To: <amps@contesting.com>
> Date: Wed, 03 Jun 1998 07:36:50 +0100
> From: "Ian White, G3SEK" <G3SEK@ifwtech.demon.co.uk>
> Guessing at the length and diameter of a 5W resistor and using Tom's
> estiamte of "about five" turns, the usual formula for the inductance of
> a solenoid gives results somewhere in the right area. I wonder how well
> it works with the actual dimensions?
> Could you run a ruler over the resistors, Tom, and give us a better
> estimate of the actual number of turns?
Nope. The turns are .150 inch wide, and only fill a .68 inch long
area .278 inches in diameter. Being so wide, it's difficult to count
the exact turns because the starting and ending points occupy a large
portion of the diameter where they disappear under the end caps.
It looks like about 4-1/2 more or less turns.
I am certain, with about 0.5%, of the inductance. By the way that
inductance changes if I place the resistor near any other conductors.
These resistor would make VERY poor suppressor resistors, especially
for 3-500Z's where the self-oscillation frequency is in the 180 MHz
range with a directly grounded grid (and lower ~150-160 MHz with long
leads and capacitors, like in the SB-220).
73, Tom W8JI
w8ji.tom@MCIONE.com
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