For 160 I make my coils 6 inches dia. mainly... I usually aim for my coils to
come out roughly square, i.e. 6" dia. X 6" long... My rationale here is that
this gives the best Q with least dissipation, though it may be gilding the lily
a bit...
4 inch dia. will work also and thin wall PVC septic drain field tubing comes in
this size - so Lowes, etc... My 6 inch plug form is home made with end plugs
circle cut from plywood, 4 oak formers making the tube and then wrapped with
galvanized steel (heating duct) to get a nice round plug... If you know anyone
with a wood lathe ask them to turn a 6" X 12" plug for you...
Cebik, W4RNL, on his web site will have discussion of how to calculate coil
dimensions, i.e. length X turns for a given uH... There are other coil
calculators available on line, just do a search...
Wire size is depending upon the power you are running... #10 solid wire will
work nicely for traps and general matching.. #8 solid for series tuned coils
with more current flowing in it, high power contesting, etc... Since these are
spaced turns bare wire from stripping the insulation off THHN, Romex, or
similar, will work nicely... The easist way to strip wire is with a box
knife.. Clamp the end of the wire in a vice, hold the wire stretched with one
hand, hold the box knife almost parallel to the wire, then back up sliding the
wire through your hand as you slide the knife along the wire... 30 seconds of
practice will make you an expert...
I use quarter inch, dead soft, refrigeration copper tubing for my tuner coils -
even though I mostly contest CW in the low power catagory I get a percent or
two more efficiency - but when I do decide to run RTTY with the amp into a low
impedence antenna I don't have to worry about over heating.....
denny ... k8do
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