Multiband Sleeve Dipole

The open sleeve dipole is a most interesting antenna in that only one of the three dipoles are connected and fed with the feedline. The other two dipoles are benign and go along for the free ride. I used this system for several year ago for a WARC Band dipole and the results are the same as if I had used separately fed dipoles. The antenna is about 15 metres long and the spacing of the dipoles is 5cm (2”) the plastic spreaders can be any material such as 12mm plastic tubing with three holes drilled into them and the antennas are threaded through the holes. A simple piece of small diameter copper wire threaded around the main 30M dipole and around the plastic tube holds the spreaders from moving up the antenna. Each antenna has the standard “egg” insulator at the end.

I used polypropylene rope to hold the ends of each dipole out to the end sport which is 12mm aluminium tubing. The antenna was set up a few meters off the ground tied to one side of the house and a tree about 15M away from the house and then coupled the MFJ Antenna analyzer to it and the dipoles using the standard dipole formula were fairly close. A bit of trimming of lengths brought them very close to where I wanted to operate in the three bands. The antennas went higher in frequency by about 50 to 80 khz when the antenna was hauled up to the top of the tower.

Does it work. Yes. Exactly like three separate dipoles with no interaction between the bands. I used a 30M/17M vertical loop for a few years and this dipole setup works exactly like the loop. If there is 1 or 2 db difference, I do not notice the difference. The antenna exhibits a definite increase in gain and noise over other comparative dipoles cut for other bands. For example. If I listen to the 30M band on my 40M separate dipole and then switch to this 30M antenna, the noise and the signals increase. The same is true for the 17 and 12M bands.

My results are 214 countries on 30M, 142 countries on 17M and 68 countries on 12M. If I compare my 17M ability to work DX with another local ham about 2 km from me who is using a well tuned 3 el yagi then I am in the hunt after he works the DX first. On very weak signals that he will hear… I don’t. But that is the difference between a 3el yagi and a dipole.

I can’t supply gain graphs and charts. I have no way of measuring gain or losses and I cannot plot the patterns. To be sure… they will be very similar to standard dipoles because that is exactly what they are. It sure is convenient to be able to work all three bands with no switching and have an SWR of less than 1.5 to 1. There is no reason why the same technique could not be applied to other combinations such as 40M/30M/17M. I am planning to put another on up in the near future cut for 3.5 mHz and the second antenna cut for 3,8 mHz which will give me good SWR readings on both ends of the band and that solves the traditional problems of antennas in that band.

73 de Lee ZL2AL