Just for fun this morning I tried WSPRing on 7MHz using JUST a ferrite rod wound coil and a 365pF tuning capacitor as a tiny loop antenna sitting on the desk. All other antennas and grounds were disconnected fully. I used one of the low tap positions to find a 1:1 SWR position and put the FT817 on 5W. The rod did not get warm. The wire used is around 0.5mm enamelled copper with around 60 turns, tapped at every few turns at the cold end.
The ERP was very small, although I have not yet measured it. To my total amazement, I got an immediate -24dB S/N WSPR report from OZ7IT in Denmark at 853km. Just proves how incredible WSPR is and what a powerful tool it is for simple experiments like this.
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The ERP was very small, although I have not yet measured it. To my total amazement, I got an immediate -24dB S/N WSPR report from OZ7IT in Denmark at 853km. Just proves how incredible WSPR is and what a powerful tool it is for simple experiments like this.
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| Ferrite rod TX antenna on 7MHz WSPR - it worked! |
