Cecil Moore wrote:

Jim Kelley wrote:

Cecil Moore wrote:

Z0 didn't change. The load didn't change. Therefore, the
SWR didn't change. What exactly do you think changed?


I think the circuit changed. Don't you?


The circuit changed without changing the forward power,
reflected power, and SWR so nothing of interest to the
present topic (V/I ratio) changed.

Do you know what dictates the SWR in a distributed network?
Certainly not the length of the feedline or the removal
of a tuner (assuming lossless conditions).

Well, it's certainly true that both circuits are missing the 50 ohm
impedance discontinuity in the middle, which is at least one of the
"present topics" (and my point).

I'll just go ahead and say what you really want me to say:

You're good enough, you're smart enough, and doggone it, people like you!

:-)

ac6xg

Dave wrote:
i'm not agreeing with how you assume the 50 ohm impedance of the meter out
of the circuit.

I don't think you understand what I was saying. It takes a
certain length of feedline to establish a Z0 environment
for the forward and reverse traveling TEM waves, i.e. to
force Vfor/Ifor = Vref/Iref = Z0.

and i am not agreeing that there should be reflected power
measured by the meter in the case of the 50 ohm load on the end of a 1/2
wave 75 ohm line.

I never said it "should" measure that reflected power. What I
said is if it doesn't measure the reflected power that exists,
it is not giving a valid measurement of reflected power. A properly
calibrated meter will indeed measure the reflected power that exists.
--
73, Cecil http://www.qsl.net/w5dxp

Richard Clark wrote:
Any error of misunderstanding Owen's post is entirely your own.

Thanks, Richard, that really helps a lot.
--
73, Cecil http://www.qsl.net/w5dxp

"Cecil Moore" wrote in message
.. .

The actual SWR on a lossless line doesn't change. Yet, in another
posting, I showed that moving the Bird 1/4WL closer to the load
caused a reported SWR change by the Bird from 1:1 to 2.25:1. How
could both results possibly be right?
--
73, Cecil http://www.qsl.net/w5dxp

The Bird does not know squat about transmission lines, foreward, or
reflected. It only cares about impedance. If you connect a 50 Ohm load to it
through 1/4 wave of 75 Ohm coax, the impedance the Bird sees will be
transformed to 112.5 Ohms; hence the 2.25 SWR. (Actually, a 2.25:1 impedance
ratio)

I have a computer simulation of that type of meter, which lets me do things
you can not do in the real world, for instance having a 50 KW source on each
side of the meter. It can separate out the signals in the two directions of
transmission, but only when it is terminated in 50 Ohms, when there are no
reflections.

Tam/WB2TT

Jim Kelley wrote:
Well, it's certainly true that both circuits are missing the 50 ohm
impedance discontinuity in the middle, which is at least one of the
"present topics" (and my point).

Jim, if the ratio of net voltage to net current is already 50 ohms,
then your Bird "impedance discontinuity" should cause that to change
but there is no evidence whatsoever that it changes anything. Conclusion:
The insertion of the Bird does not appreciably change the V/I ratio.
--
73, Cecil http://www.qsl.net/w5dxp

Owen Duffy wrote:
I fully expected someone to object, not only to object, but to do so
without any original experimental evidence ...

Owen, there was absolutely no reason for anyone else to do any
additional experiments. Your own experiment proved that the Bird
wattmeter was ignoring the 4.1667 watts of reflected energy flowing
through it when installed in the 75 ohm environment. You proved
exactly the opposite of what you were trying to prove.
--
73, Cecil http://www.qsl.net/w5dxp

Tam/WB2TT wrote:

"Cecil Moore" wrote:
The actual SWR on a lossless line doesn't change. Yet, in another
posting, I showed that moving the Bird 1/4WL closer to the load
caused a reported SWR change by the Bird from 1:1 to 2.25:1. How
could both results possibly be right?

