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Re: [TowerTalk] PL259 Insertion Loss?

To: "Al Kozakiewicz" <>
Subject: Re: [TowerTalk] PL259 Insertion Loss?
From: "Rick Karlquist" <>
Date: Sat, 14 Jan 2012 16:14:34 -0800
List-post: <">>
Al Kozakiewicz wrote:
>>There is a semantic misunderstanding here about the meaning of "insertion
>> loss".  Everyone on this reflector seems to think it refers to
>> dissipation loss.  It doesn't, as commonly used by connector vendors.
>> Instead it refers to what is more precisely called "transducer loss" or
>> S21 in terms of S parameters.  In a PL259 at 30 MHz, the transducer loss
>> is almost all in the form of "mismatch loss", which is a theoretical
>> number and does not produce any physical heat.  Thus 0.3 dB insertion
>> loss basically means 0.3 dB mismatch loss, or something like 6% reflected
>> power.
> Could you please explain that to me?
> This sounds like like a discussion on another forum recently where a
> fellow asserted that an SWR more than 1:1 would insure that not all power
> is transferred to a transmision line.  As near as I could tell, it sounded
> something like power factor (which, as a DC and digital logic guy, still
> mystifies me).
> Al

In measuring S parameters, you use a 50 ohm source with a certain
"available power" meaning the power the source will put into a 50
ohm load (1:1 SWR).  If the SWR > 1:1, then not all of the available
power will be transferred to the line.  As I said, this is a theoretical
number.  There are many tutorials on S parameters that you
can refer to for additional details.

Transmitters are rarely 50 ohm sources, so the previous theoretical
discussion isn't very meaningful.  I'm just trying to explain
where the connector manufacturer is coming from.

Rick N6RK



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