The N2SMH "Z-Match" Project Thread
Has anyone built W6JJZ's updated Z-match tuner (QRP Quarterly, July 1995, page 10)? I've been wanting to build a balanced-line tuner for field use and this looks promising. So I'm looking for any feedback from the assembled multitudes. Does anyone know if Charlie's take on the Z-match is different than Emtech's?
Oh yeah...anyone have a source for T-200-6, T-130-6 or T-157-6 cores?
Glen Rock, NJ
Danny K3TKS responds:
I think that they are very close, but a note to Roy Gregson, W6EMT will get you the straight scoop in short order. More pictures and discussion on the subject can be found in Chapter 7 of the New Antenna Handbook by William I. Orr, W6SAI (ISBN 0-943016-15-0) available for $ 19.95 at your favorite Ham Radio Book Dealers. I wrote a few notes about it in the July 1997 issue of the QRP Quarterly Journal. IMHO, it is the best antenna book out there for the new ham on the block. I recommend it to all as a worthy addition to their Antenna Library Collection.
No, I don't get any thing for saying that, Bill dosen't even know me :^) And yes, I paid full price for my copy at my Favorite Ham Radio Candy store, Maryland Radio Center, in Laurel, MD <http://www.weathernode.com>
We should have some local QRP Photos on that system soon. /QRP.html
email to Roy at <RoyGregson@aol.com>
Q: "What are you using for caps? (I have a couple of dual 365pF air variables from James Bennett, although at 2"x2"x1.5" the case may need to be bigger than I hoped.) Also, did you find a source of the toroids?"
A: I'm still waiting on an enclosure that I ordered from TechAmerica. Maybe it'll show up by tomorrow. Can't do too much without it. This project is more about drilling holes than anything else.
James's caps are exactly what I'm using. I think they're perfect for it. Charlie's article called for a minimum of 330 pF per section and these measure 500 pF per section and up on the Autek at 7 MHz. I got my T-200-6 core from Debco in Cincinnati, although you can get one from Amidon or Palomar directly. Actually, Amidon is probably a little less money. I just happened to have a Debco flier in my office. And just today I got my hands on some #18 enamel wire for the big main coil. So aside from the box, I'm all set.
Size isn't an issue for me, really. I'm not a backpacker/camper and although I intend this Z-match primarily for portable use, it won't matter much to me if it's a little heavier and/or larger. The case I ordered is about 4 x 5 x 6 or 7 inches. It'll be a bit roomy in there, but that's OK. I'll have room to add an SWR bridge should the urge come over me on some cold, dead-band winter day.
I've had e-mail dialogue with both Charlie, W6JJZ and Fred Bonavita, W5QJM, who's quite a fan of the Z-match. You can see Fred's version in the Jan. 1996 Quarterly, by the way. Both of them told me that I'd get best results by not trying to build the smallest possible Z-match for portable use.
Efficiency is likely to suffer if you go that way. Fred, in particular, advised me to use the bigger toroid and heavy wire for the winding. Charlie said that the core I'm using will easily handle 100 W at HF. He said that overall, the limiting factor for power handling in the tuner will be the spacing between the capacitor plates. All well and good, but I plan QRP use only (don't have a QRO rig unless you count the Scout). It's nice to know, though, that your tuner can take some punishment if need be.
Sure, I'd love to contribute to the Members' Section. I'll try writing something up after I find out if it works! The schematic is in the July 95 QRP Quarterly. Is it better to take regular photos or to have one of the guys with a digital camera take them at the next get-together (assuming I have it done by then)?
My [enclosure] is going to be kind of grunge, I think. I'm probably not going to bother painting this time. So it'll be au naturel aluminum finish. I got going yesterday with it and actually almost got it finished. I have just the last bit of wiring to do. I still haven't figured out how to mechanically fixture the toroid. If you have any good ideas, by all means pass them along. It's a BIG core, biggest I've ever worked with by far. A T-37-2 it ain't.
What I did do was to steal Fred Bonavita's idea of kinda sorta mounting the core on perfboard. He threaded the coil leads through the board to hold them in place and then somehow affixed the perfboard to the rear of the frames of the variable caps. That's at least what it looks like he did in the Jan. 96 QRP Quarterly piece he did with pictures.
For sure...a Sierra case would be ideal. I briefly entertained the idea of calling Bob Dyer to see whether he'd sell a blank case. The very idea of the cost, which I'm sure would be pretty high, was enough to stop me. But it's the perfect size. If you're using James's caps, as I am, you must have at least 2.5 in. of interior height. At some point in the middle of their range, the rotor plates rise to a height of roughly 2-1/8 in. I had to add another eighth of an inch because I used nylon nuts as spacers to insulate the frames from the case. Well, I'm sure you'll take the measurements and do the math.
I'm building this real minimalist to start. It'll have balanced output only to start. I figure I can add coax output later. A work in progress, if you will.
(Dave will be publishing more details on his Z-Match soon.)