# Question regarding return loss formula

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Could some electronics guru here please clarify this ? Since my engineering school days,  I have been told that the return loss(e.g., for an antenna) is
RL = -20.0log(|gamma|)  where gamma is the reflection coefficient.However,
recently I have come across journal articles, papers  where the authors use:
RL = 20.0log(|gamma|), i,e,,  the negative sign is missing. Which of these two is  correct ?

Re: Question regarding return loss formula

ng school days,  I have been told that the return loss(e.g., for an antenna
) is

er,
se:

ese two is  correct ?

https://en.wikipedia.org/wiki/Return_loss#Sign

Re: Question regarding return loss formula
On 2020-09-19 11:49, amal banerjee wrote:

This almost funny. You should be able to work that out for
yourself. Do you worry about the sign of the loss of attenuators
too?

Jeroen Belleman

Re: Question regarding return loss formula
On Sat, 19 Sep 2020 14:16:41 +0200, Jeroen Belleman

Neither antennas nor attenuators usually return more power than you
send them. I suppose their return loss is positive and their return
gain is negative.

--

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

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Re: Question regarding return loss formula
On 2020-09-19 05:49, amal banerjee wrote:

The one with the minus sign is the return loss, the one without is the
return gain.  In a passive system, the loss in dB is positive, while the
gain in dB is negative.

Unless you're building reflection amplifiers, no confusion is likely to
result.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs
Principal Consultant
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Re: Question regarding return loss formula
On Sat, 19 Sep 2020 11:36:41 -0400, Phil Hobbs

Wiki says that return loss of a lossy device is positive in dB.

https://en.wikipedia.org/wiki/Scattering_parameters#Input_return_loss

Tunnel diode RF amps needed a circulator to separate the input from
the output.

--

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

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Re: Question regarding return loss formula
On Saturday, September 19, 2020 at 1:03:38 PM UTC-4, snipped-for-privacy@highlandsniptechnology.com wrote:

A negative gain is a positive loss. A negative loss is a positive gain. OMG- semantics!

Re: Question regarding return loss formula
On 2020-09-19 13:03, snipped-for-privacy@highlandsniptechnology.com wrote:

Well then we agree.  I feel so validated. ;)

Cheers

Phil Hobbs

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Dr Philip C D Hobbs
Principal Consultant
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Re: Question regarding return loss formula
On 9/19/2020 10:36 AM, Phil Hobbs wrote:

I disagree, Phil. I think you have them backwards.

Re: Question regarding return loss formula
On 2020-09-19 15:31, John S wrote:

A really well matched system might have a return loss of (plus) 30 dB.  No?

Cheers

Phil Hobbs
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Dr Philip C D Hobbs
Principal Consultant
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Re: Question regarding return loss formula
On 9/19/2020 8:56 PM, Phil Hobbs wrote: