[AMPS] Re:

[Tom Rauch]

> >Now there is nothing wrong with using a scope, assuming you have 
> >one with the required accuracy and resolution and a good load, but 
> >it is not a good instrument for use in antenna system to measure 
> >power. Errors in power readings occur at both the square of the 
> >voltage reading error as well as proportional to load impedance 
> >error.
> 
> €  and an ordinary wattmeter would not be subject to such errors, Tom?   

SWR error is minimized if you know how to use the meter Rich. 

You read reflected power near full scale using the proper slug, and 
subtract reflected power from forward. The result is the actual 
power keeping in mind the directivity error of the slug and the 
calibration errors. 
 
> >There is absolutely nothing wrong with using a good meter. A few 
> >people have wrongly assumed a storage system can't respond fast 
> >enough, but that is certainly not correct. The storage system has 
> >to track the envelope change rate that follows audio, not the RF 
> >cycle change rate. A meter with directional coupler also remains 
> >accurate over reasonable load impedance errors. You simply 
> >deduct reflected power from forward power.
> >
> €  Can you explain why this is true?

Yes. 

Many textbooks can also, as well as the Bird manual.


73, Tom W8JI
w8ji@contesting.com

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