Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
Many thanks, gentlemen, for the many words of wisdom. The topic, so far as I am concerned at least, is now closed! 73 Stephen G4SJP __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
Don, So you want to add +j1000 to +j1000 to get zero? Wes --- On Sun, 1/2/11, Don Wilhelm w3...@embarqmail.com wrote: Wes, I don't know about the -j501, but Kirchoff tells me that a series Xl = j1000 alone will cancel the +j1000 in the shack feedpoint (your example) leaving a 50 ohms pure resistive load, no need for the shunt element. Since the absolute value of the Low Pass L-net impedance requires that Rl be less than Rs, I do not know how a Low Pass section would provide a match. The matching section must be a High Pass with your values. 73, Don W3FPR On 1/2/2011 10:22 PM, Wes Stewart wrote: Sort of sounds logical but it's wrong. Let the load in the shack be 50 +j1000. A low-pass L-net with a shunt Xc = -j501 and series Xl = j1000 will do it. Wes N7WS --- On Sun, 1/2/11, Don Wilhelmw3...@embarqmail.com wrote: As you mentioned, the matching range of the KAT3 becomes greater as the frequency is increased. That fact is often overlooked by many hams. It is all about the amount of L and C available in the tuner, but the inductive or capacitive reactance is really what counts in producing the match. If the feedpoint in the shack has 1000 ohms of inductive reactance, and the tuner has only 600 ohms capacitive reactance to attempt to cancel that inductance, then a match will never happen. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
Wes, It was late last night and I misinterpreted the sign - so yes, that was what my eyes at that time did to me. Your solution is more correct in the light of day. 73, Don W3FPR On 1/3/2011 9:06 PM, Wes Stewart wrote: Don, So you want to add +j1000 to +j1000 to get zero? Wes --- On Sun, 1/2/11, Don Wilhelmw3...@embarqmail.com wrote: Wes, I don't know about the -j501, but Kirchoff tells me that a series Xl = j1000 alone will cancel the +j1000 in the shack feedpoint (your example) leaving a 50 ohms pure resistive load, no need for the shunt element. Since the absolute value of the Low Pass L-net impedance requires that Rl be less than Rs, I do not know how a Low Pass section would provide a match. The matching section must be a High Pass with your values. 73, Don W3FPR On 1/2/2011 10:22 PM, Wes Stewart wrote: Sort of sounds logical but it's wrong. Let the load in the shack be 50 +j1000. A low-pass L-net with a shunt Xc = -j501 and series Xl = j1000 will do it. Wes N7WS --- On Sun, 1/2/11, Don Wilhelmw3...@embarqmail.com wrote: As you mentioned, the matching range of the KAT3 becomes greater as the frequency is increased. That fact is often overlooked by many hams. It is all about the amount of L and C available in the tuner, but the inductive or capacitive reactance is really what counts in producing the match. If the feedpoint in the shack has 1000 ohms of inductive reactance, and the tuner has only 600 ohms capacitive reactance to attempt to cancel that inductance, then a match will never happen. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
[Elecraft] [K3] KAT3 and 160 with 40m long doublet
I have only just recently added the KAT3 and I'm very impressed with it, but given the praise heaped upon it by others I'm slightly surprised that the best VSWR I can get on 160m is about 8:1. The antenna is approximately a doublet which is a half wave long on 80m I say 'approximately' as it's slightly off-centre fed. I have about 7m of 300 ohm slotted down from the feedpoint and then into a coaxial choke at roof level for the remaining 10m into the back of the K3. Substituting the straight connection for a 4:1 balun (Guanella) at the transition between the slotted feeder and the coax helps slightly but not by much. Unfortunately I don't have a vector analyser, so I have no idea of the nature of the reactance that the K3 is seeing. However, given the wavelength involved, I would need to add a very significant length of coaxial cable if I were to swing the point around the Smith Chart. I have tried to manually tune the KAT3, but unless I am missing something, I am am not able to change the L and C values at the same time as transmitting, so it's a very tedious process. Tomorrow I may well add some extra wire to hang vertically down from the ends of the doublet. In the meantime I would be pleased to hear any comments. Happy New Year! 73 Stephen, G4SJP __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
