Monday, February 21, 2011

2M + 70cm Open Sleeve Vertical Dipole


Johnny Pedersen (LA3AKA)

I was playing around with the MMANA Antenna analysis software and wanted to design a 2m/70cm vertical antenna. I tried different antenna models, J-pole, half wave dipoles, Ground Planes …. I then remembered a chapter in the 18. edition of the ARRL Antenna Handbook covering Open Sleeve antennas to make Broad band antennas. I thought that this might be useful for making a dual band VHF/UHF antenna.

0x01 graphic

The Antenna is planned built using 6mm aluminium rods. According to MMANA this will with a distance of 3.2cm between driven element and sleeve elements give an Feedpoint Impdance of 75 ohms on 2 meter and 50 ohms on 70cm. One nice thing with this antenna is that you get a good gain on 70 cm (approximately 3dB over a g Gain:

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