Richard.
You have no need to be sorry!
\You are trying to help me and
I appreciate that.
My problem started when I moved
away from a homebrew coil on a circuit
which was coupled to a rod ( distributed inductance)
The coupled rod when moved allowed for
an ideal matching setup
as it could be made into a perfect match
for top band use.( the rod was the driven element)
When I substituted a variometer for fine
tuning everything went to pot!
(That is why they call mesh circuits 'complex' )
Thus the questions regarding variometers
and the markings. With the new band in
the U.K. being used I suspect we are going
to hear a lot more about this instrument
and I can then reintroduce it on my antenna
Best regards
Art




(Richard Harrison) wrote in message ...
Art Unwin, KB9MZ wrote:
"Could you share with me a method of approximating the total inductance
together with its variance values?"

The design of shortwave coils is a complicated process. Skin effect
causes most loss, and single-strand wire wound as a single-layer coil is
usually best. According to Terman, the highest Q is usually, for a given
sized coil, gotten by a winding length somewhat less than the diameter
of the coil. Terman refers to an article in "Wireless Eng.", vol. 26,
page 179, June 1949 by G.W.O. Howe.

My big help with coils comes from the ARRL "L/C/F Calcululator", a
specialized slide-rule. My "Model A" has a price of $2.00 printed on it.

Tom Bruhns has done a lot of work with coils and knows much more about
them than I do. Maybe he will offer some help.

Reg has studied the pertinent factors and used them for some of his
marvelous programs, so he can be a big help.

Sorry I am not qualified to be much help. My method has been "cut and
try".

I was reading an excellent article from a 1920 QST as reprinted in
January 1966, by E.H. Armstrong about his Signal Corps research in WW-1.
He noted that his IF transformers benefitted from many turns of fine
wire which reduced capacitance and added enough resistance to dampen
oscillation tendencies. Armstrong was using "Type 5" triodes in his IF
amplifier of 100 KHz. I am sorry that I am so out of date.

Best regards, Richard Harrison, KB5WZI