RE: [Elecraft] KAT100 with Ladder Line
OK, I know this thread is over two weeks old, but I have to chime in. I have two of the 275 watt Johnson Matchboxes. One needs repairing right now. I think the 80 meter switching is defective. I borrowed an idea from a review on eham.net. The Matchbox doesn't do well with low impedances. The reviewer said to use a toriodal Un-Un to step down the impedance. And it works! A toroid at the input doesn't suffer from the disadvantages that the toroid on the output as a balun does. It will always see a non-reactive load when you tune the Matchbox. The only real downside is the extra gadget hanging off of the Matchbox with coax leads. Another idea is to move the tap on the input link closer to the grounded end. I moved it down a couple of turns. My delta loop with balanced feeders, wouldn't tune on 80 without the Un-Un mentioned above. Moving the tap down a couple of turns did trick. It is too bad the link coupled tuners aren't made anymore. Yes MFJ makes the 974H. I have it and it does match well on all frequencies. But the small knobs are touching to work it on some loads. Also the review in 9/2004 QST showed to 974H not to be as efficient on the lower bands on lower impedances. The Matchbox showed real high efficiency. The Un-Un might reduce the efficiency a little, but it is way better than an output balun. Moving the input coil tap is probably the most efficient of all. I hope this info helps some of those how have a Matchbox, but are frustrated by the limited tuning range. 73, Steve N6VL K2 #2289 -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Goody K3NG Sent: Thursday, November 15, 2007 11:00 AM To: Elecraft List Subject: Re: [Elecraft] KAT100 with Ladder Line Using any balun with an unbalanced tuner to feed balanced line can be bad news (your mileage may vary, standard disclaimers apply). Under highly reactive loads, a balun used like this can become quite lossy. There's a couple articles in publications and on the Internet on this, but Cebik's article is one that comes to mind ( http://www.cebik.com/link/l-bal.html ). It's better to run a real balanced tuner like a Johnson Matchbox, the MFJ Balanced Line tuner, or others, if you can. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] KAT100 with Ladder Line
It can be quite tedious to build one's own ladder line. Wire size and spacing between wires is a critical factor in determining the resulting impedance of the line. Maintaining consistent spacing between wires is difficult. All of this is quite true. But let me play devil's advocate. I maintain that keeping a constant impedance (and hence spacing) is not at all important. The impedance of the line could vary over a wide range (200 to 600 ohms, to pick some numbers) along the length of the line and the most important characteristics would still be conserved. 1) The line would still be low loss. 2) At any given point along the line current balance would still be maintained, even if the spacing was different than at another point. Most of us do NOT depend on the characteristic impedance of the ladder line to do an exact impedance transformation from the antenna to the rig. Rather, we use a tuning network at the transmitter end of the ladder line to do the needed impedance transformation. All a variable spacing on the ladder line means, in pragmatic terms, is a slightly different setting of the antenna tuner. I've built only one ladder line recently and the construction technique resulted in perhaps a +/- 20% variance in the spacing along the line. It works just fine. 73 ... Craig AC0DS ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] KAT100 with Ladder Line
I have not seen it mentioned yet, but the best installation of open wire line will tension the conductors between 2 supports. That means fewer spacers are required because the tensioned wires do not sway as much in the wind. For my part, PVC spacers are easy to construct and inexpensive. 73, Don W3FPR Joe-aa4nn wrote: It can be quite tedious to build one's own ladder line. Wire size and spacing between wires is a critical factor in determining the resulting impedance of the line. Maintaining consistent spacing between wires is difficult. For closely spaced wires (eg. 1.5 to 2.0 inch for 450 ohm) slight variations in spacing is very critical to maintaining consistent impedance; whereas for 6 inch spacing there is less effect on impedance with slight variations in spacing. Eg. 6 inch spacing using #12 wire will give approximately 600 ohm open wire feeders. More info at: http://www.cebik.com/trans/par.html http://www.cebik.com/gup/gup31.html I find lexan difficult to cut due to the low melting point and clogged saw teeth. Plexiglass is a little bit better. I would opt for the smallest PVC pipe, cut into 6.5 inch lengths. Cut a 1/4 inch depth notch in either end wide enough to accept #12 wire. Use a band saw, scroll saw or hand held saber saw. After inserting the wire in the PVC, put a dab of Marine Glue and Sealant on there, or other quick drying adhesive. de Joe, aa4nn ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] KAT100 with Ladder Line
