Jim Kelley wrote:
Here is a photograph of a directional wattmeter converted to measure
current on W8JI's web page.
http://www.w8ji.com/building_a_current_meter.htm

IT DOES NOT MEASURE FORWARD AND REFLECTED CURRENT!
IT ONLY MEASURES TOTAL RF CURRENT!

That's exactly why w8ji "measured" a 3 nS delay
through a 100 turn, 10 TPI, 2" dia loading coil.

Dr. Corum's formulas predicts a velocity factor
of 0.033 on 4 MHz for w8ji's coil. That would
make it 37 degrees long with a delay of 26 nS.

W8JI "measured" a 3 nS delay because the standing
wave current that he used for the measurement
does not change phase relative to the source
phase in a wire or in a coil.

Do you really believe that RF current can travel
through 53 feet of coiled wire in 3 nS? Doesn't
26 nS make a lot more technical sense?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

wrote:
From other postings I've read I take Jim to be a pretty knowledgeable
guy - so this has to be a wind-up, right?

Steve, there are a handful of people on this newsgroup
who will stoop to anything to defend W8JI's 3 nS delay
through a 75m loading coil. It's a lot like a barnyard
pecking order devoid of technical content where the
laws of physics don't seem to matter at all.

I would be glad to step aside and let you shoulder the
technical side of the argument. It would be interesting
to see if the powers that be would expose a newcomer
to the same ad hominem attacks and obfuscation as they
heap upon an old-timer like me.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

On May 1, 3:55*pm, Cecil Moore wrote:
Jim Kelley wrote:
Cecil Moore wrote:

We would make a measurement of either the forward or the reflected
traveling wave, which are phase delayed along the antenna.

I'm sorry, but that is a false statement. Measuring the forward
or reflected traveling wave, which is less than 10% of the
total energy *on the antenna*, is exactly what is the problem.

Hmmmm. *Perhaps I misspoke. *I should have said that's what I usually
measure when I want to know how much power my antenna is radiating. *I
guess I don't actually know for sure what other people usually measure.
But if they have a Bird wattmeter for example, that's what they usually
measure too.

The context, as proved by your first posting above is
measurements "along the antenna". Why do you need to divert
the issue by changing the context in midstream? Why can't
you just discuss things in context?

A Bird wattmeter will not work "along the antenna". Contrary
to what you assert above, *nobody* uses a Bird wattmeter
"along the antenna" to measure anything. A Bird wattmeter
is a 4-terminal device requiring a reference which doesn't
exist "along the antenna".

The only measurements that have been made "along the antenna"
are total current measurements. Seems the only way to measure
forward traveling waves "along the antenna" is to use a
traveling wave antenna like a terminated rhombic.
--
73, Cecil, IEEE, OOTC, *http://www.w5dxp.com

I think that is pretty accurate Cecil.
Richard took to argueing with Dr Davis working at MIT
where he argued that the Laws of Maxwell do not equate mathematically
to the laws of other masters.He was speaking in his normal Olde
English term which is talking instead of communicating until he drove
the good Doctor away in fraustration.
Richard took that as a victory for Shakesphere over the degree in
mathematics that
Dr Davis earned. Richard now believes he has advanced in the pecking
order in matters relating to Radio no less.

wrote:
Jim's most recent posting is a good example. We were talking about
measuring current along a dipole. I assumed that would mean measuring
the standing-wave current, but Jim introduced the notion of measuring
travelling wave currents. When challenged as to how we might do that,
we got a URL pointing us to a simple standing wave meter - it
certainly can't discriminate Forward and Reverse.

I just happen to have the answer for anyone with EZNEC. The
following EZ files have been modified to run with the free
demo version of EZNEC.

The following inverted-V antenna is a standing-wave antenna.

http://www.w5dxp.com/inv_v.EZ

The segment currents in one half of the inverted-v look
like this:

EZNEC+ ver. 4.0
actual dipole 5/1/2009 5:12:15 PM
--------------- CURRENT DATA ---------------
Frequency = 3.644 MHz
Wire No. 2:
Segment Conn Magnitude (A.) Phase (Deg.)
1 W1E2 1 0.00
2 .97807 -0.33
3 .93414 -0.65
4 .86875 -0.94
5 .78291 -1.21
6 .67796 -1.46
7 .55552 -1.70
8 .41724 -1.94
9 .26438 -2.17
10 Open .09505 -2.40