The Bird does not know squat about transmission lines, foreward, or
reflected. It only cares about impedance. If you connect a 50 Ohm load to it
through 1/4 wave of 75 Ohm coax, the impedance the Bird sees will be
transformed to 112.5 Ohms; hence the 2.25 SWR. (Actually, a 2.25:1 impedance
ratio)

Yes, that's exactly what I said in the other posting. But some
people seem to believe that inserting a Bird into a transmission
line with a Z0 other than 50 ohms magically changes it to a 50
ohm environment. The 40mm of transmission line inside the Bird
is supposed to accomplish that miracle.
--
73, Cecil http://www.qsl.net/w5dxp

On Fri, 14 Oct 2005 00:24:09 GMT, Cecil Moore wrote:
Your own experiment proved that the Bird wattmeter was ignoring
the 4.1667 watts of reflected energy flowing through it
This fiction is entirely your own invention and trying to put Owen's
frame around your cartoon does not elevate this nonsense to art.

You have done nothing to offer any substance to your claim except the
time worn tradition of repetition, deflection, and ignoring the
observables by insisting error exists where it is not.

What reflections exist, exist at the input port of the Bird which is
50 Ohms by design, and which is attached to a 50 Ohm load by
deliberate selection. The Bird's response confirms the load, and the
rest stands on 50 years of Bird quality construction (he's not using
the poorer model with PL-259s).

Owen's work stands on its own, despite your chatter of a nabob of
negativity (apologies to our ex-VP-ex-convict of the GOP).

Richard Clark wrote:

On Fri, 14 Oct 2005 00:24:09 GMT, Cecil Moore wrote:

Your own experiment proved that the Bird wattmeter was ignoring
the 4.1667 watts of reflected energy flowing through it

This fiction is entirely your own invention ...

Sorry, I am just quoting Owen's results. There was 4.1667 watts
of reflected energy flowing back through the Bird. The Bird
indicated zero watts. That's an infinite percentage error on
reflected power for the Bird and proves my point that a 50 ohm
wattmeter used in a 75 ohm environment is like using a hammer
on a screw. To paraphrase: when the only tool one has is a 50
ohm Bird, every Z0 environment looks like 50 ohms.
--
73, Cecil http://www.qsl.net/w5dxp

Richard Clark wrote:
What reflections exist, exist at the input port of the Bird which is
50 Ohms by design, and which is attached to a 50 Ohm load by
deliberate selection.

But the 50 ohm load is attached through a piece of 75 ohm coax
supporting an SWR of 1.5:1. If you don't realize that fact, I
feel sorry for you.
--
73, Cecil http://www.qsl.net/w5dxp

On Fri, 14 Oct 2005 00:51:02 GMT, Cecil Moore wrote:

Sorry, I am just quoting Owen's results.
There is nothing in his entire scope of postings that presents:
There was 4.1667 watts of reflected energy flowing back through the Bird.
Which is absurd.

This is simply more of the same attempt of your trying to cram a
trade-unionist pamphlet into the frame built by Owen. It is not only
the wrong topic, it doesn't even fit.

Owen has demonstrated quite clearly that your assertion
It takes a certain length of feedline to establish a Z0 environment
is blarney from one end of your feedline to the other. Another way of
saying mythbusted, or if you have grandkids, they would say
you've been served!

On Fri, 14 Oct 2005 00:53:03 GMT, Cecil Moore wrote:
I feel sorry for you.
You and Mother Theresa - did the Cardinals miss electing you too?
Don't fret, maybe there's work available as Vatican Bat Boy.

"Owen Duffy" wrote
Entirely OT:

Reg, you are way to impatient. There are very few Australian Shiraz
that should be taken in less than three years.
======================================
I'm 80 next month.
======================================

I can't recall the "instructions" on the back of the bottle that
tell
one what to drink it with and when to drink it, but Banrock Station
produce "everday drinking" quality reds that should stand a few
years
cellaring,

==========================================
The bottle was chosen at random by my daughter from the supermarket
shelf. Following your message I retrieved it from the trash bin.

The label did not mention a 'drink by' date. But it does mention eat
with a mature blue cheese which is a firm favorite of mine. I've long
given up worrying about cholesterol.
====================================

IIRC, the labels carry a bit of a story on their wildlife refuge, do
they get to tell you what to eat with it?

