Christer Andersson wrote:

Hello (V)LF experimenters,

I have an idea of resonating my existing vertical on 8 kHz.
Is there a practical way to construct a 600 mH loading coil, withstanding 3-4 A 
and high voltage?
Any *large* toroids on the market?'

/Christer
sm6pxj

Chris.
Look around for an old high power AM modulation transformer or choke. You might 
need a lot of them
!!!! otherwise air wound coils would probably better. LF toroids are a 
possibility for low power. Try
a mains variac as a substitute for a variometer !!!!! it might do something, 
maybe lossy at 8 khz.
G3KEV