From: mystuffs@orwell.net (Metlicka Marc)
Date: Thu, 28 Dec 2000 04:08:59 -0500
Subject: [TSSP] coil measurements
paul,
i have completed resonant measurements on four of my coils for you. i
did as you suggested and used channel two for the trigger and measured
the base frequency with my fluke 1953a. pickup coil was 5' away and all
probe leads are run along the floor and separated with no crossing and
no power cords in the area.
these results are:
1: bare coil form dia. 3.514" (9-1 dh)
31.804" wound length
.020" wire dia., 24g, .0257 ohms per ft.
resistance of windings: 35.8 ohm ( with fluke 87III), 34.4 ohm ( with
ESI lcr bridge)
first res. V peak: 455.53 khz
ground to first winding: 13"
2: bare coil form dia. of 4.156" (10-1 dh)
42" wound length
.020" wire dia., 24g, .0257 ohm per foot
R of windings: 60 ohm (fluke 87III), 58.9 (ESI)
Vpeak res.: 277.4 khz (2nd) 712.3 khz
ground to first winding: 13"
3: bare coil form dia. of 8.75" (4.6-1 dh)
40.5" wound length
.0126" wire dia., 28g, .065 ohm per ft.
R of windings: 425 ohm (fluke), 423.4 ohm (ESI)
Vpeak res.: 61.9khz (2nd) 157.9 khz (3rd)229.7khz
(4th)294.4 khz (5th)355.6 khz
ground to first winding: 14"
4: bare coil dia. of 4.5" (6.7-1 dh)
30.25" wound length
.016" wire dia., 26g, .041 ohm per ft.
R of windings: 80 ohm
Vpeak res.: 237khz
ground to first winding: 12"
all measurements are taken with 5' of free space on all sides of the
coil and a seven foot cieling hieght, the coils sat on a poly milk crate
wich was placed in the middle of a ground plane aray pattern that was
sugested by paul. this being made of expanded aluminum "gutter guard"
placed in a double crossed pattern with 5 lengths 60" long and 8" wide
each. this is very nice stuff and i recomend it to anyone.
there was an interesting note with coil #4, this coil was not made by me
and the builder did a very fine job winding this coil with zero gaps in
the windings, it was finished with many coats of poly and is a very nice
coil.
it was sent to me because it would not perform at all for this person no
matter what was tried, when at first making my res. measurements i found
that i only got a resonation at 383khz and it was of less amplitude then
what was being put into it. after looking it over i noticed that he had
drilled two ajacent holes at the edge of each winding, top and bottom,
then looped the wire through and around these holes a couple times then
into the form for base conection and topload conections.
after i cut the wire out of these holes and unwraped one turn each, top
and bottom, it then acted and performed properly.
the only thing i can think of is that the little wraps through the holes
acted like little "chokes" inhibiting any hf action.
does anyone have any ideas on this?
i would now like to do the capacatance tests like terry has just shown
and any other testing that can be of help, readings with topload, or i
would love to make Q and coupling measuremnts on some of these if anyone
could be so kind as to offer an explenation?
hope some of this helps and i will keep pluging away blindly as time
goes on.
marc
ps. paul, the strange wave res. within the wave i mentioned only happens
when i drive the base with very low input frequencys. like the coil is
strugling to gain a resonant state? ideas?
i can send some pic's if it would help
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.