Stephen, What is the SWR without the tuner ? 73 Ken K5DNL -- --- On Sun, 1/2/11, Stephen Prior s...@sjprior.fsnet.co.uk wrote: From: Stephen Prior s...@sjprior.fsnet.co.uk Subject: [Elecraft] [K3] KAT3 and 160 with 40m long doublet To: elecraft elecraft@mailman.qth.net Date: Sunday, January 2, 2011, 1:31 PM I have only just recently added the KAT3 and I'm very impressed with it, but given the praise heaped upon it by others I'm slightly surprised that the best VSWR I can get on 160m is about 8:1. The antenna is approximately a doublet which is a half wave long on 80m I say 'approximately' as it's slightly off-centre fed. I have about 7m of 300 ohm slotted down from the feedpoint and then into a coaxial choke at roof level for the remaining 10m into the back of the K3. Substituting the straight connection for a 4:1 balun (Guanella) at the transition between the slotted feeder and the coax helps slightly but not by much. Unfortunately I don't have a vector analyser, so I have no idea of the nature of the reactance that the K3 is seeing. However, given the wavelength involved, I would need to add a very significant length of coaxial cable if I were to swing the point around the Smith Chart. I have tried to manually tune the KAT3, but unless I am missing something, I am am not able to change the L and C values at the same time as transmitting, so it's a very tedious process. Tomorrow I may well add some extra wire to hang vertically down from the ends of the doublet. In the meantime I would be pleased to hear any comments. Happy New Year! 73 Stephen, G4SJP __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
That is a really tough antenna to match for 160 Stephen. The classic way to use an 80 meter dipole on 160 is to short the feed line at a ground point and feed it with the center conductor with the braid to the best counter poise you can manage. This will make you a T topped Marconi which will probably tune for you. Willis 'Cookie' Cooke K5EWJ From: Stephen Prior s...@sjprior.fsnet.co.uk To: elecraft elecraft@mailman.qth.net Sent: Sun, January 2, 2011 1:31:06 PM Subject: [Elecraft] [K3] KAT3 and 160 with 40m long doublet I have only just recently added the KAT3 and I'm very impressed with it, but given the praise heaped upon it by others I'm slightly surprised that the best VSWR I can get on 160m is about 8:1. The antenna is approximately a doublet which is a half wave long on 80m I say 'approximately' as it's slightly off-centre fed. I have about 7m of 300 ohm slotted down from the feedpoint and then into a coaxial choke at roof level for the remaining 10m into the back of the K3. Substituting the straight connection for a 4:1 balun (Guanella) at the transition between the slotted feeder and the coax helps slightly but not by much. Unfortunately I don't have a vector analyser, so I have no idea of the nature of the reactance that the K3 is seeing. However, given the wavelength involved, I would need to add a very significant length of coaxial cable if I were to swing the point around the Smith Chart. I have tried to manually tune the KAT3, but unless I am missing something, I am am not able to change the L and C values at the same time as transmitting, so it's a very tedious process. Tomorrow I may well add some extra wire to hang vertically down from the ends of the doublet. In the meantime I would be pleased to hear any comments. Happy New Year! 73 Stephen, G4SJP __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
On 1/2/2011 11:31 AM, Stephen Prior wrote: In the meantime I would be pleased to hear any comments. The condition you describe is not at all surprising for an antenna that's half the length it needs to be for an acceptable match. 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
I guess I feel rather foolish. Why I should have expected the KAT3 to cope I don't know, perhaps I have been swayed by the reports of others who have claimed that the KAT3 would load anything anywhere! I shall have to lengthen the antenna. I don't have a good enough ground to feed the antenna as a Marconi so my options other than lengthening the antenna are rather limited. I'm not limited by space so much as by a very convenient distance between two tall trees! 73 Stephen G4SJP Let us consider the topic closed! On 02/01/2011 19:51, Jim Brown j...@audiosystemsgroup.com wrote: On 1/2/2011 11:31 AM, Stephen Prior wrote: In the meantime I would be pleased to hear any comments. The condition you describe is not at all surprising for an antenna that's half the length it needs to be for an acceptable match. 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
I used a low and bent doublet of 2 x 88ft per section for a while and it tuned up amazingly well on all bands 160 to 10 with the KAT3. As a rule I like to use multi-band doublets away from any obvious in-band resonances, so that it doesn't experience very high Z anywhere, so, adding a bit on each end and stringing them wherever they will sensibly go should work for you. A choke in the coax feed is good. David G3UNA I have only just recently added the KAT3 and I'm very impressed with it, but given the praise heaped upon it by others I'm slightly surprised that the best VSWR I can get on 160m is about 8:1. The antenna is approximately a doublet which is a half wave long on 80m I say 'approximately' as it's slightly off-centre fed. I have about 7m of 300 ohm slotted down from the feedpoint and then into a coaxial choke at roof level for the remaining 10m into the back of the K3. Substituting the straight connection for a 4:1 balun (Guanella) at the transition between the slotted feeder and the coax helps slightly but not by much. Tomorrow I may well add some extra wire to hang vertically down from the ends of the doublet. In the meantime I would be pleased to hear any comments. Happy New Year! 73 Stephen, G4SJP __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