====================================
Yes. I looked up Banrock Station's website about their contributions,
internationally, towards preservation of wetlands, nature reserves,
and the many forms of wildlife therein. There's even a photograph of
a water snail. Very interesting.

I guess you are far more knowledgeable about wines than I am. Thanks
for drawing my attention to the bottle.
----
Reg, G4FGQ

On Fri, 14 Oct 2005 01:44:02 +0000 (UTC), "Reg Edwards"
wrote:


I guess you are far more knowledgeable about wines than I am. Thanks
for drawing my attention to the bottle.

Not at all to both.

But, I do enjoy a glass of red... unfortunately my feet are getting
less happy about that.

Owen
--

"Cecil Moore" wrote
The insertion of the Bird does not appreciably change the V/I ratio.

====================================
Cec,

I have tried to avoid entering this argument.

But it appears to me that ALL SWR meters work on the principle of a
common, identical, take off point for both voltage and current
samples.

Therefore, anything inside the meter which could constitute a
transmission line, no matter how long or short, if it separates the
two effective take-off points, it is a small source of error and its
actual length otherwise plays no part in the measuring process.

( I mean its actual length is not included in the basic design
calculations, except perhaps in rare instances to minimise the error.)

( The error arises from a phase-shift error in tapping off the current
sample. There may be no problem with defining the location of the
voltage sample. All depends on meter construction and the tapping
methods which vary but do not affect the basic design principle of a
common tapping point.)

I am not trolling. Please read very carefully. Try to limit yourself
to HF and VHF. Do you agree? Yes or No?
----
Reg, G4FGQ.

On Fri, 14 Oct 2005 01:55:28 GMT, Owen Duffy wrote:

But, I do enjoy a glass of red... unfortunately my feet are getting
less happy about that.

Hi Owen,

Gout?

73's
Richard Clark, KB7QHC

On Thu, 13 Oct 2005 22:37:43 -0700, Richard Clark
wrote:


Gout?

Of course.

Owen
--

Gee! I was born with gout! My parents were not drinkers. My doctor says
it is genetic.

I did not know that red wine caused gout! :-)

Actually, it spikes uric acid. Gout is the inability of my kidneys to
eliminate the uric acid as waste.

Richard Clark wrote:
On Fri, 14 Oct 2005 01:55:28 GMT, Owen Duffy wrote:


But, I do enjoy a glass of red... unfortunately my feet are getting
less happy about that.


Hi Owen,

Gout?

73's
Richard Clark, KB7QHC

"Cecil Moore" wrote in message
om...
Dave wrote:
i'm not agreeing with how you assume the 50 ohm impedance of the meter
out of the circuit.

I don't think you understand what I was saying. It takes a
certain length of feedline to establish a Z0 environment
for the forward and reverse traveling TEM waves, i.e. to
force Vfor/Ifor = Vref/Iref = Z0.

and what the experiment pointed out was that the length of feedline attached
is immaterial, the 50ohm environment is established within the meter itself
and it doesn't care what the length of feedline attached is.

"Cecil Moore" wrote in message
. com...
Tam/WB2TT wrote:

"Cecil Moore" wrote:
The actual SWR on a lossless line doesn't change. Yet, in another
posting, I showed that moving the Bird 1/4WL closer to the load
caused a reported SWR change by the Bird from 1:1 to 2.25:1. How
could both results possibly be right?

The Bird does not know squat about transmission lines, foreward, or
reflected. It only cares about impedance. If you connect a 50 Ohm load to
it through 1/4 wave of 75 Ohm coax, the impedance the Bird sees will be
transformed to 112.5 Ohms; hence the 2.25 SWR. (Actually, a 2.25:1
impedance ratio)

Yes, that's exactly what I said in the other posting. But some
people seem to believe that inserting a Bird into a transmission
line with a Z0 other than 50 ohms magically changes it to a 50
ohm environment. The 40mm of transmission line inside the Bird
is supposed to accomplish that miracle.

yep, that is true, and that is what the experiment shows. the 50 ohm load,
even though it is caused by a 75 ohm line, is far enough away from the
sensor that it sees it as 50 ohms. so the 'miracle' length is obviously
less than 40mm.

