Re: Measuring power

KB9BVN - <kb9bvn@...>

If I measure my HT20 into a dummy load with my WM2 power meter, I see close to 7 watts.  Perfect situation. 

If I measure my HT20 into my attic dipole thru my MFJ antenna tuner, I see close to 5 watts. Imperfect situation. 

My attic dipole is a halfwave 40m tuning it up on 20m is not real efficient anyway. 

On Wed, Apr 17, 2019 at 10:03 AM Charles W. Powell via Groups.Io <> wrote:

I don’t know about anyone else, but I am measuring power on mine, key down, using a 50 ohm dummy load, and connecting my high impedance oscilloscope leads across the load.  The scope is a a Siglent 200 mHz scope, so it is measuring far away from the rolloff.  Using the peak-to-peak voltage, I make my calculation by deriving the RMS voltage, then using RMS-squared/resistance.  So with about 13.4 DC volts input, my peak output voltage on the HT-20 was 52 volts.  ((52 * 0.707/2)^2)/50 = 6.8 watts into 50 ohms.  I get approximately the same readings with my MFJ tuner’s power readout and also my QRP-o-meter, although I don’t expect those to be nearly as accurate.

Caveats:  I might be entirely wrong in my calculations and I might be missing some subtlety in making this calculation.


Chas - NK8O

On Apr 17, 2019, at 8:29 AM, WA4EFS <himself@...> wrote:

Several posts have referred to the RF power output of QRP rigs including the Hilltopper, the relation to amplifier class, or to final transistor quality, etc.  I am curious as to how power is being measured or assessed in relation to various reports.
Thanks and 73, 

73 de KB9BVN
Brian Murrey

Join to automatically receive all group messages.