As has been clearly demonstrated in this thread, there are multiple methods of measurement. The one that gets my vote for elegance is the one with two tuners back-to-back. With respect to the method that measures temperature rise, taking into account the mass of the tuner, one also needs to take into account the specific heat capacity of the tuner. One kilo of material x doesn't heat up at the same rate as one kilo of material y when the same heating power is applied. The tuner will of course be a mix of materials, so one would have to measure the rate at which the tuner heats up when heat is applied through a know heating source rather than TX power. If it is done that way, one needs to know neither the mass nor the specific heat capacity, since what one is measuring is essentially the mass times the specific heat capacity.
73, Erik K7TV -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Ron D'Eau Claire Sent: Saturday, March 10, 2012 11:47 AM To: 'Rick Stealey'; elecraft@mailman.qth.net Subject: Re: [Elecraft] high-power tuner I was investigating tuner losses a few years ago and ran into many of these same questions. A physicist buddy pointed out to me that the normal approach to measure loss in something like a tuner is to put it in a well-insulated chamber and measure the rise in temperature over time while transmitting. From there on can calculate the energy required to cause the temperature rise which can be used to calculate the number of watts of RF that never make it through the box. 73, Ron AC7AC -----Original Message----- There seems to have been no answer as to how to accurately measure the loss in a tuner. Here is a solution but requires two tuners or at least one calibrated one that could be used to measure others. Take first tuner and tune it into the mismatch, say 600 ohms. Use an antenna analyzer. Then remove the load, and connect another tuner to the output of the first (back- to-back - antenna port on first to antenna port on second tuner.) Then put a 50 ohm load on the second tuner where the transceiver would be connected, and tune the second tuner to a match. It will have the same settings as the first tuner, complete symmetry. Then measure the power in the 50 ohm load to get the loss. Since both tuners are matching the same load, and the system is symmetrical the loss contribution by each tuner is half. Repeat for other types of loads, and now you have a calibrated tuner to use with any tuner you want to test. Rick K2XT ______________________________________________________________ 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 ______________________________________________________________ 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
