IEd Fong DBJ1 Dual Band antenna construction.

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tried to purchase one of these antennas from Ed in the USA, but unfortunately, they don’t ship out international, so I decided to build one. Firstly, I must say, yes, it is cheap to build if you don’t take into account the cost of 300ohm twin lead in Australia, I had to purchase 15 meters of it, just to use a meter of so.

 

I would like to share what I used to build the antenna. The first obstacle, was to try and source the pressure pipe (PCV) that was close to the class 200 that is readily available in the USA. All the plans on the net regarding the build states that the dimensions for all parts is based on one part on the dielectric of the class 200 pipe. I found our 20mm pressure pipe (available in Bunnings) was just a few decimal millimetres different to the class 200 spec.

 

The pressure pipe from Bunnings and two end caps, the 300ohm twin, a SO239 chassis mount and some RG8 coax and I ready to go. I had to recalculate the length of RG8 for the decoupling stub in relation to the velocity factor of the coax used. I cut it a bit longer and adjust for SWR at the desired freq. This brings me an important construction point, I checked the SWR at each stage of the construction with the antenna inside the pvc pressure pipe.

 

I made the free section at the bottom of the antenna a bit longer, because I wanted to build a base for the antenna, as shown in the image below. I have also included the images of both VHF & UHF SWR plot from my nano vna.