[Elecraft] Feature wanted for W2 wattmeter

[Walter Underwood]

A better example would be to use a 100 Ohm dummy load and match it with a tuner. Then measure the heat generated by the load. It should be 100W, minus any losses in the tuner and transmission line.

wunder
K6WRU
CM87wj
http://observer.wunderwood.org/

On Jan 12, 2015, at 9:26 PM, Vic Rosenthal <k2vco.vic at gmail.com> wrote:

> Here is an experiment to show what I mean.
> Take a transmitter and connect it to a 50 ohm dummy load through an antenna tuner. Put a wattmeter between the transmitter and the tuner.
> Now adjust the transmitter for 100 watts output and the tuner for 1:1 SWR. 
> The meter reads 100W forward and zero reflected power.
> Now adjust the tuner for an SWR of about 2.5:1. The wattmeter will show forward power of about  120 watts and reflected power of about 20 watts. Did I increase the real power output of my transmitter? Did I make my signal stronger? No.
> I want a wattmeter that has an option to indicate 100 watts in this situation.
> 
> Vic K2VCO /4X6GP 
> 
>> On Jan 13, 2015, at 6:56 AM, Walter Underwood <wunder at wunderwood.org> wrote:
>> 
>> No. That is wrong. Forward and reflected are aspects of the standing wave, not power delivered. —wunder, K6WRU
>> 
>>> On Jan 12, 2015, at 8:53 PM, Vic Rosenthal <k2vco.vic at gmail.com> wrote:
>>> 
>>> What I want is just forward - reflected. Neglecting losses, this is what the tx is 'delivering'. In real life somewhat less gets to the antenna.
>>> 
>>> Vic K2VCO /4X6GP 
>>> 
>>>> On Jan 13, 2015, at 3:19 AM, Fred Jensen <k6dgw at foothill.net> 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 difficult to calculate.  Working into a matched, non-reactive load [common for AM broadcast, at least a number of years ago], it's "I squared R" where R is the radiation resistance of the antenna ... and some minor conductor losses in the antenna.  Things get pretty sticky if it's not a matched load.
>>>> 
>>>> 73,
>>>> 
>>>> Fred K6DGW
>>>> - Northern California Contest Club
>>>> - CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
>>>> - www.cqp.org
>>>> 
>>>>> 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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