That's not correct. I use a 40.8 m long windom and it's no problem to tune to a swr abt. 1.2 with the KAT3 on the 160m band. 73 Detlef, DL7NDF Am 02.01.2011 20:51, schrieb Jim Brown: On 1/2/2011 11:31 AM, Stephen Prior wrote: In the meantime I would be pleased to hear any comments. The condition you describe is not at all surprising for an antenna that's half the length it needs to be for an acceptable match. 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
On 1/2/2011 12:03 PM, Stephen Prior wrote: I don't have a good enough ground to feed the antenna as a Marconi so my options other than lengthening the antenna are rather limited. Don't give up so easily. In Chicago, I used a big wrought iron fence plus a dozen or so 30 ft long wires as counterpoise for a Marconi; KK9H has used the HVAC ducts in his home. ANY counterpoise is better than NO counterpoise. In another installation, I've run as many fairly short wires as I could from the base of the antenna, connected them together, and to the coax shield. Was it as good as 70 quarter-wave radials? Of course not. Did the antenna work well enough for me to have a lot of fun? Yup! My Marconi was a 100 ft long center-fed dipole with loading coils to resonate it on 80M. Just for fun, I tried loading it as a dipole on 160. Performance was wretched. Using it as a Marconi gave me signal reports at least 10dB better. 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
Jim, a large iron deposit lies north and west of Chicago, so verticals work very well in many areas around Chicago. I live on the Texas Gulf Coast which is salt laden gumbo from an ancient sea and verticals work very well here. I don't know about Stephen's area of the UK, but I will easily accept his experience that verticals don't work well there. Willis 'Cookie' Cooke K5EWJ From: Jim Brown j...@audiosystemsgroup.com To: elecraft@mailman.qth.net Sent: Sun, January 2, 2011 3:42:12 PM Subject: Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet On 1/2/2011 12:03 PM, Stephen Prior wrote: I don't have a good enough ground to feed the antenna as a Marconi so my options other than lengthening the antenna are rather limited. Don't give up so easily. In Chicago, I used a big wrought iron fence plus a dozen or so 30 ft long wires as counterpoise for a Marconi; KK9H has used the HVAC ducts in his home. ANY counterpoise is better than NO counterpoise. In another installation, I've run as many fairly short wires as I could from the base of the antenna, connected them together, and to the coax shield. Was it as good as 70 quarter-wave radials? Of course not. Did the antenna work well enough for me to have a lot of fun? Yup! My Marconi was a 100 ft long center-fed dipole with loading coils to resonate it on 80M. Just for fun, I tried loading it as a dipole on 160. Performance was wretched. Using it as a Marconi gave me signal reports at least 10dB better. 73, Jim K9YC __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
On Sun, Jan 2, 2011 at 3:18 PM, Dr. Detlef Petrausch dl7...@t-online.dewrote: I use a 40.8 m long windom and it's no problem to tune to a swr abt. 1.2 with the KAT3 on the 160m band Yep, similar results here. I have used 7 different ATUs and the KAT3 is the best by far. The antenna can be way shorter than 1/2 wave and still tune up fine. No loading scheme is needed. A short antenna just presents a capacitive reactance (a -j value) to the tuner, which in my experience the KAT3 has always been able to deal with. According to my antenna analyzer, on some frequencies my antennas present reactive loads that put an SWR on the coax up to about 20:1. But I have only a short run of coax between balun and transmitter, so the loss is low. However, when the load presents a lot of reactance, I have found that it has been helpful in certain antenna setups to have a good counterpoise arrangement where the balanced feedline comes into the shack and goes into the balun. The counterpoise doesn't have to be resonant, nor does it need to be elaborate. Tony KT0NY __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
It's very patchy: there are areas of huge clay deposits stretching for miles and very deep; I've forgotten the geological term for it, but I understand it was pushed into place by the last ice age; good for low loss low angle radiation I understand. There are also large areas of sand stone which is pretty hopeless for anything radio they tell me. Looking at the geology around Stephen I'd say it wasn't too good, however the sea isn't far away so the take off to the States is quite good if the immediate area around the antenna could be made efficient. Isn't the internet wonderful? David G3UNA I don't know about Stephen's area of the UK, but I will easily accept his experience that verticals don't work well there. Willis 'Cookie' Cooke __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
