[Mobile-Portable] All on list please stand..........

[Tom Bates]

>>OK, guys.  I think we can quit before all three hundred members check in.  :)
73, Dick


All right then...I'll ask two serious on topic questions.

I need to wind a new shunt matching coil (coil placed right across the feedpoint) for
my 40M, centerloaded vertical.  At resonance, I measure an "X" of zero ohms, an "R"
of 24 ohms, and an SWR very close to 2:1 (where my 706 starts reducing output!).
This antenna is about 31 electrical degrees long, so I would expect to see something
in the range of 15-20 ohms Z plus (in this case) probably 5-9 ohms ground and other
loss. (Anyone please confirm or correct my thinking?)

Now, question 1.  How is the parallel L calculated?  I have just "guessed" in the
past and added or subtracted turns until R approached 50 ohms with X remaining at 0.
The coil I am using at the moment measures at 7.7 uh.  It is 20 T, #14 AWG, 1.375 dia
and 10 TPI wound on a "threaded in the lathe" delrin mounting form.  (This calculate
correct by anyone?)

Question 2.  Does anyone have one of those old cardboard Shure slide rules which
calculate coil data for sale or trade?  I have actual size JPEGs to homebrew both the
Shure and the Allied calculators (and will be happy to share), but would really like
to have the genuine article.

Thanks Gang, and  Happy Mobiling...

Tom   AA1NZ