[Amps] SWR and amplifiers

[donroden at hiwaay.net]

Just like the clock that is only correct twice a day, even the highly  
regarded Bird 43 "wattmeter" isn't always measuring what you think it  
is measuring.

Don W4DNR



Quoting Bill Turner <dezrat at outlook.com>:

> According to Ron, K4INM, (original post below) my hypothetical
> transmitter is putting out 1000 watts but only 900 is actually
> radiated into space. The 100 watt difference is lost in the
> transmission line. Correct?
>
> OK, lets suppose I have a superconductive transmission line,
> cryogenically cooled conductors with a vacuum dielectric, zero loss.
> The SWR is still the same, reflected power is the same, but now where
> does the lost power go? Would my SWR meter still show 1000 forward and
> 100 reflected?
>
> 73, Bill W6WRT
>
> **********************************************************************************
>
> Here is Ron's original post:
>
>  Do not worry about the confusion, it is all too common among HAMs
> even
> highly seasoned ones, to get this wrong.
> You will soon here the opposite of the following here, but they are
> wrong.
>
>    The amplifier outputs 1,000 Watts.
>
>    900 Watts minus "transmission line loss" X 1.0 is radiated.
>
>    100 Watts are reflected by a line to "load mismatch" back to the
> "generator" the amplifier (the only cause of any SWR) or reflected
> power.  This power when it reaches the (generator" the amplifier)
> finds
> a source impedance of under one Ohm, so it is reflected back up the
> transmission line experiencing a "transmission line loss" X 2.0 where
> 90% of that power is radiated.
>
>    10 Watts are reflected by a line to "load mismatch" back to the
> amplifier finding a source impedance of under one Ohm, so it is
> reflected back up the transmission line experiencing a "transmission
> line loss" X 2.0 where 90% of that power is radiated.
>
>    1.0 Watts are reflected by a line to "load mismatch" back to the
> amplifier finding a source impedance of under one Ohm, so it is
> reflected back up the transmission line experiencing a "transmission
> line loss" X 2.0 where 90% of that power is radiated.
>
>    0.1 Watts are reflected by a line to "load mismatch" back to the
> amplifier finding a source impedance of under one Ohm, so it is
> reflected back up the transmission line experiencing a "transmission
> line loss" X 2.0 where 90% of that power is radiated.
>
>    100% of the generated power is either radiated or turned into heat
> from the transmission line (and balun + antenna wire) losses.  (mostly
> resistive)
>
>    None of the forward power stays in the amplifier, although the
> reflected power does change the "loading" of the amplifier, changing
> it's operating conditions, from what it was with a pure reactive-less
> resistive load.
>
> --
>    Ron  KA4INM - Youvan's corollary:
>                  Every action results in unwanted side effects.
>
>
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