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?

You need to keep thinking about that. What if they are both right? Is
it really one continuous, uniform transmission line? Is SWR the same
everywhere in a tee stub circuit?

ac6xg

Jim Kelley 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?

You need to keep thinking about that. What if they are both right?

Here's the example sans the Bird. Between the tuner output
and the load, where exactly is the actual SWR = 1:1 and where
exactly is the actual SWR = 2.25:1? Answer: nowhere!

XMTR--tuner---1 WL 75 ohm coax---50 ohm load
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
Jim Kelley 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?


You need to keep thinking about that. What if they are both right?


Here's the example sans the Bird. Between the tuner output
and the load, where exactly is the actual SWR = 1:1 and where
exactly is the actual SWR = 2.25:1? Answer: nowhere!

XMTR--tuner---1 WL 75 ohm coax---50 ohm load

And the answer would be different still in this circuit.

XMTR---1/4 WL 75 ohm coax---50 ohm load

Amazin', what happens when you change the circuit!

ac6xg

Jim Kelley wrote:


Cecil Moore wrote:

Here's the example sans the Bird. Between the tuner output
and the load, where exactly is the actual SWR = 1:1 and where
exactly is the actual SWR = 2.25:1? Answer: nowhere!

XMTR--tuner---1 WL 75 ohm coax---50 ohm load

And the answer would be different still in this circuit.

XMTR---1/4 WL 75 ohm coax---50 ohm load

No, it wouldn't. The answer is exactly the same. *NOWHERE* is
the SWR 1:1 or 2.25:1. In both examples, the SWR on the coax
is 1.5:1. The SWR is *always* set by the relationship of Z0
to the load. In both examples above, that relationship is
*identical*.

Amazin', what happens when you change the circuit!

Z0 didn't change. The load didn't change. Therefore, the
SWR didn't change. What exactly do you think changed?
--
73, Cecil http://www.qsl.net/w5dxp

"Cecil Moore" wrote in message
. ..
Jim Kelley wrote:


Cecil Moore wrote:

Here's the example sans the Bird. Between the tuner output
and the load, where exactly is the actual SWR = 1:1 and where
exactly is the actual SWR = 2.25:1? Answer: nowhere!

XMTR--tuner---1 WL 75 ohm coax---50 ohm load

And the answer would be different still in this circuit.

XMTR---1/4 WL 75 ohm coax---50 ohm load

No, it wouldn't. The answer is exactly the same. *NOWHERE* is
the SWR 1:1 or 2.25:1. In both examples, the SWR on the coax
is 1.5:1. The SWR is *always* set by the relationship of Z0
to the load. In both examples above, that relationship is
*identical*.

Amazin', what happens when you change the circuit!

Z0 didn't change. The load didn't change. Therefore, the
SWR didn't change. What exactly do you think changed?
--
73, Cecil http://www.qsl.net/w5dxp

obviously the problem here is that cecil thinks he is the only one that
knows better than to try to measure reflected power with a 50 ohm meter in a
75 ohm coax.

Dave wrote:
obviously the problem here is that cecil thinks he is the only one that
knows better than to try to measure reflected power with a 50 ohm meter in a
75 ohm coax.

From your posturing, it wasn't readily apparent to me that
you were agreeing with me.
--
73, Cecil http://www.qsl.net/w5dxp

"Cecil Moore" wrote in message
. ..
Dave wrote:
obviously the problem here is that cecil thinks he is the only one that
knows better than to try to measure reflected power with a 50 ohm meter
in a 75 ohm coax.

From your posturing, it wasn't readily apparent to me that
you were agreeing with me.
--

i'm not agreeing with how you assume the 50 ohm impedance of the meter out
of the circuit. 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. obviously it will not measure any reflected power which
is perfectly correct for the whole circuit as defined and as actually
measured.

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? I also think that if you
change the circuit, it's possible to measure the effect of that change.
The meter measures what takes place at its insertion point in the
circuit. What you seem to be upset about is that it might not in every
case accurately display the conditions at some arbitrary position away
from its insertion point. Like within a shorted quarterwave stub for
example. Are you still unwilling to accept that the meter itself can
present a perturbation?

ac6xg

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).
--
73, Cecil http://www.qsl.net/w5dxp

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