[EMAIL PROTECTED] writes: Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang ---------------------------------------------------------------------- Carl -
If you have a VTVM or DMM with a 10-11M input impedance, all you need is an RF probe. <http://www.io.com/~n5fc/rfprobe2.htm> Measure the RF voltage across your dummy load, (after measuring what IT really is in ohms,) and calculate power. So if your RF voltmeter reads 71V RMS at 14.1 MHz and your load is exactly 50 ohms, your meter should read 100W. E= sqrt(P*R) or 100 * 50 = 1500 sqrt = 70.71 VRMS. The Drake wattmeters are pretty good, about as good as any of that type of meter. (Breune circuit) They are by definition, NOT precision meters, being specified as +/- 5% of _reading_, +2W on the 200W scale, i.e., +/- 7 Watts when reading 100W. They also can vary +/- 5% from band to band. Of course ANY standing waves on the coax will add (or subtract!) from these errors. You can then reverse the connections to the wattmeters and calibrate the Reflected scale the same way. By the way, do NOT put them all in series to calibrate, one at a time with short coax jumpers. And no, you can't have too many black boxes.....! 73, Garey - K4OAH **************Get the scoop on last night's hottest shows and the live music scene in your area - Check out TourTracker.com! (http://www.tourtracker.com?NCID=aolmus00050000000112)
