Base Station Aerial for 2M & 70CMS

Firstly I take no credit for the design of this aerial - its been around for a very long time and in fact was used in the very early days of VHF two way radio telephones and marine operations - so it works.

It’s simply a sleeve dipole or “bazooka” dipole, no nothing to do with that American chewing gum of years ago either.

I’ve played around using RG-58U 50ohm coaxial cable and also the very cheap TV 75ohm coax, which didn’t have any identification markings on it. Surprisingly the 75ohm coax gave better results with a slightly lower SWR.

I suppose the acid test is does it perform well on receive and how well does it transmit your RF power out to the distant stations. With the aerial I built (cheap TV 75ohm coax) on test 5 feet above the ground I was able to access 18 repeaters on 2M. Some of the repeater signals were only just breaking the squelch but I was still able to access 100% with my 10 watts of RF power - so pleased with that. I tested it on 70cms and achieved a low SWR but unfortunately not in the capture area of any UHF repeaters so cannot comment on it’s receive or transmit capabilities.

So lets make it - firstly run the coaxial cable from your radio shack to the aerial support location. Now you are ready to build the aerial from the coax feeder. Simply measure back from the end 21 inches and cut through the outer plastic. Now roll back the copper braid over the coax cable for 14 inches down the cable run and tape to fix in place. Now with kitchen metal foil cover the 14 inches of copper braid, this forms the “bazooka” balun. You then slide the whole thing into a plastic tube with a cap on the top for weather proofing. Use a cable tie to secure the coax at the base of the tube to stop the aerial falling out and that’s it - a base aerial for both 2M and 70cms!

IZ0JUB & GW4CBR

Supporting each other in the true spirit of amateur radio.

Thank's go to Mike for sending the design, watch this space for more to come

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