The following inverted-V antenna is a traveling-wave antenna.

http://www.w5dxp.com/inv_vT.EZ

The segment currents in one half of the terminated inverted-v
look like this:

EZNEC+ ver. 4.0
actual dipole 5/1/2009 5:22:42 PM
--------------- CURRENT DATA ---------------
Frequency = 3.644 MHz
Wire No. 2:
Segment Conn Magnitude (A.) Phase (Deg.)
1 W1E2 1 0.00
2 .99572 -8.77
3 .99064 -18.12
4 .9799 -27.18
5 .96293 -36.30
6 .94055 -45.74
7 .91497 -55.78
8 .8899 -66.70
9 W3E1 .87103 -79.05

Wire No. 3:
Segment Conn Magnitude (A.) Phase (Deg.)
1 W2E2 .86769 -87.01


The two antennas are identical except one is terminated in
its characteristic impedance and one is not. This is the
best way I know of to illustrate the difference between
the currents on a standing-wave antenna and the currents
on a traveling-wave antenna.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

wrote:
Jim & Richard,

I guess I'll retire gracefully because I'm not privy to the "history"
between individuals on this Forum and I'm now not even sure when
answers are to be taken seriously or as a joke.

Jim's most recent posting is a good example. We were talking about
measuring current along a dipole. I assumed that would mean measuring
the standing-wave current, but Jim introduced the notion of measuring
travelling wave currents.

A point of correction here. I believe you will find the notion detailed
on Cecil's web page.

When challenged as to how we might do that,
we got a URL pointing us to a simple standing wave meter - it
certainly can't discriminate Forward and Reverse.

Please let me apologize for my error about the nature of the article.
You are correct. The 'calibration fixture' featured in the 2nd
photograph is directional. An examination of its inner workings would of
course reveal circuits which measure currents and voltages in traveling
waves. It is to circuits such as those that I have referred.

From other postings I've read I take Jim to be a pretty knowledgeable
guy - so this has to be a wind-up, right?

He's a guy with a limited amount of time and patience honestly
attempting to subvert the ridiculous by stating the obvious. Most
everyone here has already given up trying. Good luck to you, should you
decide to try it.

ac6xg

On Fri, 1 May 2009 14:44:10 -0700 (PDT), wrote:

Jim & Richard,

I guess I'll retire gracefully because I'm not privy to the "history"
between individuals on this Forum and I'm now not even sure when
answers are to be taken seriously or as a joke.

Hi Steve,

You have now noted the greater contribution of comedy that inhabits
these discussions. Unfortunately, and as you indicate, those thin
jokes are rather in-bred.

Jim's most recent posting is a good example. We were talking about
measuring current along a dipole. I assumed that would mean measuring
the standing-wave current, but Jim introduced the notion of measuring
travelling wave currents.

Ah! The history you are unaware of (and it hides in the terms of
invention that populate the theories being assembled behind the
curtain) is that BOTH currents are under consideration. Unfortunately,
and you have the capacity to appreciate this, some characteristics of
one are migrating into the conversation of the other. Hence, we
return to the keyword: phase.

In one realm, phase is pointless, in the other, it has significance.
As the term phase migrates between the two, both realms' discussion
are polluted.

When challenged as to how we might do that,
we got a URL pointing us to a simple standing wave meter -

Not really. It is a simple current meter - the page literally shouts
that out.

it
certainly can't discriminate Forward and Reverse.

That is correct, but I mentioned such discrimination is possible from
the Bruene SWR bridge. As I wrote previously, no one measures forward
and reverse currents on antenna elements. Construction examples would
be rare.

With care and practice as offered at the link, which attends the
issues of error (largely dismissed from the greater consideration of
"measurement" proofs offered), the Bruene style could similarly be
achieved. It is neither a difficult concept, nor a technical hurdle.

From other postings I've read I take Jim to be a pretty knowledgeable
guy - so this has to be a wind-up, right?

Give it another thousand postings sprinkled over the decade to do
that. We have barely given up on fractal antennas.

73's
Richard Clark, KB7QHC

Jim Kelley wrote:
wrote:
Jim's most recent posting is a good example. We were talking about
measuring current along a dipole. I assumed that would mean measuring
the standing-wave current, but Jim introduced the notion of measuring
travelling wave currents.