Curt, There seems to be a misconception among hams that when using 450 ladder line, a 4:1 balun is the best thing to use. While that may be true in some cases, in many other cases, a 1:1 balun will serve better. It all depends on the feedpoint impedance of the feedline at the shack end, and that has little relationship with the fact that 450 ohm line is being used - i.e. the feedpoint impedance is *not* the characteristic impedance of the transmission line in most cases. The feedpoint impedance looking into the shack end of a multiband antenna can vary from extremely low to extremely high - it all depends on the length of the antenna and the length of the feedline. That being said, I would suggest that you use an Elecraft BL2 right at the output of the KAT100. Try it at the 1:1 setting first, and then try the 4:1 setting to see which produces the better results for each band. It would be informative to measure the impedance into the unbalanced end of the balun with an antenna analyzer on each band - use the setting that does not produce an extremely low of extremely high SWR on the analyzer. Often adding or subtracting a length of feedline will bring the feedpoint impedance into a better range for matching. 73, Don W3FPR Curt Milton wrote: I admit I enjoyed using a KAT100 at FD, but I wonder how much value it would be at my station. For feeding my wire antenna with balanced line, I suspect I need an external balun, that has to go someplace, and better to be attached to one of the tuner inputs. Currently I use a manual MFJ tuner (with its internal 4:1 balun) to operate my wire antenna on 30, 40, 80 and 160m. I can imagine the autotuner being useful here, but I can't envision the balun to use and how to attach it to the KAT100. My other antennas are 2 multiband verticals (80/40 and 20/17/15/12/10), and these are nicely matched where I operate - so not much utility for the KAT100 here. So will a KAT100 make my QSY more seamless, and what balun to use and how to integrate it ? ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] KAT100 with Ladder Line
For Field Day this year I had my K2 hooked up to a 130' dipole fed by ladder line. We ran that to a 4:1 balun and a few feet of coax to the KAT100. It tuned it up nicely on all bands. We had no trouble working anyone we called. Craig NZ0R -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Curt Milton Sent: Thursday, November 15, 2007 11:50 AM To: Elecraft@mailman.qth.net Subject: [Elecraft] KAT100 with Ladder Line I admit I enjoyed using a KAT100 at FD, but I wonder how much value it would be at my station. For feeding my wire antenna with balanced line, I suspect I need an external balun, that has to go someplace, and better to be attached to one of the tuner inputs. Currently I use a manual MFJ tuner (with its internal 4:1 balun) to operate my wire antenna on 30, 40, 80 and 160m. I can imagine the autotuner being useful here, but I can't envision the balun to use and how to attach it to the KAT100. My other antennas are 2 multiband verticals (80/40 and 20/17/15/12/10), and these are nicely matched where I operate - so not much utility for the KAT100 here. So will a KAT100 make my QSY more seamless, and what balun to use and how to integrate it ? 73, curt Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] KAT100 with Ladder Line
Using any balun with an unbalanced tuner to feed balanced line can be bad news (your mileage may vary, standard disclaimers apply). Under highly reactive loads, a balun used like this can become quite lossy. There's a couple articles in publications and on the Internet on this, but Cebik's article is one that comes to mind ( http://www.cebik.com/link/l-bal.html ). It's better to run a real balanced tuner like a Johnson Matchbox, the MFJ Balanced Line tuner, or others, if you can. Don Wilhelm wrote: Curt, There seems to be a misconception among hams that when using 450 ladder line, a 4:1 balun is the best thing to use. While that may be true in some cases, in many other cases, a 1:1 balun will serve better. It all depends on the feedpoint impedance of the feedline at the shack end, and that has little relationship with the fact that 450 ohm line is being used - i.e. the feedpoint impedance is *not* the characteristic impedance of the transmission line in most cases. The feedpoint impedance looking into the shack end of a multiband antenna can vary from extremely low to extremely high - it all depends on the length of the antenna and the length of the feedline. -- Blog: http://thek3ngreport.blogspot.com/ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] KAT100 with Ladder Line
