Sleeve Antenna

[gjoo]

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?

 

[Nanren888]

Been a while since I've been in that area. "Sleeve antenna" is a general term covering quite a number of implementations.
Generally, though you are making a dipole by using something, such as coax outer as the side opposite the coax centre.
A standard whip I guess is a monopole. To get radiation at horizontal it relies on reflection in the groundplane. With an infinite groundplane the reflection fills a virtual other pole and looks just like a dipole. With small groundplane the pattern at horizontal is less, so the pattern appearts to lift up.
.
The impedance of a monopole is different form that of a dipole. Maybe one of the experienced RF/antenna guys will fill in an impedance and SWR explanation for you.

 

[gjoo]

Appreciate your response. Your information got me thinking, I think I'm starting to understand what they mean by the ground radiation in this case. Thanks

 

[bertus]

Hello,

There are some antenna books from the ARRL on the internet archive:
https://archive.org/details/TheArrlAntennaBook
https://archive.org/details/fea_ARRL_Basic_Antennas

A lot of theory and practical information can be found in them.

Bertus