Richard Clark wrote:
On Wed, 15 Mar 2006 22:42:55 GMT, Cecil Moore wrote:
The VF of my 75m bugcatcher coil calculates out to be
VF = 0.0175 at 6.6 MHz

On Fri, 10 Mar 2006 13:35:14 GMT, Cecil Moore wrote:

I'm willing to bet that my 75m
bugcatcher coil has at least a 40 nanosecond delay on 4 MHz
which is a 60 degree current phase shift.

On Wed, 15 Mar 2006 18:03:28 GMT, Cecil Moore wrote:

The coil data is: ~6" dia, ~6.7" long, 26.5 T, seems
very close to 4 TPI. Looks to be #14 solid wire.

Total turns 26.5
Through total turns, total wire appears to be 505"

With nothing offered in the way of inductance, from calculations it
appears to be 72.9 µH

With nothing offered in the way of distributed capacitance, from
calculations it appears to be 8pF

On Tue, 14 Mar 2006 04:09:08 +0000 (UTC), "Reg Edwards"
wrote:
V = 1 / Sqrt( L * C ) metres per second,
where L and C are henrys and farads per metre respectively. The
formula for L and C can be found in your Bibles from coil dimensions,
numbers of turns, etc.

V = 1 / Sqrt (5.88 * 72.9* 10^-6 * 8 * 10^-12) meters per second

where the 5.88 is to correct for per meter computations

it follows that V must then be 17.1 million meters per second

The velocity factor = V / c
Vf = 0.057
and Zo = Sqr( L / C ).
Zo = Sqrt (72.9* 10^-6 / 8 * 10^-12)

3 KOhms
. . .

This is a misapplication of transmission line formulas. The "C" in those
formulas is the shunt capacitance per unit length between the
conductors, not a series or longitudinal capacitance as used here. In
order to use the transmission line formulas, you have to have a second
conductor and determine the C per unit length between the two
conductors. Otherwise, you (or Cecil) have to come up with some other
equations. Some of the more picky of us readers will of course then ask
for the source and/or derivation of those other equations.

Roy Lewallen, W7EL