[Elecraft] Feature wanted for W2 wattmeter

[Myron WVØH]

Since this has historically been a can of worms, (it created a firestorm of emails back in 2010 on a yahoo group between W5DXB, R. Fry, K1TTT, W7EL, and Owen Duffy, then VK1OD) I want to introduce an authority on power measurement. Agilent (now called Keysight) has a three part document that talks about power measurement, the usefulness of these documents depends upon your level of understanding and application but since we can all add and subtract, eqn 2-21 of this document indicates that the power delivered to the load (with all of the assumptions listed) is the forward (incident) power minus the reflected power.

http://cp.literature.agilent.com/litweb/pdf/5988-9215EN.pdf

Myron WVØH
Printed on Recycled Data

> On Jan 13, 2015, at 1:45 AM, David Woolley <forums at david-woolley.me.uk> wrote:
> 
> As well as not all the reflected power being re-reflected, the forward power measured by the coupler is not the first time forward power, but the sum of all the re-reflected power, as well.
> 
> -- 
> David Woolley
> Owner K2 06123
> 
>> On 13/01/15 01:19, Fred Jensen wrote:
>> Well ... sort of.  Some of the reflected power heats up the ATU and/or
>> PA depending on the match it sees [actually, some of the forward power
>> does too, tuners have forward losses].  "Delivered Power" is somewhat
> 
>> 
>>> On 1/12/2015 4:46 PM, Phil & Debbie Salas wrote:
>>> 
>>> Actually, "delivered power" is pretty much what you are measuring.
>>> Remember that reflected power is re-reflected by the source and adds
>>> back into the forward power.  So in your example, you are transmitting
>>> 1200 watts, having 200 watts reflected, then the 200 watts is
>>> re-reflected by the source giving you the 1200 watts.  Of course, there
>>> will be transmission line SWR-related losses.
> 
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