"Cecil Moore" wrote in message
. com...
Owen Duffy wrote:
I fully expected someone to object, not only to object, but to do so
without any original experimental evidence ...

Owen, there was absolutely no reason for anyone else to do any
additional experiments. Your own experiment proved that the Bird
wattmeter was ignoring the 4.1667 watts of reflected energy flowing
through it when installed in the 75 ohm environment. You proved
exactly the opposite of what you were trying to prove.

ah, but the sensor isn't in a 75 ohm environment, it is in a 50 ohm
environment inside the meter and sees a 50 ohm load.

I did not know that red wine caused gout! :-)

It's port wine and pheasant which causes gout.

Richard Clark wrote:
On Fri, 14 Oct 2005 00:51:02 GMT, Cecil Moore wrote:


Sorry, I am just quoting Owen's results.

There is nothing in his entire scope of postings that presents:

There was 4.1667 watts of reflected energy flowing back through the Bird.

Which is absurd.

The SWR on the 75 ohm line is 1.5:1. If 100 watts is delivered to
the load, there's 4.1667 watts of energy reflected from the load
and flowing back through the Bird. The Bird doesn't see it because
the Bird is calibrated for the wrong Z0.

Owen has demonstrated quite clearly that your assertion

It takes a certain length of feedline to establish a Z0 environment

is blarney from one end of your feedline to the other.

Really? They why bother with characteristic impedance at all?
If Z0 doesn't establish a Z0 environment, then all transmission
lines are just alike and transmission theory is hogwash.
--
73, Cecil http://www.qsl.net/w5dxp

Reg Edwards wrote:
But it appears to me that ALL SWR meters work on the principle of a
common, identical, take off point for both voltage and current
samples.

There are a number of different designs. One very popular class of
designs samples the voltage and current essentially at a point. If
the device is in a 50 ohm environment and the two samples are equal
in magnitude and phase, there is no reflected power. If the device
is in a non-50 ohm environment and the two samples are equal in
magnitude and phase, reflected power exists at the sample point even
though the device reports none.

Therefore, anything inside the meter which could constitute a
transmission line, no matter how long or short, if it separates the
two effective take-off points, it is a small source of error and its
actual length otherwise plays no part in the measuring process.

( I mean its actual length is not included in the basic design
calculations, except perhaps in rare instances to minimise the error.)

( The error arises from a phase-shift error in tapping off the current
sample. There may be no problem with defining the location of the
voltage sample. All depends on meter construction and the tapping
methods which vary but do not affect the basic design principle of a
common tapping point.)

I am not trolling. Please read very carefully. Try to limit yourself
to HF and VHF. Do you agree? Yes or No?

All of the above is why this class of wattmeters, including the Bird,
does not establish a 50 ohm environment merely by being inserted in
a non-50 ohm system. The Bird samples voltage and current essentially
at a point, assumes it is in a 50 ohm environment, and reports the
power reading. If it is not in a 50 ohm environment, the power reading
that it reports will be wrong as Owen's experiment proved.
--
73, Cecil http://www.qsl.net/w5dxp

Dave wrote:

"Cecil Moore" wrote:
I don't think you understand what I was saying. It takes a
certain length of feedline to establish a Z0 environment
for the forward and reverse traveling TEM waves, i.e. to
force Vfor/Ifor = Vref/Iref = Z0.

and what the experiment pointed out was that the length of feedline attached
is immaterial, the 50ohm environment is established within the meter itself
and it doesn't care what the length of feedline attached is.

The experiment proved that the 50 ohm environment is NOT established
because the Bird readings were wrong. The Bird reported 100 watts
forward power where the actual forward power was 104.1667 watts. The
Bird reported zero reflected power where the reflected power was
4.1667 watts. Thus the experiment proves my point. The Bird does not
yield accurate results when embedded in an environment other than
50 ohms.

