September 29th 15, 08:41 PM
posted to rec.radio.amateur.antenna
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First recorded activity by RadioBanter: May 2011
Posts: 550
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Parallel coax
On 9/29/2015 1:45 PM, Wayne wrote:
"rickman" wrote in message ...
On 9/29/2015 2:10 PM, Wayne wrote:
"rickman" wrote in message ...
On 9/29/2015 9:22 AM, Jerry Stuckle wrote:
On 9/29/2015 12:55 AM, rickman wrote:
On 9/28/2015 8:56 PM, Jerry Stuckle wrote:
On 9/28/2015 8:09 PM, rickman wrote:
On 9/28/2015 7:55 PM, Jerry Stuckle wrote:
On 9/28/2015 5:18 PM, rickman wrote:
On 9/28/2015 4:34 PM, Jerry Stuckle wrote:
snip
So stand by. Someone may be getting it for me.
I really don't give a damn. You would argue the sun rises in the west.
I have a copy of the paper.
Trevor Bird
Editor-in-ehief,Engineering
IEEE Transactions on Antennas and Propagation
CSIRO leT Centre, PO Box 76
Epping, NSW 1710, Australia
Tel: +61 2 9372 4289
Fax: +61 2 9372 4446
E-mail:
Definition and Misuse of Return Loss
Trevor S. Bird
Here is the equation from the article
Pin
RL = 10 log,10 ( ---- ) dB, (1)
Pref
The author explicitly states the resulting value will be positive when
Pin is greater than Pref. He goes on to say, "That is, return loss is
the negative of the reflection coefficient expressed in decibels."
He goes on to quote from the "IEEE Standard Dictionary of Electrical
and Electronic Terms, Fourth Edition".
(1 ) (data transmission) (A) At a discontinuity in a
transmission system the difference between the power
incident upon the discontinuity. (B) The ratio in deci-
bels of the power incident upon the discontinuity to the
power reflected from the discontinuity. Note: This ratio
is also the square of the reciprocal to the magnitude of
the reflection coefficient. (C) More broadly, the return
loss is a measure of the dissimilarity between two
impedances, being equal to the number of decibels that
corresponds to the scalar value of the reciprocal of the
reflection coefficient, and hence being expressed by the
following formula:
|Z1 + Z2|
20 log,10 |-------| decibel
|Z1 - Z2|
where Z1 and Z2 = the two impedances.
(2) (or gain) (waveguide). The ratio of incident to
reflected power at a reference plane of a network.
So is this what you "knew" the paper said? Seems to be the opposite
of what you have been promoting.
Anyone feel this paper is incorrect?
Well, it is exactly what I thought I learned on the subject. 
# To be honest, it seems logical that the power in should be the reference
# and the reflected power should be the property being measured which is
# what Jerry is saying. But clearly for this particular term "return
# loss" this is not the case.
# Does it seem intuitively correct that "return loss" should be a higher
# number when the reflection is smaller?
Yes. It is not necessarily a loss. Consider a loss-less line and a
perfect source. You still have a return loss, but there are no losses in
the system.
There seems to be a case for saying it either way.
My exposure to RL was "on the job" when playing with antennas and a
network analyzer.
We always used positive numbers and viewed RL as the difference in dB
between the forward and reflected power.
That makes perfect sense. You could never have a negative dB.
Actually, RL was something in the network analyzer data file and
printout. We pretty much ignored it and looked at S parameters and SWR.
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