I can think of a few ways to investigate a tuner's efficiency. Google searching can probably give more.
You can read the inductor and capacitor values selected by the 998 and then do a circuit simulation of the L network and determine current through the inductors to find their ohmic losses. Second, you can connect known non-inductive resistors (of different values, throw in some inductance or capacitance too) as the output load and then with an RF voltmeter determine the voltage across the load and then calculate the power out. You will have to calculate the phase angle of your load as well if its not purely resistive. This method could be done using low power so its easier to build the output loads. You could probably also measure the temperature rise of the tuner in operation (put it in an insulated box). Granted, there may not be a simple off the self instrument to do it, but it can be done! 73 - Mike WA8BXN -------Original Message------- From: WILLIS COOKE Date: 3/9/2012 5:31:30 PM To: W5RDW; [email protected] Subject: Re: [Elecraft] high-power tuner I wonder how those that claim a certain efficiency for a MFJ-998 or any other antenna matching device are measuring the output power. No watt meter that I know including the famous and antique Bird can measure power with any degree of accuracy unless the load is very near the nominal value (usually 50 ohms). If you need a tuner, your antenna does not meet this criteria so, what are you using to form your opinion? I suppose that you could compare two tuners for a relative efficiency by using the same transmitter and antenna and a field strength meter. Of course, if you are running near the rated power, you can watch for smoke and get a one time opinion that the device was not efficient enough to survive. Willis 'Cookie' Cooke K5EWJ & Trustee N5BPS, USS Cavalla, USS Stewart ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