The real issue with verticals over bad ground of that sort is to couple as little of it as possible. There is good evidence that DENSE elevated radials are effective over really bad earth. Since dense and elevated coupled together can easily be one of those easy-to-say-and-don't-dare-do situations practically, the possibility may make little difference. 73, Guy. On Sun, Jan 2, 2011 at 6:07 PM, David Cutter d.cut...@ntlworld.com wrote: It's very patchy: there are areas of huge clay deposits stretching for miles and very deep; I've forgotten the geological term for it, but I understand it was pushed into place by the last ice age; good for low loss low angle radiation I understand. There are also large areas of sand stone which is pretty hopeless for anything radio they tell me. Looking at the geology around Stephen I'd say it wasn't too good, however the sea isn't far away so the take off to the States is quite good if the immediate area around the antenna could be made efficient. Isn't the internet wonderful? David G3UNA I don't know about Stephen's area of the UK, but I will easily accept his experience that verticals don't work well there. Willis 'Cookie' Cooke __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
The length of the radiator is only half the story. Unless the feedline is matched to the impedance at the antenna feedpoint, there will be SWR on the transmission line. When there is SWR on the transmission line, the type of line and its length become important when comparing whether any given antenna will work the same as any other antenna of the same length. So if you do not state the type and length of your feedline, it is like comparing apples to oranges. If you do not understand this phenomenon, take a look at the Antenna, Transmission Line, Tuner article on y website www.w3fpr.com. *If* it just so happens that the KAT3 cannot tune a particular antenna, then the impedance in the shack may be very low or very high (out of the range of the tuner). Adding or subtracting a 1/8 wavelength of feedline will often bring it into range, and that is normally the easiest solution if the only thing you are considering is the ability of the tuner to produce a match. 73, Don w3FPR On 1/2/2011 5:39 PM, Tony Estep wrote: On Sun, Jan 2, 2011 at 3:18 PM, Dr. Detlef Petrauschdl7...@t-online.dewrote: I use a 40.8 m long windom and it's no problem to tune to a swr abt. 1.2 with the KAT3 on the 160m band Yep, similar results here. I have used 7 different ATUs and the KAT3 is the best by far. The antenna can be way shorter than 1/2 wave and still tune up fine. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
Even if you can tune a 40m wire on 160, that doesn't mean it will work well. In my experience, short wires for the low bands are an exercise in futility. Barry W2UP -- Barry Kutner, W2UP Lakewood, CO __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
On Jan 2, 2011, at 4:01 PM, Don Wilhelm wrote: Adding or subtracting a 1/8 wavelength of feedline will often bring it into range, and that is normally the easiest solution if the only thing you are considering is the ability of the tuner to produce a match. You can see what Don means by taking a look at this figure (KAT3 at 1.8 MHz, with Smith Chart centered at 50+i0 ohms): http://homepage.mac.com/chen/Technical/Tuner/tuner1.8.png Each point on the Smith Chart is a point that the KAT3 can be brought to an precise SWR of 1.0:1. The blue points are for the KAT3 cap on one side of the inductor and the green points are for the cap switch to the other end of the inductor (the KAT3 is an L tuner, with a relay K17, that switches the caps to one or the other side of the inductor). The center of the Smith Chart circle represents an antenna with an SWR of 1.0:1. As you go out towards the circumference, you have growing circles with the same centers, with ever increasing SWR. Notice (as Don mentioned) that when the SRW is large (towards the circumference of the Smith Chart), there are huge swaths of empty spots in the Smith Chart. These are terminations that the KAT3 can never bring to an SWR of 1.0:1. However (again, as Don mentioned), there are large areas beyond the blue region where you can rotate yourself along on a constant SWR circle and drop yourself right into where the dense green dots are! Voila, ability to tune to an SWR of 1.0:1 while you could not do so without rotating. How do you rotate yourself? A length of transmission line, of course! If you remember your transmission line theory, adding a transmission line will move you along a constant radius circle centered at SWR = 1.0:1. The 1/8 wavelength that Don mentioned will rotate you by 90 degrees. In the case of the K3, you may have to try everything up to about 3/4 of a wavelength since the green and blue parts are not symmetrical. (Yes, 3/4 wavelength at 160m is no fun :-). By the way, if you look carefully, there are SWR values outside of the blue-green Yin-Yang looking region, that are not occupied. I.e., there *will* be antennas that you will never be able to tune even if you try different transmission lines until you are blue in the face. But this plot (again, with reference center at 50 ohms) should quickly tell you which antenna is tunable at 1.8 MHz. If you want to look at the full resolution PDF of the above plot (warning: 9.4 MB), you can use