Date: Wed, 27 Feb 2019 11:12:37 -0800 (PST)
From: terry burge <ki7m@comcast.net>
To: Jim Thomson <jim.thom@telus.net>, towertalk@contesting.com
Subject: Re: [TowerTalk] OT: Inductor Calculator
<It just seems for TV stuff. Could not seem to get anything to work for a large
coil for 160 mtrs made of copper tubing?
<Terry
<KI7M
## It gets a lot worse. K6STIs latest version called ..coil 3.44 isnt even
close to reality ! Doesnt work, dont use it.
## I looked at steve, VE6WZs screen shots of the original k6sti coil
program from the 90s... and that
was for the oem cush craft 40 m coils. They consist of 68 turns of 12
gauge magnet wire, wound butt tight, on a
.75 inch solid fiberglass form. OLD coil program depicts 15.076 uh for
a single coil. Steve has a pix on his site with the MFJ
across the coil, and mfj depicts 15.114 uh...close enough.
## stuffing the identical 68 turns of 12 gauge magnet wire, wound tight, on
the same .75 inch solid fiberglass form, the new ..coil 3.44
software depicts just 8.549 uh which is clearly incorrect. And yes,
I entered it correctly, same lead lengths, and same length.
## I then tested the new coil 3.44 program on known stuff I have in the
shop.... its out to lunch, not even close to reality.
Thats using either of my 2 x B+K digital LCR meters, and also my
MFJ-259B. I tested several coils, both tubing types,
and also wire types like a half dozen air dux coils.
## also baffling, is the Q on the old coil software , on the oem 40m cush
craft coil is shown as just 81.
On the new coil 3.44 software, Q is depicted as a lot higher, like 252.
## Ok, fine, BUT..when comparing large tubing coils, like the .375 inch OD
silver plated copper tubing variety, .... on the old software,
they show up as sky high Q, like 1920. On the new software, Q is down
to 1230. This is on 7 mhz.
## Not only is the uh way outa whack on the new coil 3.44 software, the Q
is way higher for small wire wound coils....... and way lower for
tubing coils..go figure.
## Forget Q for a minute, thats semantics. Copper tubing is a helluva lot
higher Q vs aluminum tubing, for the same OD tubing...period.
Same deal with copper wire vs aluminum wire...for the same gauge. Dont
believe me, try winding an aluminum tubing coil, identical to whats
in a hb linear amp, then compare the difference. The aluminum coil will run
a helluva lot hotter.
## If you want to get real close with calculated uh values, use any of the
other popular coil calculators that can be found on line... most will
come out extremely close to what I measure on a LCR meter.
Jim VE7RF
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