Just because it was published by the ARRL does not make it a good design, although it might help to sell a few.
Zack Lau published a QRP version of that tuner some years back and later retracted it, and it has not been mentioned much since, but Dean Straw published his high power version of about the same design and that seems to be the "best thing since sliced bread" despite counterclaims by noted authorities on balun and RF designs - W8JI, W7El and others. Bottom line, it just does not work well, although there will be many who will say that "Alpha makes good stuff", that still makes it a stretch of the laws of physics - using an unbalanced network "floating" (although not really isolated from a common reference (ground)) will still not make everything balanced. I know there are those who will claim that an off center fed dipole has a balanced feedpoint, but I am not convinced. I put the "balun at the input" tuners in the same category. Take a balanced signal (output of a balun) and feed it through an unbalanced network, and claim that the output of that unbalanced network is balanced just does not make much sense to me. Maybe with ideal components it *might* be possible, but if one would plot the reactance and phase delay around that unbalanced network using good scientific methods, it would become obvious that the output would not be of equal and opposite currents with 180 degrees phase difference. If the schematic does not look balanced, it is not really balanced. Follow the leading current and lagging current around the circuit to convince yourself. 73, Don W3FPR On 11/26/2011 10:10 PM, David Gilbert wrote: > If I remember correctly, the announcement for the Alpha tuner even > stated that they "drew heavily" (or words to that effect) from the ARRL > Antenna Book for the design. > > 73, > Dave AB7E > > > > On 11/26/2011 6:37 PM, Paul Christensen wrote: >>> I was surprised to see this from Alpha, whom I would have expected to know >>> better. >> The identical design (less automated functions) can seen in recent issues of >> the ARRL Antenna Book For example, see 20th Ed., pp. 25/15 - 25/19 and >> titled "High-Power ARRL Antenna Tuner for Balanced or Unbalanced Lines." >> Even output C is the same at 800 pF max. >> >> Paul, W9AC >> >> __ > ______________________________________________________________ > 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
