See http://n4xm.myiglou.com--click on the blue ribbon for sure.
I am a licensed professional electrical engineer and have a US Patent for my unique tuner. I have been an active ham for decades. Belive what and who you want, or seek the truth. I don't debate on the internet. 73 Paul N4XM At 11:42 AM 10/16/2013 -0600, you wrote: >As Tom notes, the widest possible matching range for a T-Network is with two >adjustable capacitors (and, presumably, a variable inductor, typically a >roller inductor). Constraining any one of these parameters reduces the >available matching range. Further, Tom correctly observes that many hams >damage their tuners by unwisely choosing a combination of C and L that >dissipates much of their transmitted RF in the tuner itself. > >Several years ago, I wrote a three-part series of articles for QST about a >high-power homebrew T-match autotuner. Part I of the series (QST, April >2002, p.40) shows two graphs (Figures 2 and 3) that give the range of >adjustment values for Cin, Cout, and L for a T-match network, using the 160m >band as an illustration. The first graph (Fig.2) shows the values of Cin and >Cout (for different values of L) required to match resistive loads from >3-800 ohms. The second graph (Fig.3) is the more interesting one for this >discussion, however, because it shows the percentage power loss in the >T-network for different values of L. > >Here is the key point: With a T-network, the lowest power dissipation occurs >with the smallest value of L that will give a match. To illustrate the >importance of this rule of thumb, suppose one is matching a 6.25 ohm >feedline (8:1 VSWR) at 1.8 MHz. According to the graph, the largest >practical nductance that can match this load is about 25 uH, while the >smallest practical inductance is about 2 uH. Although each inductance will >give a satisfactory 1:1 match (assuming Cin and Cout are properly chosen), >the 25 uH choice dissipates nearly 40% of the transmit power in the tuner, >which is about 600W at the legal limit. Goodbye tuner! On the other hand, >the 2 uH choice dissipates only about 45W. (Note that these values are only >for resistive loads, but they illustrate the general principle.) > >There is a tradeoff, unfortunately, in using the smallest possible value of >inductance to match a given feedline, and that is that large values of Cin >and Cout are required. For this example, using a 2 uH inductance requires >Cin and Cout to be greater than 1000 pF. With a 25 uH inductance, Cin and >Cout only need to be about 100 pF. The problem is that designers of >commercial and homebrew T-network tuners sometimes skimp on the capacitance >range available, instead opting for larger (and cheaper) inductors. Buyers >are initially pleased at the low cost and wide matching range of their >spiffy new tuner, only to discover later that the tuner destroys itself when >they turn on their amplifier. And, as Tom notes, the problem is compounded >if they tune their T-networks incorrectly by following the wrong rule of >thumb! > >73, >Jim W8ZR > >> -----Original Message----- > >> Subject: Re: Topband: W8ji ATR-10 design 160M? >> >> Respectfully, the X match is nothing but a common T-match with a fixed >> capacitor in one leg. In a normal T-match, operating Q can be varied over >a >> wide range by adjusting L/C ratios. By restricting range of one leg, >> operating Q range is limited. So it actually **is** a T match, it just has >> two adjustable branches instead of the more common three adjustable >> branches, restricting the operating Q range and matching range. >> >> The ATR10 is more like the common old Johnson matchbox, with the >exceptions >> instead of a link it has a tap and it is single ended. The tap sets the >> operating Q, just as the link ratio sets the operating Q in a Matchbox. >> This restricts the matching range and operating Q range. >> >> Tuners that fix the operating Q at a certain value, or limit the operating >Q >> range, will always restrict matching range. The operating Q restriction >> limits peak voltages or currents by preventing grossly improper >adjustments, >> but the very same thing that limits voltages or current by definition also >> limits matching range. >> >> An L network limits matching range the most of any network for a give >range >> of component values, but also limits operating Q the most. It has only one >> operating Q available at any given impedance ratio. The Q varies with load >> impedance. You cannot have too much Q, or it won't match. >> >> This is, unfortunately, the way the world works. Everything is a tradeoff >of >> matching range, cost, complexity, and power rating. No single network, >just >> like no single balun, is all things to all cases. >> >> The widest matching range for a given cost is a T network with two >> adjustable capacitors and one shunt inductor. Unfortunately, people think >> (and articles repeat) the silly idea that the proper way to tune is to >start >> with capacitors at half and tune for maximum receive. >> >> Most of any improvement centers around preventing people from doing >> something silly, by limiting what they can do. There isn't any magic >> circuit. >> >> Tom >> >> ----- Original Message ----- >> From: "N4XM Paul D. Schrader" <[email protected]> >> To: "Jim GM" <[email protected]> >> Cc: "topband" <[email protected]> >> Sent: Wednesday, October 16, 2013 11:01 AM >> Subject: Re: Topband: W8ji ATR-10 design 160M? >> >> >> > Jim, >> > >> > I did not make the comments you said I made below. And the XMATCH >Antenna >> > Tuner is NOT a "T" match. >> > It is a patented circuit. This unique circuit is a United States >Patent. >> > >> > And see http://n4xm.myiglou.com >> > >> > Paul N4XM >> >> _________________ >> Topband Reflector > >_________________ >Topband Reflector > _________________ Topband Reflector
