[Elecraft] W2 Questions

[Phil Hystad]

Paul,

Thanks for your comments.  And, in followup, if Elecraft were to make
a meter with reasonably high accuracy I presume that another display
method, other then LEDs, would be required.  I think a high-resolution
LCD with nice color graphic renditions of power information.  OK, sort
of kidding here, I presume that a computer interface could handle that
kind of information display.

peh

On Dec 9, 2009, at 5:23 PM, Paul Christensen wrote:

> Phil,
> 
> With each LED representing 100-watts on the 2KW scale, it may be of some 
> help to go from 10% to 5% in accuracy, but in the case of the W2, the 
> display resolution is limited to 50-watts in between mid power ranges (e.g., 
> 250-watts) but a display of 200-watts with two LEDs showing may actually 
> mean 151 watts or 249 watts.
> 
> 50-watts is mid-way between any two LEDs at the 2KW range and I'm making an 
> assumption that levels less than any 50-watt range (e.g., 240-watts) will 
> result in the preceding element being lit which shows 200-watts.  If it's 
> more than the mid point (e.g., 260-watts) then the next LED should be lit. 
> So, at the low-end of the W2's range at say the 200-watt level, the meter 
> can at best resolve to only 50/200 = 25% and seemingly 100/200 = 50% at 
> worst (using the 149W to 249W example).  I don't want to confuse resolution 
> with accuracy but the two parameters go hand-in-hand.  That said, I see no 
> real benefit of going from 10% to 5% in accuracy when resolution 
> deficiencies can easily mask the error in accuracy.  I may be completely 
> wrong with the manner in which the W2 resolves, so someone set me straight 
> if my assumptions aren't correct.
> 
> You asked the question about what it takes to achieve better accuracy.  You 
> may want to read N8LP's excellent article in QEX from a few years ago, along 
> with articles from Warren Bruene, Roy Lewallen,  John Grebenkemper, and 
> others who have published on the accuracy subject.
> 
> Paul, W9AC
> 
> 
> ----- Original Message ----- 
> From: "Phil Hystad" <k7peh at comcast.net>
> To: "Elecraft" <elecraft at mailman.qth.net>
> Sent: Wednesday, December 09, 2009 7:51 PM
> Subject: [Elecraft] W2 Questions
> 
> 
>> A few questions about the W2 meter:
>> 
>> 1.  The posted accuracy is +- 0.5 dB which I calculate as about +- 12 %. 
>> Is this full scale accuracy and if so is half scale possibly more accurate 
>> or is this the most accurate the meter is likely to be.  I am not even 
>> sure if it makes a difference for full scale or half scale for a digital 
>> meter so that part of my question may be moot.
>> 
>> 2.  What does it take to achieve an accuracy better then 5 % (for 
>> example), and is it possible to achieve an accuracy of 1 % or better?  I 
>> am curious as to where the money needs to be spent in achieving such 
>> accuracy.  Is it in the directional coupler?
>> 
>> 3.  I am thinking that the company that can build the best receiver on the 
>> market (the K3) can also build the best meter.  So, would Elecraft 
>> principles consider a future super-accurate, best on the planet, amateur 
>> radio RF/SWR power meter?  Oh, I think a current meter would be cool too.
>> 
>> And, I know that having meter accuracy is of little importance in ham 
>> radio but there is some kind of deep seated quirk in me that wants 
>> accuracy just for the heck of it.  Certainly 5 % is achievable, right?
>> 
>> 73,
>> phil, K7PEH
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