Sleeve Antenna

[gjo]

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?

 

[vfone]

The main difference between sleeve antennas and single wire or whip antennas, is that the sleeve antenna use parasitic elements.
The spacing and size of those parasitic elements can be tuned to get best performances for radiation, VSWR, and bandwidth.

 

[FvM]

"Sleeve antenna" is an somehow ambigous term used for different antenna geometries. Well designed sleeve antennas are halfwave dipoles, respectively less depending on the ground geometry than a quarterwave monopole does.

It should be noted that some whip antennas with coaxial connector, e.g. for WiFi frequencies are actually halfwave dipoles with center feed, quite similar to sleeve a antenna.

 

[gjo]

The main difference between sleeve antennas and single wire or whip antennas, is that the sleeve antenna use parasitic elements.
The spacing and size of those parasitic elements can be tuned to get best performances for radiation, VSWR, and bandwidth.

Hi, thanks for the reply. When you say that the parasitic elements can be tuned, do you mean to lengthen or shorten the sleeve?

--- Updated Oct 10, 2020 ---

"Sleeve antenna" is an somehow ambigous term used for different antenna geometries. Well designed sleeve antennas are halfwave dipoles, respectively less depending on the ground geometry than a quarterwave monopole does.

It should be noted that some whip antennas with coaxial connector, e.g. for WiFi frequencies are actually halfwave dipoles with center feed, quite similar to sleeve a antenna.

Hi, thanks for the response. I thought that the sleeve is attached to the ground with which combines with it to form the parasitic elements?

 

[vfone]

Yes, as I mentioned, tuning means changing (more or less) the length of the sleeves (arms) of the antenna, and also the distance between them and the antenna.
If for the antenna is used a λ/4 ground plane antenna, the sleeves are connected to the ground, but if the antenna is a λ/2 dipole, the sleeves are not connected to the ground.

https://www.eham.net/data/articles/8808/index0.jpg

 

[FvM]

The explanation seems to support my request for clarifying which type of sleeve antenna you are exactly talking about.

A λ/4 antenna with a ground connected sleeve is in case of doubt acting as a λ/2 dipole.

 

[gjo]

Yes, as I mentioned, tuning means changing (more or less) the length of the sleeves (arms) of the antenna, and also the distance between them and the antenna.
If for the antenna is used a λ/4 ground plane antenna, the sleeves are connected to the ground, but if the antenna is a λ/2 dipole, the sleeves are not connected to the ground.

https://www.eham.net/data/articles/8808/index0.jpg

Ok, got it. I understand now. Your help was very useful. Thanks.

 

[Azulykit]

I have always liked sleeved antennas. The primarily interest is that the addition of a sleeve allows one to significantly increase the antenna bandwidth. I have less than stellar success when I tried to "shorten" an antenna with a sleeve but the bandwidth increase can be very useful.

Sleeves can be used with monopoles and dipoles. They are also seen occasionally with printed circuit versions of either.

A search of the web turns up numerous citations on the subject. I got a kick out of the Coke can based antenna.

 

[davenn]

Hi, thanks for the reply. When you say that the parasitic elements can be tuned, do you mean to lengthen or shorten the sleeve?

--- Updated Oct 10, 2020 ---

Hi, thanks for the response. I thought that the sleeve is attached to the ground with which combines with it to form the parasitic elements?

No, it is as FvM stated