[Elecraft] KPA-500 watt meter vs. Palstar

[k2zf50 at aol.com]

Hi Ray,


Thanks or your response. I have found that on 20 meters my K3 displays a high current warning above 80 watts displayed on the K3. Other bands I can transmit at 100 watts and no high current warning. I believe that is because the watt meter I have been using is not accurate and the K3 may be putting out in excess at this power level displayed on the K3 meter and therefore the high current warning. That is why I was asking which watt meter, the Palstar or the KPA-500 would be more accurate. I understand that 80 watts or 110 watts on the receiving end is not noticeable but I need to know why the high current warning at 80 watts on the K3? Is it the watt meter I am using to calibrate the K3?



Thanks,


Jim Douglas  K2ZF



-----Original Message-----
From: Ray Sills <raysills3 at verizon.net>
To: k2zf50 <k2zf50 at aol.com>
Sent: Sun, Sep 18, 2011 5:22 am
Subject: Re: [Elecraft] KPA-500 watt meter vs. Palstar


HI Jim:

Well, as always, measuring equipment has to be calibrated, and as  
you've noticed, indicated readings can vary over the range of  
operation.  Most measuring gear for ham use has about a 10% or so  
tolerance, plus and minus, so you can't get truly accurate readings.
To get to precision levels, (1% or so), you need very high quality  
instruments (meaning expensive), or at least a way of correlating the  
indicated readings to a know level of accuracy.

For many hams Bird wattmeters are the reference measurement, but even  
they are not highly accurate, and it's often the case that the  
accuracy varies over the range of operation.  The fact that the  
Elecraft unit has a digital display does not mean it's more  
accurate.  It may be more "precise" (able to finely resolve a  
measurement), but that does not mean it's more accurate.  A digital  
clock that displays seconds is more precise than an analog clock that  
has only a minute hand and hour hand, but the digital clock might  
have a bad time base and drift enough to gain or lose time in a day.   
The analog clock might be rock solid, and very accurate.. just not as  
precise.

So, with regard to your measurements... take your pick.  If you want  
to be a scientist, you can build a dummy load in a can, fill it with  
de-ionized (pure) water,  and measure the temperature change over  
time of the water to determine how many watts are being dissipated.   
Then, make a comparison to what the meter says and construct a  
calibration chart.

For me, that would be a lot of work.  I'd be happy with approximate  
readings... if the 100 watt reading is actually 85 watts or 110  
watts, it would not bother me.  You'd hardly notice the difference at  
the receiving end, maybe not at all.

73 de Ray
K2ULR
FN20kf
Warrington, PA


On Sep 18, 2011, at 8:58 AM, k2zf50 at aol.com wrote:

>
> Hi,
>
>
>
> My KPA-500 watt meter and my Palstar watt meter read about the same  
> at the higher power readings. But at the 100 watt and lower ranges  
> there is a significant difference. My question is which is the more  
> correct reading at the lower ranges, the Elecraft or Palstar. If I  
> want to calibrate my K3 which one would be more accurate? Being  
> that the Elecraft is a digital display would that one be more  
> accurate?
>
>
> Thanks,
> Jim Douglas  K2ZF
>
>
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