A T-Network tuner with a large enough capacitor in one leg set to full capacity is essentially an L-network tuner.
73, Dave AB7E On 3/9/2012 9:55 PM, Don Wilhelm wrote: > Mike and all, > > The T-Network tuners are problematic even though they can be quite > wide-range - they may show multiple tuning condition for any given > antenna/matching situation. They should always be adjusted for the > largest value of capacity that will tune properly. > > Most automatic tuners are of the L network type which avoids the > ambiguous tuning spots of the T-network tuners. > > 73, > Don W3FPR > > On 3/9/2012 10:22 PM, Mike WA8BXN wrote: >> 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:[email protected] >> >> 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:[email protected] > > 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:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
