RadioBanter - View Single Post

March 10th 06, 10:11 PM posted to rec.radio.amateur.antenna

wrote:
Please tell us all how you would measure the "traveling current" while
ignoring "standing wave current".

Good question. One would ideally do it in a system without
reflections. I am struggling with that concept right now.

The best thought I have come up with so far is simple:

coil
+----////----+
| |
source --- cap
| ---
| |
+--/\/\/\/\--+
resistor

I'm not a measurements guy so I could use some help.

What's wrong with just reporting the measured the delay
through your test coils? Your measured data already
shows the current on one side of the coil to be
different from the current on the other side of the
coil. All we have to worry about now is the delay
through the coils.

If I've got your attention, let me repeat something I
posted days ago.

The forward current through the coil can indeed be assumed
to be equal magnitude at both ends of the coil without much
error. That should make you happy.

The delay through the coil is whatever it is but it is
nowhere near zero. I assume that makes you unhappy.

The reflected current through the coil can indeed be
assumed to be equal magnitude at both ends of the coil
without much error. That should make you happy.

The delay through the coil is whatever it is but it is
nowhere near zero. I assume that makes you unhappy.

The standing wave is the phasor sum of the forward wave
and reflected wave. Its magnitude can vary from about
double the forward current at a current loop to close to
zero at a current node. I assume that makes you unhappy.

The standing wave phase is close to constant and fixed
near zero degrees within 1/4WL of the feedpoint. I assume
that makes you happy.

So three out of six results should make you happy and
that's about all any mere mortal can hope for. :-)
--
73, Cecil http://www.qsl.net/w5dxp