I'm not convinced that toroids are inferior to air wound coils. There will be some core loss but there will be less ohmic loss as well. I'm also not sure that just getting a tuner rated at the same power level as an amplifier is always going to be most efficient. If the marketing agency is doing the tuner rating the rating may be suspect. There are some tuners that can just about match anything for an antenna. If it won't melt at a particular power level, is it the best tuner for that power level? Matching a given load usually means giving the transmitter near a 50 ohm load. If you have a tuner that does that with no antenna attached it means the tuner must dissipate all the power. Manual tuners often have some hints on how to get the best efficiency at a good match, like try to find a match using maximum or minimum value for control X. With automatic tuners, we often just let the tuner do its thing and use the match it finds. Some tuners will have better algorithms than others in picking the best match. The difference from one tuner to another can be a lot more than milliwatts. So it can be a good idea to get good evaluations of available tuners. 73 - Mike WA8BXN -------Original Message------- From: WILLIS COOKE Date: 3/9/2012 9:47:31 PM To: Elecraft Subject: Re: [Elecraft] high-power tuner OK Guys, I have a Physics Degree too, but realistically, if the tuner uses real coils and air capacitors like the Matchbox it is really efficient. If it uses link coupling like we did in olden days it is probably a scotch (technical term meaning a little bit) better than the more common T network. If it uses toroids, small fixed capacitors and relay switching, it probably has even more loss. So, maybe the answer is to buy a tuner that is the same size as your amplifier. If you elect to run a KTA-500 you probably are not terribly concerned whether you get 475 watts to the antenna or 450 watts. If you need an Alpha 9500 to be sure that you get through then you need the Alpha 4040 so it will look great near your 9500 and the 3 grand price will seem cheap after paying 8 grand for the amp. You can always brag on your 75 meter net that of the 1499.9 watts out of the 9500 1499.8 watts get through the 4040 to melt the RG8X that feeds your Buddy Pole. But, if the KTA-500 is your thing then a tuner that costs more than your amp and is the biggest thing in your shack (unless you have a left over BC-610) will look pretty silly. If you must measure your temperatures to figure your efficiency down to the milliwatt, be sure and use RTDs for measurement because thermocouples are not nearly accurate enough for precision measurements. 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:Elecraft@mailman.qth.net
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