Ron, Use a diode detector. A 1N4148 diode will do fine up to about 12 watts. Connect the anode of the diode to the center conductor of your coax *at* the dummy load (use a coax TEE adapter if you have no other access). From the cathode end of your diode, connect a 0.01 uF capacitor to the shield side of the coax. Your DMM leads connect across the capacitor.
Measure the forward voltage of the diode with your DMM if it has that function, otherwise, assume that the diode forward voltage is 0.6 volts. With this probe, the DVM will read the peak RF voltage. You can calculate the power from the DMM reading as follows: The peak voltage across the resistor is equal to the DVM reading plus the diode forward voltage, so add them. You may then calculate the RMS value of the result above. Then square that result and divide by the resistance. Or you may accept (or derive) the formula will be as follows with no intermittent RMS calculation. P = (Vdvm+Vdiode)^2/2R = (Vdvm+Vdiode^2/100 for a 50 ohm dummy load OR, if you assume the diode drop is 0.6 volts P=(Vdvm+0.6)^2/100 73, Don W3FPR Ron Bower wrote: > I have searched the archives and have not been able to find a definitive > answer. > > > > I've now completed the construction of the basic KX1 and would like to have > a fairly reasonable measurement of the output power on 20M and 40M > > > > I have a very decent dummy load but do not have a very accurate RF Power > meter. I do have a decent DMM and could measure the voltage drop across the > 50 ohm dummy load - I'm not sure how accurate the DMM would be at 7 or 14 > MHZ. > > > > Is there a recommended method to measure the power output without an RF > power meter ? > > > > Thanks in advance, > > Ron, AC2C > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
