One more time.
It was a WORST CASE calculation which placed an upper bound on the possible
loss
from operating into a 1.7:1 SWR as opposed to a 1:1 SWR.
In practice most of the power is eventually radiated.
sheesh!
H.


"Cecil Moore" wrote in message
...
Fred W4JLE wrote:
I would disagree with your statement about SWR being absorbed in the
source.
The reflected wave is rereflected and aside from losses caused by the 2
way
trip is reradiated.

Reflected current flowing into the final amp can superpose in
phase with the forward current and, without protection circuitry,
cause the final amp to exceed its dissipation rating.

Another possibility is when the reflected voltage superposes
in phase with the forward voltage, and without protection
circuitry, exceeds the voltage rating of the final.

If all reflected power was always re-reflected, there would
be no need for protection circuitry. The generated power is
*defined* as the forward power minus the reflected power. That
does NOT mean that the reflected power is 100% re-reflected.
--
73, Cecil http://www.qsl.net/w5dxp

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H. Adam Stevens, NQ5H wrote:
One more time.
It was a WORST CASE calculation which placed an upper bound on the possible
loss
from operating into a 1.7:1 SWR as opposed to a 1:1 SWR.
In practice most of the power is eventually radiated.
sheesh!
H.

Please give us the conditions (cable Z0, load Z, or whatever you need)
that cause this "worst case" to occur.

Roy Lewallen, W7EL

"Roy Lewallen" wrote in message
...
H. Adam Stevens, NQ5H wrote:
One more time.
It was a WORST CASE calculation which placed an upper bound on the
possible
loss
from operating into a 1.7:1 SWR as opposed to a 1:1 SWR.
In practice most of the power is eventually radiated.
sheesh!
H.

Please give us the conditions (cable Z0, load Z, or whatever you need)
that cause this "worst case" to occur.

Roy Lewallen, W7EL

See other post.

H. Adam Stevens, NQ5H wrote:

One more time.
It was a WORST CASE calculation which placed an upper bound on the possible
loss from operating into a 1.7:1 SWR as opposed to a 1:1 SWR.
In practice most of the power is eventually radiated.

As Roy, W7EL, previously indicated:

Power reflection coefficient:
rho^2 = [(SWR-1)/(SWR+1)]^2 = 0.067 = Pref/Pfor

1-rho^2 = 0.933 = 93.3% forward power delivered to the load

93.3 watts is 0.3 dB down from 100 watts.

The log of the ratio of two SWRs doesn't seem to have much
meaning.
--
73, Cecil http://www.qsl.net/w5dxp

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It's called db, Cecil.


"Cecil Moore" wrote in message
...
H. Adam Stevens, NQ5H wrote:

One more time.
It was a WORST CASE calculation which placed an upper bound on the
possible
loss from operating into a 1.7:1 SWR as opposed to a 1:1 SWR.
In practice most of the power is eventually radiated.

As Roy, W7EL, previously indicated:

Power reflection coefficient:
rho^2 = [(SWR-1)/(SWR+1)]^2 = 0.067 = Pref/Pfor

1-rho^2 = 0.933 = 93.3% forward power delivered to the load

93.3 watts is 0.3 dB down from 100 watts.

The log of the ratio of two SWRs doesn't seem to have much
meaning.
--
73, Cecil http://www.qsl.net/w5dxp

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H. Adam Stevens, NQ5H wrote:

"Cecil Moore" wrote:
The log of the ratio of two SWRs doesn't seem to have much
meaning.

It's called db, Cecil.

The IEEE Dictionary says the ratio of power, voltage, and
current can be expressed in dB. It specifically states
that dB can only be related to power ratios or to parameters
that are proportional to the square root of power ratios.

SWR1 = [SQRT(Pfor1)+SQRT(Pref1)]/[SQRT(Pfor1)-SQRT(Pref1)]

SWR2 = [SQRT(Pfor2)+SQRT(Pref2)]/[SQRT(Pfor2)-SQRT(Pref2)]

The ratio of two SWRs will not reduce to a power ratio or
to the square root of a power ratio.
--
73, Cecil http://www.qsl.net/w5dxp

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Yes, SWR is a dimensionless quantity. dB is, as far as I know, defined
only for power, voltage and current ratios, as the IEEE Dictionary
implies. Since it's defined differently for power than for voltage or
current (so that an increase or reduction in one quantity represents the
same number of dB increase or decrease in the other), anyone using it
for something else would have to clarify how it would be defined in that
context.

Roy Lewallen, W7EL

Cecil Moore wrote:
H. Adam Stevens, NQ5H wrote:

"Cecil Moore" wrote:
The log of the ratio of two SWRs doesn't seem to have much
meaning.

It's called db, Cecil.


The IEEE Dictionary says the ratio of power, voltage, and
current can be expressed in dB. It specifically states
that dB can only be related to power ratios or to parameters
that are proportional to the square root of power ratios.

SWR1 = [SQRT(Pfor1)+SQRT(Pref1)]/[SQRT(Pfor1)-SQRT(Pref1)]

SWR2 = [SQRT(Pfor2)+SQRT(Pref2)]/[SQRT(Pfor2)-SQRT(Pref2)]

The ratio of two SWRs will not reduce to a power ratio or
to the square root of a power ratio.