On <9KHz there is only the need for a transformation to an impedance range say 
below 100 Ohm so that voltages are not to high and currents are not to high. 1 
Ohm is to less i mean, unless the primary coil is not fed directly through the 
output transformer; so the PA is directly placed at the loading coil. That may 
be problematic due to the high E-fields, so better spend some meters of 
standard loudspeaker cable and keep the PA apart from the coil . The region of 
50 to 100Ohm is a good choice. Transforming to 50 Ohm is necessary if there are 
measuring devices that work properly in this impedance region, such as 5 pole 
low pass filters or swr meters. But most of us will start just with an antenna 
in resonance and maximum antenna current, the PA will give.

Normally tapping is one way for matching. But on VLF the L will be extreme and 
so one can just choose small wires. Therefore it is better to use a inductive 
coupled primary coil out of bigger wire since there will be much higher 
currents in the primary impedance level.

But that are the basics and we all know them from LF so there might be just 
some missunderstandings here ;-)

Stefan/DK7FC

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