not be a full-plane and can be formed by the body of a radio receiver and the presence of a human body (in the case of a walkie talkie) or from a counterpoise like this: -

Image from this useful document on antennas

Where is the positive and negative on a telescopic antenna?

2 Answers2