A point of correction here. I believe you will find the notion detailed
on Cecil's web page.

Yes, the total measured current on a standing wave antenna
is primarily standing wave current. The total measured current
on a traveling wave antenna is primarily traveling wave
current. Please see my last posting.

He's a guy with a limited amount of time and patience honestly
attempting to subvert the ridiculous by stating the obvious.

Obviously, a 100 turn, 10 tpi, 2" dia 75m loading coil cannot
have the 3 nS delay that W8JI "measured". Do you disagree?
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

On Fri, 01 May 2009 15:47:41 -0700, Richard Clark
wrote:

When challenged as to how we might do that,
we got a URL pointing us to a simple standing wave meter -

Not really. It is a simple current meter - the page literally shouts
that out.

it
certainly can't discriminate Forward and Reverse.

That is correct, but I mentioned such discrimination is possible from
the Bruene SWR bridge. As I wrote previously, no one measures forward
and reverse currents on antenna elements. Construction examples would
be rare.

With care and practice as offered at the link, which attends the
issues of error (largely dismissed from the greater consideration of
"measurement" proofs offered), the Bruene style could similarly be
achieved. It is neither a difficult concept, nor a technical hurdle.

Hi Steve,

I hope you are still following the thread, because as bad as the
theory gets, there is always room for instruction - just not in phase.

I will expand on my comment of both the meter pointed to, its
construction practices, and the topic of accuracy (something everyone
offers, but can never prove).

First, as to its standing wave meter capacity (in terms of
conventional SWR meter usage). The last word, capacity, arises in
Tom's (W8JI's linked to) page:
The lack of large metallic components minimizes stray capacitance
and
I did not add a Faraday shield because the shield would increase the capacitance
I am now leveraging the word capacity to mean ability in contrast to
Tom's literal engineering application - and yet there is something to
be said about such a meter having the "capacity" to measure forward or
reverse products (as would a conventional SWR meter).

Capacitance is required to give the meter the capacity (ability) to
measure these currents. The Bruene SWR bridge has one side that is
driven by an inductive coupling, and the other side driven by a
capactive coupling. Through the combination of the two, the PHASES
contribute to either a reverse or forward energy product
(conventionally expressed as power). Clearly the link at Tom's page
illustrates half of the Bruene SWR bridge, and if that Faraday shield
had been tapped (instead of discarded), the meter could have revealed
the separate currents.

But nobody is interested - it offers nothing new. You will find 0 to
no construction examples of this more than rare application. Futher,
given its absence of discussion here in all these years, no one is
actually interested in "measuring" what they have proven through their
measurements.... Sorry Steve, another in-bred joke.

Moving beyond the hillarity that ensues from these obvious shortfalls
of academic navel gazing; there is still the accuracy to consider.

On the face of what is offered at Tom's page, there is an immediate
and irrevocable error of 5% built into the instrument as described
sitting in its calibration fixture. Under other circumstances, that
error could easily eclipse 100%. Suffice it to say it will never
achieve better without a small book of charts.

As I offered, accuracy is often claimed, but rarely (never) proven.

This is a simple counter-proof. Tom expresses it without being aware
of the implications:
T1 is a current transformer. ...
When the single turn primary (a whip or mast) has 1 ampere,
the secondary will have .05 amperes (inverse of the turns ratio).
all very standard stuff as you may well note. Going on:
This type of meter is much more reliable and linear
than thermocouple RF ammeters, and perturbs systems much less.
This, of course, is related to the "stated but not proven" class of
statements that litter the WWW (much less this thread).

Here is the literal error:
I've applied 50 watts to a precision 50 ohm load,
making wire current 1-ampere.

Let's assemble these statements. We have a current transformer. It
is loaded with 100 Ohms with a lightly coupled linear indicator. It
has 50 Watts applied through it to a load. That load is 50 Ohms.

What the meter should indicate is a current of 0.9535A if we are to
believe that the 50W is absolutely accurate (it is not, but we will
skip that for another discussion). The author, Tom, offers to trim
the potentiometer for a 1.000A reading - WRONG!

How can this be? It is all in the statements offered above. The
current transformer is also a RESISTANCE TRANSFORMER. That 100 Ohm
load to its secondary is cast into the primary as an in-series 5 Ohm
resistor adding to the 50 Ohm nominal load. The instrument is
injecting itself into the measurement and this presents the statement:
perturbs systems much less.
in a new light as it is quite easily demonstrated exactly how much (if
we ignore other sources of error) this construction example will
perturb the system and nothing is said in comparison to the technology
being replaced (thermocouples). Such is poor reporting.

