can coupling be too high

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Original poster: "colin.heath4 by way of Terry Fritz <teslalist-at-qwest-dot-net>" <colin.heath4-at-ntlworld-dot-com>

hi all,
         i have a question regarding coupling.here goes.
when we couple a coil tightly problems such as racing sparks appear so we
drop off the coupling. but why? does coupling too tight really affect the
performance badly? it is often stated that a coil too tightly coupled will
take on transformer action. i dont know if this is an old school of thought
or still applies.
i have experianced it with my small 2" coil but im not sure wether this was
due too the coil not being optimised for tight coupling perhaps ruining the
quenching of the gap.
should we be working on better insulation on our secondarys rather than
working around the problem ?
many thanks
colin heath