On Thursday, November 15, 2007 at 7:00 PM, Goody K3NG wrote: Using any balun with an unbalanced tuner to feed balanced line can be bad news (your mileage may vary, standard disclaimers apply). Under highly reactive loads, a balun used like this can become quite lossy. There's a couple articles in publications and on the Internet on this, but Cebik's article is one that comes to mind ( http://www.cebik.com/link/l-bal.html ). It's better to run a real balanced tuner like a Johnson Matchbox, the MFJ Balanced Line tuner, or others, if you can. - Well put Sir! As a comment to the List, the usual type of cored current balun presented with a reactive load might appear not to be introducing loss because QSOs can be made, but as the members of our QRP fraternity well know contacts both 'local' and DX can be made using very low power given the right propagation conditions. Proof of this loss can be had by increasing Tx power up to the power rating of the balun at which point the balun could well explode if it has not already at a lower power, it will certainly becomes hot to touch. As K3NG says your mileage might vary because the antenna's feedpoint impedance as transformed by your feeder and seen by the balun might by happy fluke be non-reactive, feeder length and feeder impedance are factors, leaving only the R to deal with. If R turns out to be 200 ohms, then a 1:4 balun would work well with a Tx which wants to see a load of 50 +j0. FWIW I agree with K3NG that the classic balanced tuner such as used in the Matchbox is the best system to use when feeding a balanced line, good efficiency and versatile. 73, Geoff GM4ESD ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] KAT100 with Ladder Line
You are quite correct. My favorite tuner of all is a link coupled balanced tuner, and it is L B Cebik's favorite too - low loss and can be configured to match just about anything - series tuning for low impedances or parallel for higher impedances. I have built many over the years. No balun required anywhere. If I were able to bring ladderline into the shack, I would have one of my old balanced tuners with the plug-in coils to match the transmitter to the ladderline - but I can't do that (don't ask!), so I use resonant antennas fed with coax and clean up any required additional tuning with a KAT100. But, one must admit that the KAT100 does offer a lot of convenience to the operator, even though it has some drawbacks - it is not balanced, and for those who are fortunate enough to bring ladderline into the shack, it can be used with a balun. It is a workable solution as long as some cautions are observed to minimize the loss. One cannot defeat the laws of physics, but for those who must use an unbalanced tuner and a ladderline fed multiband antenna, the KAT100 followed by a balun may be an acceptable solution. Adjust the feedline length so as to provide a decent feedpoint impedance at the balun without a lot of reactance, and use a current type balun (a voltage balun just will not work well in this application), and one can get on the air - it certainly is better than no antenna at all. 73, Don W3FPR Goody K3NG wrote: Using any balun with an unbalanced tuner to feed balanced line can be bad news (your mileage may vary, standard disclaimers apply). Under highly reactive loads, a balun used like this can become quite lossy. There's a couple articles in publications and on the Internet on this, but Cebik's article is one that comes to mind ( http://www.cebik.com/link/l-bal.html ). It's better to run a real balanced tuner like a Johnson Matchbox, the MFJ Balanced Line tuner, or others, if you can. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] KAT100 with Ladder Line