All the Bird does is sample the voltage and current essentially at
a point. If the ratio of net voltage to net current happens to be
50 ohms, the Bird will report a matched condition, no matter what
the Z0 of the transmission line and no matter how much reflected
power actually exists at the measurement point. For instance:

XMTR--balun--1/2WL 450 ohm line--x--1/2WL 450 ohm line--50 ohm load

The SWR on the line is 9:1. The reflected power is 64% of the forward
power. If forward power equals 100 watts, reflected power will be
64 watts at point 'x'. Yet a Bird wattmeter inserted at point 'x'
will read zero reflected power. The environment is clearly 450 ohms.
The reflected energy doesn't tuck tail and run away when the Bird
is inserted. The Bird is simply giving the wrong reading for reflected
power because all it is looking at is voltage and current at a point.
This is such elementary transmission line stuff that I cannot believe
there is any argument about it.

The insertion of a Bird wattmeter in the middle of a non-50 ohm
environment does NOT eliminate the reflected energy that exists
before the insertion.
--
73, Cecil http://www.qsl.net/w5dxp

Dave wrote:

"Cecil Moore" wrote:
Yes, that's exactly what I said in the other posting. But some
people seem to believe that inserting a Bird into a transmission
line with a Z0 other than 50 ohms magically changes it to a 50
ohm environment. The 40mm of transmission line inside the Bird
is supposed to accomplish that miracle.

yep, that is true, and that is what the experiment shows. the 50 ohm load,
even though it is caused by a 75 ohm line, is far enough away from the
sensor that it sees it as 50 ohms. so the 'miracle' length is obviously
less than 40mm.

So a one inch piece of 50 ohm coax forces the ratio of net voltage
to net current to be 50 ohms? Of course it does. You had me going
there for awhile. I didn't realize until now that you were pulling
my leg all the while.
--
73, Cecil http://www.qsl.net/w5dxp

Dave wrote:
ah, but the sensor isn't in a 75 ohm environment, it is in a 50 ohm
environment inside the meter and sees a 50 ohm load.

Again, 40mm is not enough to establish a 50 ohm environment
when embedded within a 75 ohm environment. The Bird is simply
sampling voltage and current without knowing the reference.
If the Bird were recalibrated for 75 ohms, it would read the
correct values in a 75 ohm environment.
--
73, Cecil http://www.qsl.net/w5dxp

"Cecil Moore" wrote in message
m...
Reg Edwards wrote:
But it appears to me that ALL SWR meters work on the principle of a
common, identical, take off point for both voltage and current
samples.

There are a number of different designs. One very popular class of
designs samples the voltage and current essentially at a point. If
the device is in a 50 ohm environment and the two samples are equal
in magnitude and phase, there is no reflected power. If the device
is in a non-50 ohm environment and the two samples are equal in
magnitude and phase, reflected power exists at the sample point even
though the device reports none.

Therefore, anything inside the meter which could constitute a
transmission line, no matter how long or short, if it separates the
two effective take-off points, it is a small source of error and its
actual length otherwise plays no part in the measuring process.

( I mean its actual length is not included in the basic design
calculations, except perhaps in rare instances to minimise the error.)

( The error arises from a phase-shift error in tapping off the current
sample. There may be no problem with defining the location of the
voltage sample. All depends on meter construction and the tapping
methods which vary but do not affect the basic design principle of a
common tapping point.)

I am not trolling. Please read very carefully. Try to limit yourself
to HF and VHF. Do you agree? Yes or No?

All of the above is why this class of wattmeters, including the Bird,
does not establish a 50 ohm environment merely by being inserted in
a non-50 ohm system. The Bird samples voltage and current essentially
at a point, assumes it is in a 50 ohm environment, and reports the
power reading. If it is not in a 50 ohm environment, the power reading
that it reports will be wrong as Owen's experiment proved.

ah, but if the bird does establish a 50 ohm 'environment' within its 40mm
housing then the reading that was actually obtained is indeed correct. so
now, how else could you read zero reflected power at that point if it didn't
establish that environment? what other evidence to you have that 40mm is
too short? if 40mm is too short then why do we worry at all about impedance
bumps in connectors that are 20mm or so long??? if 20mm is enough to see a
bump then that is obviously affecting the 'environment' on the line.

