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
