I made a posting with a mistake, canceled it, and
am reposting. If the earlier posting got through,
please ignore it.
Jim Kelley wrote:
Cecil Moore wrote:
Jim Kelley wrote:
Cecil Moore wrote:
That makes the antenna a standing wave antenna.
It makes it an antenna.
Well, putting a load resistor on a coil is a lot like
a T2FD. :-) In fact, the way that a T2FD lowers the
50 ohm SWR is by reducing the reflections from that
load resistor.
Standing wave current has a negligible phase shift in
the coil or in the whip and therefore cannot be
used to measure the delay through a loading coil.
The delay through the coil depends on inductance and capacitance.
Yes, but the delay is not measurable using standing
wave current because standing wave current doesn't
change phase in a coil or in a wire. So far, all of
the phase measurements reported here have been using
standing wave current phase. Standing wave current
essentially doesn't change phase in a 1/4WL long
open-ended antenna.
To the best of my knowledge, all attempted phase
measurements reported on this newsgroup, on current
through a loading coil have been made using standing
wave current with its fixed phase. No useful coil
delay information can come from such measurements.
So your claim is that information about Bugcatcher coils with a load
resistor attached is more useful?
It is more useful for determining the delay through the
coil. If you were trying to measure the phase shift
through a 1/4WL stub, would you use the standing wave
current with its zero phase shift? Or would you terminate
the stub in its characteristic impedance and measure
the phase shift in the subsequent traveling wave?
Here are some recently generated graphics around which
I am going to put some words. Hopefully, they will
provide some stand alone information.
Given:
http://www.w5dxp.com/openstus.GIF
How would you determine the phase shift at any point
in the open stub?
Given:
http://www.w5dxp.com/termstus.GIF
How would you determine the phase shift at any point
in the terminated stub?
Note that the two stubs are identical except for one
being open and one being terminated so they have
identical traveling-wave phase shifts.
--
73, Cecil
http://www.w5dxp.com