I've been using Cecil Moore's (W6RCA) No-Tuner with 450 ohm ladder line for about 7 years along with a K2 / KAT-2 and it has been a pleasure to use and pretty effective. It's basically a box of 5 4pdt relays out in the yard that switches in/out combinations of 16, 8, 4, 2 and 1 foot lengths of 450 ohm ladder line to the main 450 ohm feedline to get a close match in the shack, and the KAT2 does the rest. The input to the relay box is fed with RG8X with a bead balun on the coax right at the box input. The idea is to switch just enough extra line in to get a current antinode at the antenna feedpoint for the frequency of operation. For a 80 meter half wave antenna (with 10 meter fan element tacked on), the main 450 ohm feedline is about 85-90 feet long. I've worked/confirmed ~140 countries using this antenna with 12 watts or less (mostly 5 watts). And I'm not much of a dx fanatic. 73, Lenny W2BVH Geoffrey Mackenzie-Kennedy wrote: On Thursday, November 15, 2007 at 7:00 PM, Goody K3NG wrote: Using any balun with an unbalanced tuner to feed balanced line can be bad news (your mileage may vary, standard disclaimers apply). Under highly reactive loads, a balun used like this can become quite lossy. There's a couple articles in publications and on the Internet on this, but Cebik's article is one that comes to mind ( http://www.cebik.com/link/l-bal.html ). It's better to run a real balanced tuner like a Johnson Matchbox, the MFJ Balanced Line tuner, or others, if you can. - Well put Sir! As a comment to the List, the usual type of cored current balun presented with a reactive load might appear not to be introducing loss because QSOs can be made, but as the members of our QRP fraternity well know contacts both 'local' and DX can be made using very low power given the right propagation conditions. Proof of this loss can be had by increasing Tx power up to the power rating of the balun at which point the balun could well explode if it has not already at a lower power, it will certainly becomes hot to touch. As K3NG says your mileage might vary because the antenna's feedpoint impedance as transformed by your feeder and seen by the balun might by happy fluke be non-reactive, feeder length and feeder impedance are factors, leaving only the R to deal with. If R turns out to be 200 ohms, then a 1:4 balun would work well with a Tx which wants to see a load of 50 +j0. FWIW I agree with K3NG that the classic balanced tuner such as used in the Matchbox is the best system to use when feeding a balanced line, good efficiency and versatile. 73, Geoff GM4ESD ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] KAT100 with Ladder Line
I've been very pleased with my MFJ-974, a true balanced tuner. My measurements of feedline current with RF ammeters indicate that overall it is as efficient as my home brew link coupled tuner with plug in coils. I've used the MFJ tuner with several combinations of feedline lengths and radiator lengths, and I've never failed to get a perfect match on all bands from 80 m to 10 m. I'd like also to mention that Dipole3.exe is an excellent, free, and very easy to use program for modeling a dipole fed with balanced line. You can play with different values of feedline length and radiator length, as well as many other parameters, to determine efficiency and impedance at the transmitter end of the feedline. One source of Dipole3.exe is http://www.smeter.net/software/dipole3.exe . Dick, K0KK On Nov 15, 2007, at 1:00 , Goody K3NG wrote: vf Using any balun with an unbalanced tuner to feed balanced line can be bad news (your mileage may vary, standard disclaimers apply). Under highly reactive loads, a balun used like this can become quite lossy. There's a couple articles in publications and on the Internet on this, but Cebik's article is one that comes to mind ( http://www.cebik.com/link/l-bal.html ). It's better to run a real balanced tuner like a Johnson Matchbox, the MFJ Balanced Line tuner, or others, if you can. Don Wilhelm wrote: Curt, There seems to be a misconception among hams that when using 450 ladder line, a 4:1 balun is the best thing to use. While that may be true in some cases, in many other cases, a 1:1 balun will serve better. It all depends on the feedpoint impedance of the feedline at the shack end, and that has little relationship with the fact that 450 ohm line is being used - i.e. the feedpoint impedance is *not* the characteristic impedance of the transmission line in most cases. The feedpoint impedance looking into the shack end of a multiband antenna can vary from extremely low to extremely high - it all depends on the length of the antenna and the length of the feedline. -- Blog: http://thek3ngreport.blogspot.com/ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
