Eric and all, That 50 ohm power resistor you are using will be highly inductive - it is a wirewound type, meaning it is a coil of resistive wire. Yes, it measures 50 ohms at DC, but for AC, the resistive (and reactive) value depend on the frequency of operation.
For those wishing to save a buck on a dummy load, check out the power film resistors by Caddock (MP series), they are non-inductive up to 500 mHz - Mouser carries them priced from about $3 to $9 depending on the rating. They are available in power ratings from 15 to 100 watts, but must be used with an adequate heatsink - the 15 watt is derated to 1.5 watts without a heat sink and the 60 watt version is derated to 3.5 watts. An easy to find source of heat sink material is computer CPU coolers. See Tom Hammond's website www.qsl.net/n0ss for one implementation. You can see the reisitors themselves at www.mouser.com/caddock. Another alternative is the Elecraft DL1 mini-kit - a good 50 ohm load with a built in tap for connecting the DMM to measure voltage and calculate the power. 73, Don W3FPR Life is what happens when you are making other plans ----- Original Message ----- In an attempt to save pennies, I got a 10W 50 ohm resistor ($1.79 for two) at the Shack and soldered it to a male BNC--I figured this would make a serviceable QRP dummy load. The resistor checked out at 50.0 ohm on my DMM. When I hooked this to my KX1 and went through the ATU alignment procedure (nulling C9, etc), I only get an apparent out put of about 0.3W (according to the display on the radio). Ditto when I tune my G5RV--I get to 1:1.1, but with only 0.3W. (This antenna/feedline system is tunable by my LDG Z100 to 1:1; see below.) _______________________________________________ Elecraft mailing list Post to: [email protected] http://mailman.qth.net/mailman/listinfo/elecraft You must subscribe to post. Subscriber Info (Addr. Change, Unsub etc): http://mailman.qth.net/subscribers.htm Elecraft page: http://www.elecraft.com
