Steve Thompson wrote:
>On Thursday 04 April 2002 09:56, Ian White, G3SEK wrote:
>mega snip
>> Case 1. Directional coupler terminated by a transmission line and
>> mismatched load; theory based on forward and reflected waves.
>>
>> Case 2. Directional coupler terminated by a lumped-component load;
>> theory based on the relationship between voltage and current at a single
>> point - NO transmission-line concepts to be used in this theory!
>The directional coupler is the section of transmission line, and reflections
>occur at its output end.
That's only one particular type of directional coupler. Something like a
Bruene bridge doesn't have any internal transmission line, and can be
considered as making true single-point samples of current and voltage.
>It doesn't matter whether or not there's any more
>transmission line downstream - there's just an impedance presented at the
>output.
That was my whole point. Case 2 can - and should - be solved without
thinking about transmission lines, either outside or inside the
directional coupler.
--
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
New e-mail: g3sek@ifwtech.co.uk
New website: http://www.ifwtech.co.uk/g3sek
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