[hpsdr] Proposal for Loop Anntenna

[Guido]

The intention was to make a loop for 7Mhz. So, found a few sheets of
polystyrene and glued them together so that one large rectangular board was
created with dimensions of 1.5m x 1.5m x 0.04m. Took a long sheet of
aluminum foil with a width of about 0.3m. Since the foil has thickness of
0.02 mm i felt it was to thin for my purpose, so I folded it once in the
hope to make it thick enough for the skin effect. This sheet was wrapped
around the the board, where the ends of foil meet each on the top of the
rectangle, and where the width created some U formed shape.  I really did
not want to introduce resistance, so made it of once whole piece of sheet.
The ends of the sheet were isolated with paper, to make a capacitor of it.
About 0.2m of the ends are overlapping to create this capacitor. I cut some
line in the polystyrene, to get the two ends firmly together and in such way
that they are movable. This capacitor idea works, but for fine tuning I
really required an additional small variable capacitor.

Once tuned in 7Mhz band, I could see with Rocky that the bandwidth of the
loop was about a few 10s of kHz. Too broad for a good efficiency I thought.
A have to say that at that time the weather was to bad to go outside, so I
tested only inside the house, and there are other metal objects in the
neighborhood that could have interfered.

But my feeling is that the foil is also to thin. Should I have connected the
ends of the U formed shape, would that optimize the performance?

Actually it was a nice experiment, any ideas for improvement?
Guido
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