What becomes of that error in a short monopole whose radiation
resistance is equal to that 5 Ohm insertion loss?
FS accuracy is not required in comparison measurements,
True enough, but it then ignores what I've offered above:
since the meter references against itself.
a 5 Ohm instrument load in series with a 5 Ohm radiator (irrespective
of phase contributions due to size) will seriously change the fabric
of the system. Such is the compounding of poor reporting.

If one were to claim to have made ANY current measurements, and then
wholly ignore the contribution of errors, then the discussion of phase
in a system such as a 5 Ohm radiator with a 5 Ohm instrument loss is
going to be absurd. Such are the fruits of poor reporting.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
. . .
On the face of what is offered at Tom's page, there is an immediate
and irrevocable error of 5% built into the instrument as described
sitting in its calibration fixture. Under other circumstances, that
error could easily eclipse 100%. Suffice it to say it will never
achieve better without a small book of charts.

As I offered, accuracy is often claimed, but rarely (never) proven.

This is a simple counter-proof. Tom expresses it without being aware
of the implications:
T1 is a current transformer. ...
When the single turn primary (a whip or mast) has 1 ampere,
the secondary will have .05 amperes (inverse of the turns ratio).

This means the turns ratio is 1:20.

all very standard stuff as you may well note. Going on:
This type of meter is much more reliable and linear
than thermocouple RF ammeters, and perturbs systems much less.
This, of course, is related to the "stated but not proven" class of
statements that litter the WWW (much less this thread).

Here is the literal error:
I've applied 50 watts to a precision 50 ohm load,
making wire current 1-ampere.

Let's assemble these statements. We have a current transformer. It
is loaded with 100 Ohms with a lightly coupled linear indicator. It
has 50 Watts applied through it to a load. That load is 50 Ohms.

What the meter should indicate is a current of 0.9535A if we are to
believe that the 50W is absolutely accurate (it is not, but we will
skip that for another discussion). The author, Tom, offers to trim
the potentiometer for a 1.000A reading - WRONG!

How can this be? It is all in the statements offered above. The
current transformer is also a RESISTANCE TRANSFORMER. That 100 Ohm
load to its secondary is cast into the primary as an in-series 5 Ohm
resistor adding to the 50 Ohm nominal load.

The resistance is transformed in the ratio of N^2:1, which is 400:1 for
a 20:1 turns ratio. So the insertion resistance is 100/400 = 0.25 ohm,
not 5. I'm confident it works as Tom claims.

. . .

If one were to claim to have made ANY current measurements, and then
wholly ignore the contribution of errors, then the discussion of phase
in a system such as a 5 Ohm radiator with a 5 Ohm instrument loss is
going to be absurd. Such are the fruits of poor reporting.

No, this is the fruit of poor reporting.

Roy Lewallen, W7EL

On Fri, 01 May 2009 18:00:40 -0700, Roy Lewallen
wrote:

The resistance is transformed in the ratio of N^2:1, which is 400:1 for
a 20:1 turns ratio. So the insertion resistance is 100/400 = 0.25 ohm,

Hi Roy,

Yes, quite so.

not 5. I'm confident it works as Tom claims.

It works as it claims is obvious, but not for SWR (neither claimed,
nor something you show interest in) - not that it should, but could.
We aren't going there either (few would as such an application has no
obvious merit). Pursuing the topic of reported phase does not appear
to be productive. A curiousity all around.

If one were to claim to have made ANY current measurements, and then
wholly ignore the contribution of errors, then the discussion of phase
in a system such as a 5 Ohm radiator with a 5 Ohm instrument loss is
going to be absurd. Such are the fruits of poor reporting.

No, this is the fruit of poor reporting.

No, that you caught me in a detail with that detail mishandled by me.
Complements! The detail was quite accurate; so much so that you
accepted it (it was also sourced by Tom) in your reply. That is the
value of good reporting. The net result is a very short transaction
of point-counter point that doesn't demand 300 posts of careful
parsing. My fault was poor application, certainly. You probably
stole Art and Cecil's delight at catching me there. ;-0

73's
Richard Clark, KB7QHC