On Mon, 7 Jan 2008 18:26:16 -0500, "AI4QJ" wrote:


"Richard Clark" wrote in message

Now, if you would simply take my advice to heart: strip away the
static and ask the question that is plaguing you.

OK. Thank you for your patience. You said "The SWR on the wire is load-
based and is equal to 8:1 as evidenced by CURRENT on the wire. :-)

Hi Dan,

Well, in fact I don't recall having said anything about "Load-Based,"
but it is immaterial to your question(s).

You cannot make a SWR measurement on a receive antenna any other way."

You are still trapped in a loose thread of associations.

We will get back to that in a moment (I hate doing this, trying to
intuit what you are after). The specific comment you recite above is
wholly out of context, and is being joined to a new one. This is why
I ask you to strip out the noise and ask the question that is
bothering you.

My very simple question: How do I measure that ISWR current?

Specifically, as you have already suggested, with a loop pickup.
However, in my career I have never encountered its use as a precision
device when measuring voltage is so much easier. EZNEC does not
report voltage (although it could be computed, I will leave that to
others as there is no significant information obtained in that
exercise).

Please describe possible meters and probes and where on the receive antenna
do I measure this current?

I've commented on that already. But this tied back into receive and
you will not find a satisfactory, bench answer for that which is
practical (in the sense of $).

At the input?

For waves on a line you go to the line. EZNEC provides this quite
clearly and even provides a graphic solution if you are not into the
actual numbers.

At the nodes? At the zero crosses?
How do you calculate ISWR? Is it Imax/Imin?

That is the conventional way to observe Standing Waves.

I am only trying to
conceptualize what you mean. Do you have to block the reverse current
somehow and measure forward current and vice versa? What does this do to the
standing wave? What does any direct current measurement do to the ISWR
itself?

Dan, you've got yourself wrapped around the axle and here I have to
force a solution to your problem that you only vaguely offer through a
chain of disconnected references above.

First, you spend an inordinate amount of effort quoting to the point
of receiving, and yet none of your questions appear to be aware of the
significance of receiving with these breed of (Traveling Wave)
antennas.

Cecil's wire, one foot off the ground, is strongly influenced by its
proximity. I demonstrated that. However, Cecil divorces this effect
while embracing his goal of explaining away the confusion about
Traveling Wave antennas. This one foot high monstrosity is most
closely allied with the Beverage antenna which was developed with
ground in mind and even here, Cecil corrupts this concept to turn his
model into a Traveling Wave transmission line. In effect, his is a
bait and switch argument as he abandoned the "explanation" 350 posts
ago and never returned until I forced the argument.

Cecil, under protest to my proofs of Standing Wave on these Traveling
Wave, then supplied a citation that heads this very thread:
"Because the Beverage is a
traveling wave, terminated antenna, it has no standing
waves resulting from radio signals."

It contains FROM radio signals. FROM is an externality. In other
words the antenna must be externally excited to test the validity of
this specific statement. Further, this statement has its own internal
logic in that the antenna (the Beverage) is a RECEIVE antenna.
Further, this statement has its own internal logic in that a Beverage
antenna employs ground as an active element. Hence, all internal
logical characteristics are consistent with the statement about
externality. Any reference to source SWR is wholly inappropriate.

EZNEC is perfectly capable of measuring a receive antenna, if you can
supply an antenna to excite it. I did so explicitly. The reports
offered by EZNEC will give you a source SWR reading like Cecil quoted,
but that is entirely unrelated to the receive antenna performance. I
did not report that reading for that reason, Cecil did - for whatever
reason, but a reason that bore no relation to Standing/Traveling waves
on the test antenna.

EZNEC will report all currents on all wires everywhere. When the
Beverage is excited by a source 100 kilometers away, those currents in
the wires defining the Beverage exhibit classic Standing Waves. This
is quite simple.

Now as to your enquiry in how to measure those currents. That is not
practical at the nanoAmpere levels, but software does it quite easily.
If I were tasked to do it, I would immediately transform this into the
voltage model, modulate the source with an unique pattern, and perform
a synchronous detection of the levels involved along the length of the
line. A trivial concept that is difficult in practice.

Now, I have pounded out a lot of words in an effort to eke out your
question. Was it answered?

73's
Richard Clark, KB7QHC