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#11
September 29th 15, 08:45 PM
posted to rec.radio.amateur.antenna
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Parallel coax
"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? 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. 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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