"Cecil Moore" wrote in message
m...
Dave wrote:

"Cecil Moore" wrote:
Yes, that's exactly what I said in the other posting. But some
people seem to believe that inserting a Bird into a transmission
line with a Z0 other than 50 ohms magically changes it to a 50
ohm environment. The 40mm of transmission line inside the Bird
is supposed to accomplish that miracle.

yep, that is true, and that is what the experiment shows. the 50 ohm
load, even though it is caused by a 75 ohm line, is far enough away from
the sensor that it sees it as 50 ohms. so the 'miracle' length is
obviously less than 40mm.

So a one inch piece of 50 ohm coax forces the ratio of net voltage
to net current to be 50 ohms? Of course it does. You had me going
there for awhile. I didn't realize until now that you were pulling
my leg all the while.
--

yep, sounds good to me. now, someone please put a bird meter on a tdr and
see what the characteristic impedance of it is internally. then put it on a
network analyzer and see if it does indeed transform the 'environment' from
75 to 50 ohms in its 40mm length. oh and while you are at it calculate the
s factors for all the transitions, those will come up in the discussion here
shortly.

Dave wrote:
ah, but if the bird does establish a 50 ohm 'environment' within its 40mm
housing then the reading that was actually obtained is indeed correct. so
now, how else could you read zero reflected power at that point if it didn't
establish that environment?

Would you like for me to go through the math of a voltage and
current sampled at a point without disturbing anything?

Assume the voltage is sampled such that 100v of net voltage
is sampled as 10 volts.

Assume the current is sampled such that two amps of net current
is sampled as 10 volts.

If these samples are in phase, adding them will result in 20v.
That equals 200 watts of forward power on the meter.

Subtracting them will result in zero volts. That equals zero
watts of reflected power on the meter.

The sampled net voltage and net current determine the 50 ohm
calibration. No 50 ohm environment required.

If the sample point is in 75 ohm coax with no reflections, the
sample voltage will be 12.3 volts and the sample current will
8.165 volts. Subtracting those sample values doesn't yield zero
so 41.35 watts of reflected power will be reported where none
actually exists.

So unless the mere writing of my words on this newsgroup
establishes a 50 ohm environment, the Bird doesn't need to
establish a 50 ohm environment to obtain the same above
results.

If the Bird indeed did control the environment into which
it was inserted, it would be violating a design goal for
measuring instruments and Bird wouldn't be selling many
of those highly intrusive devices. Bird wants the meter to
be as unobtrusive as possible and it is.
--
73, Cecil, http://www.qsl.net/w5dxp

Dave wrote:
now, someone please put a bird meter on a tdr and
see what the characteristic impedance of it is internally. then put it on a
network analyzer and see if it does indeed transform the 'environment' from
75 to 50 ohms in its 40mm length. oh and while you are at it calculate the
s factors for all the transitions, those will come up in the discussion here
shortly.

Probably all that is needed is to measure the Bird's s11
parameter while sitting in a 75 ohm environment. I'll
bet it's very close to zero.
--
73, Cecil, http://www.qsl.net/w5dxp

On Fri, 14 Oct 2005 12:55:57 GMT, Cecil Moore wrote:

They why bother with characteristic impedance at all?

This is your question and no one else's.

If Z0 doesn't establish a Z0 environment, then all transmission
lines are just alike and transmission theory is hogwash.

And this is your understanding - alone and in isolation from the rest
of us. Only you, by your logic arrived here by twists and turns.

It has no doubt slipped your mind that on one of those turns, the
requirement for x length of line was lost into the byways of this
labyrinth you traverse.

On Fri, 14 Oct 2005 14:45:34 GMT, Cecil Moore wrote:

bet it's very close to zero.
Another one of your rounding errors like where light 10 times brighter
than the sun is black.

