On 8/31/2018 6:09 AM, Jim Thomson wrote:
## Are you sure about this ? I have used .25 edge wound rollers,
I am sure that flat conductors result in lower Q than round conductor.
I have done innumerable Q meter measurements to confirm this.
I didn't say that flat conductors don't work at all.
## I have also tried winding strap coils flat, like what you used to
see for a 10M tank coil.
That works superb for LOW amounts of uh. Then you can also minimize
the spacing between
adjacent turns. Typ used on 12-10-6m linear amp tank coils..and
What matters for inductor optimization is the winding PITCH, IE
the center to center distance between adjacent turns. In a strap
wound inductor, closing up the gap between the turns, at some point
exacerbates proximity effect and lowers Q. In any event, making
low value inductors is problematical; there is no way to get the same
Q that you would get at higher values, even if you use round conductors.
The only workaround AFAIK is to use 2 inductors in parallel,
each with twice the desired value, oriented so as to not
have much mutual inductance. Or use a single turn loop, over
a ground plane, to reduce inductance. Of course the ground plane
decreases Q, so nothing is free.
## I have had nothing but grief with tubing coils used in roller
Agreed, edge winding is a necessary evil for roller coils. But you
do pay for it with a Q reduction. Now that I have an Rig Expert
AA-55, I find that I can measure the antenna impedance and then
model the design with SimSmith, and finally build the
matching network on the bench with fixed inductors, and
then I don't need roller inductors out at the antenna, because
the matching network works the first time I try it. Just in case,
I can get a moderate amount of adjustability by using self supporting
coils (with the form removed) and then squeezing or spreading the
turns. Force 12 sells a motorized "Tornado" coil that does this.
Jim VE7RF
73
Rick N6RK
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