Current through coils
 

John Popelish wrote:
I don't think so. Your claim is that one can use a resonant condition
to find the current delay at that frequency, and then, assume that that
delay holds for all other, lower frequencies.

At other *HF* frequencies and within reason, John, within reason.
A two to one range wouldn't surprise me. Tom's five to one range
from 16 MHz to 4 MHz is surprising. If the frequency kept going
to 1 MHz, would the delay go below 3 nS? If Tom measured the delay
at the self-resonant frequency of 16 MHz, would he measure 16 nS?
If one plots the delay from 1 MHz to 16 MHz would there be any
nonlinear points on the curve as implied by Tom's measurements?

I am skeptical that this
is the case for any device that is not inherently a constant delay
device.

I didn't mean to imply that it was an absolutely constant
delay device. If it is well designed and if the environment
is held constant, it should exhibit approximately the same
delay over HF below its self-resonant frequency. Tom's
measurements implied a 5 to 1 range shift in delay from a
4 to 1 range shift in frequency. Delays changing faster than
the frequency certainly don't make sense to me. What would
be the cause?

From 16 Mhz to 4 Mhz:
Does L vary much with frequency? Why?
Does C vary much with frequency? Why?
Does R vary much with frequency? Why?
Does G vary much with frequency? Why?
These are the parameters in the "phase constant" equation.

Let's take a look at my measured data where I changed the
stinger by 2 feet from zero to 12 feet. The 75m bugcatcher
coil is mounted on a mobile antenna mount on my GMC pickup.
For clearence purposes, it has a one foot bottom section.

The stinger goes from 0' to 12': 0, 2, 4, 6, 8, 10, 12
The resonant frequency goes from: 6.7, 5.1, 4.3, 3.8, 3.5, 3.2, 3.0 MHz
I just don't see any nonlinear changes such as Tom reported.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Addressed to nobody in particular.

From basic transmission line theory, the velocity of propagation along
a coil is estimated by -

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.

The velocity factor = V / c and Zo = Sqr( L / C ).

Attenuation (loss) = R / 2 / Zo nepers, where R is wire resistance
plus radiation resistance.

From which other interesting facts can be deduced.
----
Reg.

Current through coils
 

John Popelish wrote:
... I see no reason to assume the transmission line method
(delay independent of frequency) strictly applies. It might, but it
would take more than you saying so to assure me that it is a fact.

Assume the environment of the coil is fixed like the variable
stinger measurement I reported earlier. Besides the frequency
term, the phase constant depends upon L, C, R, and G as does
the Z0 equation. Why would the L, C, R, and G change appreciably
over a relatively narrow frequency range as in my bugcatcher coil
measurements going from 6.7 MHz to 3.0 MHz?

And I didn't mean to imply that the delay is "independent" of
frequency, just that it is not nearly as frequency dependent
as Tom's measurements would suggest. If Tom made his measurements
from 1 MHz to 16 MHz, what do you think the curve would look like?

Freq 1 2 4 8 16 MHz
Delay ___ ___ 3 ___ 16 nS

That looks non-linear to me. How about you?
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Roy Lewallen wrote:
It's my policy to keep all email confidential.

Apparently not. That was a private email. Publishing it
in public without my permission is unethical but seems you
and Tom will seemingly stop at nothing to keep promoting
your myths.

You have, over and over, rejected the distributed network
model even though you know it is a superset of the lumped-
circuit model. Would you agree with me that after all this
time, you cannot possibly plead ignorance?
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

David G. Nagel wrote:
The fiber optic leads are used in the experiment mentioned in the story
linked by the URL that was recently mentioned in this thread. I think
the whole thing is hilarious and was especially struck by the use of
glass fiber to measure an electrical/magnet phenominum with no
indication how the measurement is made. Sort of in line with someone's
line of thinking in this thread.

There exist transducers that will convert RF to light on one end of
a fiber optics cable and back to RF at the other end. It's no big
deal and keeps the transfer of information from being affected by
EM fields.
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Oops!

Zo = Sqrt( L / C)

Current through coils
 

Reg Edwards wrote:
From basic transmission line theory, the velocity of propagation along
a coil is estimated by -

V = 1 / Sqrt( L * C ) metres per second,

So Reg, for a fixed installation, why would L and C change
much with frequency, like from 16 nS at 16 MHz to 3 nS at
4 MHz? If we took it down to 1 MHz, would the delay go
below 3 nS?
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

Roy Lewallen wrote:
I believe it's relevant to the discussion at
hand on this group, so I'll share it here, ...

So you believe my personal feelings about you are relevant
to a technical discussion???? Exactly which technical
parameters are affected by my feelings about you?

Every time this subject comes up, more and more people
realize that the r.r.a.a gurus are not omniscient.

Here's a smattering of the email I've received over
the past week. Unlike you, I won't mention any names.

"I hope ... that [X and Y] will acknowledge the validity
of your approach." [X and Y are posters to r.r.a.a]

"You are moving pretty fast, but nothing that you are saying
sounds like there are any glaring errors."

"Distributed constants not lumped constants prevail."

"I, too, am skeptical of that 3 ns delay."

" ...your Corum reference certainly ends the debate."

"I want to let you know your dedication to principle and rational
analysis ... are inspiring to many of us."

"The unwillingness of the "gurus" to answer specific technical
questions is pretty disappointing."

Roy, are you listening to that last comment?
--
73, Cecil http://www.qsl.net/w5dxp

Current through coils
 

"Cecil Moore" wrote in message
. ..
Reg Edwards wrote:
From basic transmission line theory, the velocity of propagation
along
a coil is estimated by -

V = 1 / Sqrt( L * C ) metres per second,

So Reg, for a fixed installation, why would L and C change
much with frequency, like from 16 nS at 16 MHz to 3 nS at
4 MHz? If we took it down to 1 MHz, would the delay go
below 3 nS?
--
73, Cecil http://www.qsl.net/w5dxp

==========================================

Sorry Cec, I havn't the foggiest idea.

Having started it, I havn't been taking much notice of this
long-winded thread. Its all too clever for poor little me! ;o)
----
Reg.

Current through coils
 

Roy Lewallen wrote:
John Popelish wrote:
I wish I could, but this is the first I have heard of such
instrumentation. That is why I would like to read more about it.

Hopefully the poster mentioning the optical probe will explain a bit
more. But I recall seeing optically coupled instrumentation used in an
EMI screen room to couple signals in and out. To my knowledge, though,
the probes themselves were conventional, and fiber optics were used
only to replace connecting wires.

Such probes are routinely used for RFI, RF hazards and screened-room
measurements, where connecting wires would disturb the fields or act as
pathways for RF leakage.

They do have a disadvantage that might be relevant to this discussion:
because the probe head has to be self-powered, and has to include some
kind of encoder and optical transmitter as well as the normal current
transformer, the battery and extra area of PC board will increase the
probe's self-capacitance.

A different kind of fibre-optic probe is used in basic research on RF
hazards, to measure very localized and very small temperature changes in
simulated human heads and bodies. These microprobes are purely optical,
and are sensing some temperature-dependent optical property of liquid
crystals(?) at the probe tip.


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek