[Elecraft] Rescaling the W2?

[Alan]

I just read out the power via RS-232 with the calibration at the nominal 
value of 500 and then again with the bogus calibration value to see how 
much it changed.  The calibration value is not linear - I think it is 
proportional to the detector voltage, which is roughly proportional to 
power squared.  (650/500)^2 = 1.69 and I measured 1.6.

Alan N1AL


On 11/20/2015 09:44 AM, Cliff Frescura wrote:
> Very cool Alan!  Did you verify the power with another reference meter?
> ...wondering if the scale adjustment is linear over the calibration setting
> range.
>
> 73,
>
> Cliff K3LL
>
> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Alan
> Sent: Friday, November 20, 2015 9:07 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] Rescaling the W2?
>
> I just tested it.  The maximum you can set the W2 calibration value to is
> 650.  (Using the ">" and "+" RS-232 commands)  That causes the wattmeter to
> read about 60% high on my W2.  So with the W2 set to read 2000W full scale,
> the actual full scale would be about 1250W.
>
> Or you could go in the other direction.  The minimum calibration value is
> 350, which causes the power to read about 47% (on my unit).  With the
> W2 set to read 200W full scale it would actually be about 425W full scale.
>
> Alan N1AL
>
>
> On 11/20/2015 07:15 AM, Cliff Frescura wrote:
>> I find the scaling awkward as well.  My W2 is placed on the input side
>> of my
>> KPA500 and it seems that dividing the scale by two might do the trick.
>> I've not looked at the schematic, but wonder if it could be tricked by
>> a resistor divider in the sensor line.
>>