"Cecil Moore" wrote in message
t...
Dave wrote:
ah, but if the bird does establish a 50 ohm 'environment' within its 40mm
housing then the reading that was actually obtained is indeed correct.
so now, how else could you read zero reflected power at that point if it
didn't establish that environment?

Would you like for me to go through the math of a voltage and
current sampled at a point without disturbing anything?

Assume the voltage is sampled such that 100v of net voltage
is sampled as 10 volts.

Assume the current is sampled such that two amps of net current
is sampled as 10 volts.

If these samples are in phase, adding them will result in 20v.
That equals 200 watts of forward power on the meter.

Subtracting them will result in zero volts. That equals zero
watts of reflected power on the meter.

The sampled net voltage and net current determine the 50 ohm
calibration. No 50 ohm environment required.

If the sample point is in 75 ohm coax with no reflections, the
sample voltage will be 12.3 volts and the sample current will
8.165 volts. Subtracting those sample values doesn't yield zero
so 41.35 watts of reflected power will be reported where none
actually exists.

but there will be a reflection at the 50 ohm to 75 ohm transition on the
load side of the meter.


So unless the mere writing of my words on this newsgroup
establishes a 50 ohm environment, the Bird doesn't need to
establish a 50 ohm environment to obtain the same above
results.

If the Bird indeed did control the environment into which
it was inserted, it would be violating a design goal for
measuring instruments and Bird wouldn't be selling many
of those highly intrusive devices. Bird wants the meter to
be as unobtrusive as possible and it is.

who says an instrument can't control it's environment? and who makes that a
design goal?? and who are you to say that bird wanted to make the meter
'unobtrusive'?? every instrument has some loading or effect on the circuit
it measures, some more than others. some even include 50 or 75 ohm loads
internally to load the circuit they are attached to. Ones that pass a
signal through their own sensing circuit often have more of an effect than
others.

Richard Clark wrote:
It has no doubt slipped your mind that on one of those turns, the
requirement for x length of line was lost into the byways of this
labyrinth you traverse.

Nope, it hasn't slipped my mind. So here's a question for you.
Is a zero length of 50 ohm coax sufficient to establish a
50 ohm environment?
--
73, Cecil, http://www.qsl.net/w5dxp

Richard Clark wrote:

Cecil Moore wrote:
bet it's very close to zero.

Another one of your rounding errors like where light 10 times brighter
than the sun is black.

I see you understand this subject just as well as you
understood that one.
--
73, Cecil, http://www.qsl.net/w5dxp

Dave wrote:
but there will be a reflection at the 50 ohm to 75 ohm transition on the
load side of the meter.

It was previously reported that the path through the Bird
is 40mm. The path through the Bird is actually about five
inches which is probably long enough to establish a 50 ohm
environment.
--
73, Cecil, http://www.qsl.net/w5dxp

"Cecil Moore" wrote in message
t...
Richard Clark wrote:
It has no doubt slipped your mind that on one of those turns, the
requirement for x length of line was lost into the byways of this
labyrinth you traverse.

Nope, it hasn't slipped my mind. So here's a question for you.
Is a zero length of 50 ohm coax sufficient to establish a
50 ohm environment?

you build it and i'll measure it and let you know.

Dave wrote:

"Cecil Moore" wrote:
Nope, it hasn't slipped my mind. So here's a question for you.
Is a zero length of 50 ohm coax sufficient to establish a
50 ohm environment?

you build it and i'll measure it and let you know.

It's in the middle of a piece of 75 ohm coax.
--
73, Cecil, http://www.qsl.net/w5dxp

"Cecil Moore" wrote in message
t...
Dave wrote:

"Cecil Moore" wrote:
Nope, it hasn't slipped my mind. So here's a question for you.
Is a zero length of 50 ohm coax sufficient to establish a
50 ohm environment?

you build it and i'll measure it and let you know.

It's in the middle of a piece of 75 ohm coax.

i just measured it at 50 ohms. so there.

create an impossible condition, get an impossible answer.