power output of K2

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power output of K2

Ian Stirling, G4ICV, AB2GR
  I haven't been too happy with the power output
of my K2, but I didn't know if my vintage 1979
Heathkit power meter is reading low.
  Today, I used an oscilloscope and measured
70.4 Volts peak to peak at 1.817 MHz into a
50 ohm dummy load with the meter indicating just
under 10 Watts.
  I trust the calibration of the 'scope more than
the meter.
  That 70.4 Volts peak to peak is 12.4 Watts;
my Heathkit meter is reading low.

Ian, G4ICV, AB2GR, K2 #4962
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RE: power output of K2

Don Wilhelm-3
Ian,

That just amplifies my distrust of wattmeters.  If you were on a 100 watt
scale and the wattmeter spec is as good as 5% of full scale, you could
expect an error of up to 5 watts (either high or low) - most amateur grade
wattmetrs are speced for 10% of full scale (or even 20% in some cases), so
since you were only 2.4 watts in error, that wattmeter is doing pretty good
at the power range you were using.

An RF Probe or 'scope to measure the RF Voltage along with an accurate
non-reactive 50 ohm dummy load will provide much better accuracy (except
when the wattmeter has been properly calibrated at the power output that it
is being used to test the K2.

73,
Don W3FPR

> -----Original Message-----
>
>   I haven't been too happy with the power output
> of my K2, but I didn't know if my vintage 1979
> Heathkit power meter is reading low.
>   Today, I used an oscilloscope and measured
> 70.4 Volts peak to peak at 1.817 MHz into a
> 50 ohm dummy load with the meter indicating just
> under 10 Watts.
>   I trust the calibration of the 'scope more than
> the meter.
>   That 70.4 Volts peak to peak is 12.4 Watts;
> my Heathkit meter is reading low.
>
> Ian, G4ICV, AB2GR, K2 #4962
> --
>

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Re: power output of K2

Ian Stirling, G4ICV, AB2GR
On Tuesday 21 February 2006 18:25, Don Wilhelm wrote:

> An RF Probe or 'scope to measure the RF Voltage along with an accurate
> non-reactive 50 ohm dummy load will provide much better accuracy (except
> when the wattmeter has been properly calibrated at the power output that it
> is being used to test the K2.

Don,

  There's another suggestion, thankyou.
I'll try using a digital volt meter,
eleven megohms input impedance, with the
probe I made during my K2 construction.
  It will be an interesting cross check.

Ian, G4ICV, AB2GR, K2 #4962
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