Sure, Fran, an O'scope is a good way to measure the voltage. I'd suggest a good 10:1 probe on that scope instead of driving the vertical input directly. Many scopes have a 50-ohm termination at their input that can throw the readings way off since the rig would see 25 ohms looking into both of the scope and dummy load in parallel. Also, the scope termination is not designed to dissipate any power and you'd likely destroy it with any significant power. The 10:1 probe isolates the scope from the dummy load.
Divide the Vp-p reading you measure with the scope by 2.82 to get Vrms and go from there: (Vrms)^2/50 = watts. Ron AC7AC -----Original Message----- Okay, I guess I left out some critical details from my original post. I am using a 50 ohm load that is intended to be used to convert test equipment from hi-impedence input to 50 ohms. It is labled 50 ohms and measures 50 ohms with my DMM. It should be purely resistive and I do not have any equipment to prove that it is. The need to load it properly using the KAT2 was only because I wanted the KAT2 in-circuit for improved forward power measurement within the K2. I knew that it would need to load things to cancel itself out. Based upon what Ron, Don and Jack have said, I guess that I should remove the KAT2 and RF probe and try something similar to what I tried last time I attempted to understand how well this radio tracks against the published specifications. Would it be reasonable to just place a short piece of coax between the load and an O'Scope, measure the peak-to-peak voltage, divide by 2*SQRT(2) and go from there? Would this require knowing the coax velocity factor and dealing with prioper lengths of coax based upon wavelength (half or quarter) at the different frequencies? I ask these questions because last time I tried using my Scope to make these measurements, the measurements were obviously incorrect because they indicated that my rig was way more than 100% efficient. What I expect is that I can make apropriate measurements at 3 points on each band and see that I get no more that 10% variation across said band and from band-to-band. I expect that I have a problem on 10 Meters because I am getting a HiCur indication at 3 amps when set for 10 watts, so something needs changing there. However, until I have trustable measurements on the other bands, I expect that untangling the issues will be impossible. Help from the experts is needed on how to make such measurements without fancy RF power meters. Obviously a purely resistive 50 ohm load is the first requirement, and I believe that I have that. 73, Fran _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
