MORE BENCH WORK REGARDING Permeability Tuned Coils..
(larger coils to tune antennas).
The GLUESTICK Coil (as used in my R7 style vertical project) explained.
Here is the gluestick coil on the
bench being tested with a
commercial coil. You can plainly
see the top uses T50-6 cores and
the main body uses the larger
T80-6 cores. IF YOU LOOK REALLY
CLOSELY you will see at the
bottom of the torroid stack a
yellow taped core (which is the
ferrite jumbo bead). I wrapped it in
yellow tape. The idea of the ferrite
was to give the inductance a final
extra "kick" right near the end of
adjustment.
This coil was plucked from an old
base loaded vertical. The Vertical
was about 26 ft high +/-. You can
see on the left side a green wire
with a tap on the coil.
The coil was adjusted to resonate
on one band...one frequency at a
time. I think the vertical probably
covered 80 through 10 meters. I
measured the inductance as 36.9
microhenries with my Autek RF1
Analyst.
This is a powered iron core slug (2 inches in diameter) consisting of 5 T-200-2
toroidal cores stacked and held together with electrical tape. Up here in Canada;
these cores cost us about $10.00 each..so this is a rather expensive slug!!
This slug will be wrapped in paper and inserted in the 36.9 microhenry air core
coil. The resulting increase in inductance will be noted. The results will be
applied towards my work with permeability tuned antennas.
Slug is inserted in the COIL over half way
and the inductance is measured on the
RF Analyst as 61.4 microhenries. An
increase of 24.5 uh. A very useful
increase.
Test frequency is 2.077 MHZ during
this test. The Analyst will go down to
1.7 mhz or so and up over 32 mhz.
There can be a 5% to 10% errror..but
for general work this is acceptable.
The error percentage is
repeatable..which means you can
factor that into your measurements if
you find out the error % of your meter.
MAXIMUM INDUCTANCE WAS 77 UH
WITH THE SLUG FULLY INSERTED
INTO THE COIL. THE ORIGINAL
INDUCTANCE WAS 36.9. THE
INDUCTANCE WAS DOUBLED AND
THEN SOME.
If this inductor was used to tune
the antenna on 80 meters; fully
inserted coil slug could then
perhaps get the antenna to tune
on 160 meters..or pretty close
perhaps. A remote slow turning
motor and a threaded rod so that
the core could be inserted
gradually would allow the tuning of
a vertical antenna; similar to the
way the popular SCREWDRIVER
MOBILE ANTENNAS ARE TUNED.
NOTE: I placed the big slug
(consisting of 5 stacked T200-2
torroidal forms) into a roll of paper.
You can see the paper and the
core inside the coil in this picture.
As a later modification to my glue stick coil..I added a ferrite core at the bottom
of the stack of powdered iron cores. What this ferrite core did..was to add a
greater amount of permeability to the core..right near the end of the adjustment
(core fully inserted out from the glue stick into the coil).
April 2008 update on the
T200-2 torroid cores..(the
big red ones).

W8DIZ or the torroid king
can sell you these with a
reduction in price as the
quantity goes up.

For Canadians..(like me)
(VE3AB)..the price will be
better now in 2007/2008
because our canadian
dollar is either on par
with the american $ or is
better than the green
back (slightly).
Above..my glue stick tweaker coil. It can move
the resonant frequency of the vertical antenna.
Better than cut and trim!

I simply wound about 5 turns of aluminum
ground wire over the glue stick coil.

I interfaced it with the R7 style vertical element
of my 20 meter mono band vertical.

THIS LASHED UP VERTICAL WAS FOR FIELD DAY
IN 2005.
NAVIGATION LINK BACK TO MY HAM RADIO
START PAGE
My R7 style vertical antenna (my experimental lash up 20 meter "no
radials vertical" pages ..can be accessed by this LINK HERE