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 At 12:56 PM 10/8/2013 -0500, you wrote: >Tom W8JI made some measurements back in 1997 on the ATR-15 when it first >came out. Not sure how this will print out. > >* >* > >*The ATR-15 measures as follows for load R and loss on 1.8 MHz: >12.5 ohms 21.8% (27.8%) >25 ohms 16.5% (22.9) >50 ohms 10.6% (11.0) >100 ohms 8.9% (10.7) >200 ohms 8.1% (10.4) >400 ohms 7.4% (10.1) >800 ohms 6.9% (8.8%)* > > >Doubling the value of C cuts low impedance losses in half. I put 500 pF >air variable caps in the ATR-15 and the 12.5 ohm loss was 13.1 percent. > >I don't even come close to the MFJ-989 results they published. I >measured the values (they are the ones in brackets above) for the 989 >using both an HP 4191A analyzer and a Harris RF voltmeter, as well as >confirmed on meters. > > >My question is where in the tee match was the extra capacitance installed? >was it going to ground? > >N4XM commented in 1997 on the MFJ 989 review. > >>*>>T network tuners (like the 989, Xmatch, Vectronics, Tucker, * >>*>>Murch, etc) handle the least power on 160 and with capacitive* >>*>>reactance low resistance loads. T network tuners handle MORE * >>*>>power into higher resistance loads or loads with some amount * >>*>>of inductive reactance. * > > >w8JI comments > >>*L network tuners (like the Ten-Tec, Nye Viking, etc) handle more* >>*power into impedances near 50 ohms, but often do a poor job * >>*matching reactive or very low impedance loads on low frequencies. (Sometimes* >>*these tuners are called Pi-networks, even though* >>*they do not really function as a pi except perhaps on 15 or ten* >>*meters) * >>** >>*In a T network tuner, maximum efficiency and power handling * >>*generally occurs when maximum and equal amounts of * >>*capacitance are used in the capacitors, and the least amount of* >>*inductance is used. This is true even though many other settings* >>*will produce a low SWR.* > > > >I later read more archives. What came up was the ATR-30 How beefy it was. > What the plate spacing on this tuners capacitors? I would think on a >short antenna like mine it is not enough. > >So back to the ATR-10. The W8JI design with variable taps seams to handle >high power with nor arcing problems. > I just do not know why this is working for me. Can some one please explain >this to me I am confused? All this reading >requires a younger mind. > >Jim K9TF > >On Sat, Oct 5, 2013 at 1:54 PM, Jim GM <jim.gmfo...@gmail.com> wrote: > >> >> My antenna is a 99 foot inverted L for 160M with 95 short radials 2000 >> feet of wire. >> >> What I am trying now is W8JI suggested modification design to improve the >> ATR-10 design by taps on the coil for adjustment. Works well. >> http://www.w8ji.com/antenna_tuners.htm >> >> Had my MFJ-989B at the feed point, I had to add a capacitor to ground >> 250pf so it could work. Inductance was at max farthest away from ground. >> Voltage was so high at 300 watts in, the 0.125 meshed plate spacing arced >> over, it has a T network and I had expected this to happen. >> http://www.mfjenterprises.com/support/MFJ-989B/MFJ-989B.pdf I run 500 >> watts. >> >> What I was looking at is removing the coil and the input would be at the >> top of C1. I made a test with QRP using 2 small spaced caps taken out of an >> MFJ-901A. Works well. Because of the high voltage situation would there be >> an issue with this and I need to go to a 0.25 inch spacing between plates? >> Vacuum variables are out of my price range. >> >> ATR-10 with W8JI modifications is a high pass tuner or is it? Removal of >> the coil would make this a low pass circuit. Besides that on 160M which one >> would be more efficient, and off the top of your head what would be the >> percentages? If you had my make do with what I have setup, what tuning >> network would you use? >> >> Does any one have an email address for MFJ Service department? I have the >> wrong one. I sent my MFJ 998RT to their Service department, the High >> voltage that was developed with 300 watts pretty much done it in. The >> ATR-10 W8JI redesign has greatly reduce the High voltage that I was seeing >> with out the inductor. >> >> -- >> Jim K9TF >> > > > >-- >Jim K9TF >_________________ >Topband Reflector > _________________ Topband Reflector