Only just saw the postings re Decca coil screening.
My Decca pal tells me he lined Decca Tx coil huts with copper (thin - 20g)
to maintain constant dielectric environment and constant phase. The whole
operation of Decca depended on maintaining accurate phase. Note - NOT
grounded. Unlined huts caused considerable losses and phase shifts when wet
outside. Timber huts used in N. Canada not too bad in winter when dry but
lossy in summer when wet. VE's take note. Absolutely essential that proper
bonding maintained between sheets - solder not screws. Does NOT cause
losses if not grounded. Unimportant for amateurs because phase shifts don't
matter, although if out in the open a conductive box around coil could
prevent nearby wet bushes catching fire.
A point about corona. Electrical discharge off a point can exist without
being visible.
I referred some time ago to the "green" edition of Terman for coil data.
This referred to the 1943 edition of Terman - the one before transistors
got in.
I gather that when medium-wave went commercial in the UK back in the 60's
copies of this edition were fetching £100 a time.
Walter G3JKV.
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