Sleeve Antenna

gjo

Joined May 22, 2013
30
Why when sleeve antennas are used for high frequencies they are superior to single wire or regular whip antennas in both vertical pattern and impedance characteristics. I don't understand when it states the impedance characteristics of a sleeve Antenna can attain satisfactory standing wave ratios over a wider range and radiation at low angles is much greater than a whip?

Papabravo

Joined Feb 24, 2006
14,677
Why when sleeve antennas are used for high frequencies they are superior to single wire or regular whip antennas in both vertical pattern and impedance characteristics. I don't understand when it states the impedance characteristics of a sleeve Antenna can attain satisfactory standing wave ratios over a wider range and radiation at low angles is much greater than a whip?
The elements of an antenna interact with ground to produce a radiation pattern in three dimensions. Over some range of frequencies an RF signal will be efficiently transmitted or received. How this happens is determined by the geometry and dimensions of the antenna.

For a given antenna, at a given frequency, the characteristic impedance and the standing wave ratio tell you something about how much RF energy is radiated (what you want) and how much energy is reflected back to the source (what you don't want). When an antenna radiates energy at a low angle with respect to the surface of the Earth it just means that very little of the energy is being directed off into space; to Alpha Centauri perhaps.

gjo

Joined May 22, 2013
30
The elements of an antenna interact with ground to produce a radiation pattern in three dimensions. Over some range of frequencies an RF signal will be efficiently transmitted or received. How this happens is determined by the geometry and dimensions of the antenna.

For a given antenna, at a given frequency, the characteristic impedance and the standing wave ratio tell you something about how much RF energy is radiated (what you want) and how much energy is reflected back to the source (what you don't want). When an antenna radiates energy at a low angle with respect to the surface of the Earth it just means that very little of the energy is being directed off into space; to Alpha Centauri perhaps.
Thanks for the response, but why does the Sleeve Antenna radiate at a low angle. And why are they efficient over a wide range of frequencies?

nsaspook

Joined Aug 27, 2009
7,733
You don't need exact resonance for an efficient antenna. What you need is a closer antenna radiation resistance match over a wider range of frequencies to match the antenna to space. When the incoming power moves into space the effect is resistive to the RF source and results in a lower SWR across the band in a matching system. As for low angle that's a distribution of charge current density canceling and reinforcing in the antennas physical elements as it radiates.

Some interesting history of the Sleeve Antenna.
https://www.cryptomuseum.com/covert/bugs/ec/sleevex/index.htm