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Dear Paul,
In a nutshell:
- You can tune up more or less any bit of wire for
reasonable results on 500kHz. For best results, make it as high up as
possible, and secondarily as long as possible. An HF long wire, or dipole with
feeders strapped would be fine.
-Work out the capacitance of the wire (see formulas
on ON7YD's antennas pages). and calculate the inductance for resonance around
502.5kHz. For most HF-sized wire antennas, this will be of the order of 100s of
uH. The resulting coil is connected in series with the antenna downlead. It
needs to be adjustable because the resonance will be quite sharp. An earth
connection is required, preferably close to the downlead/loading coil - a
number of ground rods connected together is usually as good as
anything.
-For reception, that will work fine, for
transmission you also need to adjust the resistance match, either with a tapped
transformer, or with a tap on the loading coil itself. Some kind of impedance
bridge, SWR bridge etc. will be useful.
Good luck,
Cheers, Jim Moritz
73 de M0BMU
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