Wednesday, June 29, 2016

Directional Medium Wave short antenna

The quest is for a Medium Wave antenna that doesn't have to be 800 feet long with directional characteristic. Also a chance to learn more about the EZNEC program. This is not and original work. Different parts were gleaned from several sources.

This is the start point. Only 25' long should be doable at most any homestead. An apartment dweller could scale it down and mount it on a wall?
I'm working on an outside antenna so I scaled it up up 16' X 29'.
the transformer is 50Ohm to 900Ohm. More on this later.
I put the model in the EZNEC and here are the results.
It is directional and relative small.
A different view of the pattern

A 3D view from overhead.
What about the SWR?
Sweep from 0.5Mhz to 1.5Mhz looks pretty good.
What about that transformer?
FT50-43 with 7 turns primary and 30 turns secondary should be good. I worked this one out at a friends request and to learn to use NEC programming. Looks like one I may have to try.
One final note the 900Ohm resistor could be from 500Ohm to 1000Ohm range and could be an adjustable as in the first drawing.

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