stacked primary \ winding direction bobs message attached this time

["steve" <stephen_crawshaw-at-tesla94.freeserve.co.uk> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

sorry forgot bob's message of Feb 99 (below)

steve


Bob said
hi all,
        I have been playing around with the  stacked primary idea and
have some
figures to throw about for those that are interested. I started with 12
turns on each coil with a total of 45 uh on each one. I then laid one of

the primarys on top of the other with the turns opposing each other
,this
made the total inductance 115 uH. I then turned the top coil over so
that
it is like a slice though the centre of the bottom coil, ie they are
mirror
images of each other. the minimum spacing between the two coils is
11/8"(32
MM) this results in a inductance of 30 uH. I then added 1 1/2"(38) of
spacing . This brought the inductance up to 45uH. I then checked how
many
turns this equated to and found it worked out at 3 turns. If my maths is

correct with a 0.01 cap this should give a tuning range of about 50 kHz.
A
useful range of tuning for 1.1/2" of movement. I don't know what to do
about finding the best position for coupling, and of course it might all

change when it is in the tank circuit rather than with 9 volts at 1 kc's

from my bridge. Any feedback most welcome. hope this makes sense.

regards
bob golding

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