this link: http://homepage.mac.com/chen/Technical/Tuner/tuner1.8.pdf The points are computed by using the capacitor and inductor values of the KAT3. The KAT-100 uses slightly different L and C -- if you are interested in seeing how that tuner works, and can run Xcode on a Mac, I am more than glad to send you the source code that you can modify to produce the PDF chart for a KAT100. The interesting thing about the KAT3 is that as you go up in frequency, the dots become sparser, but do cover the most of the Smith Chart circle out to very high SWR circles. That means that as you go up in frequency, you might not be able to tune to exactly SWR 1.0:1 but you can get close enough that it should not be a problem to tune any load well enough practically. For example, the KAT3 looks like this on 20m: http://homepage.mac.com/chen/Technical/Tuner/T14080.jpg Again, if you have Xcode loaded on your Mac (Xcode is on every Mac OS X Installer DVD, but you have to ask for it to be installed), I will be glad to send you the Xcode project so you can generate plots for any frequency that you wish. Vy 73 Chen, W7AY __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
On Jan 2, 2011, at 5:52 PM, Kok Chen wrote: You can see what Don means by taking a look at this figure (KAT3 at 1.8 MHz, with Smith Chart centered at 50+i0 ohms): http://homepage.mac.com/chen/Technical/Tuner/tuner1.8.png I should add that, if memory serves (it has been a while ago that I wrote the program), the blue and green points are what an SWR 1.0:1 is transformed to by the KAT3. An antenna that will produce a match is actually the complex conjugate of one of the blue or green points (easy to figure out on the Smith Chart). 73 Chen, W7AY __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
On Jan 2, 2011, at 5:52 PM, Kok Chen wrote: In the case of the K3, you may have to try everything up to about 3/4 of a wavelength since the green and blue parts are not symmetrical. (Yes, 3/4 wavelength at 160m is no fun :-). My mistake, that should be everything up to 3/8 of a wavelength Sorry -- brain shorted to ground; aftereffects of champagne. 1/2 a wavelength will rotate you completely through 360 degrees. 73 Chen, W7AY __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
On 1/2/2011 2:39 PM, Tony Estep wrote: A short antenna just presents a capacitive reactance (a -j value) to the tuner, which in my experience the KAT3 has always been able to deal with. Well ... I think it sort of depends on the antenna and the length of the feedline if it's surge impedance isn't matched to the antenna feedpoint. Short Marconi-T's and Inv-L's typically will have some inductive reactance when fed at the bottom, hence the usual series cap. And, what Z appears at the TX end of the coax depends both on the mismatch at the feedpoint, and the length of the coax. W3FPR has suggested multiple times that, if all you're looking for is a match by the KAT3 so your K3 will be happy and exude power, try adding 1/8 wave of coax to the line. Of course, just getting a KAT3 match doesn't mean you're getting a lot of power into a short antenna or that it will radiate [or receive] well. I guess there's a reason why those old coastal marine stations had such huge antennas :-) 73, Fred K6DGW - Northern California Contest Club - CU in the 2011 Cal QSO Party 1-2 Oct 2011 - www.cqp.org __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
Chen Thanks for that supporting addition, and for your work on the Smith Chart showing the KAT3 matching range for 160 meters. It is all a matter of the physics of the situation. As you mentioned, the matching range of the KAT3 becomes greater as the frequency is increased. That fact is often overlooked by many hams. It is all about the amount of L and C available in the tuner, but the inductive or capacitive reactance is really what counts in producing the match. If the feedpoint in the shack has 1000 ohms of inductive reactance, and the tuner has only 600 ohms capacitive reactance to attempt to cancel that inductance, then a match will never happen. For a given L, the reactance increases with frequency, and with a given C, the reactance decreases with frequency. That can be easily seen from the formulas for inductive and capacitive reactance - for inductance, the f: term is a multiplier, and for capacitors, it is a divisor. The limiting factor for L-network tuners is usually the largest inductance available. The capacitive component is not normally the limiting factor because that can be made quite small (high reactance). The KAT3 (and KAT100 and KAT2, and KAT1 and KXAT1) uses an L-match tuning section. The required L and C values can easily be computed using the standard formulas for an L-matching section. If the L and C values required are greater than that available in the tuner, you have exceeded the range of the tuner. Instead of adding additional feedline, it is also possible to add parallel or series capacity or inductance at the feedline connection point to bring things into a tunable range. For those who want to pursue the fine points, study a bit about L-networks and conjugate matching. 73, Don W3FPR On 1/2/2011 8:52 PM, Kok Chen wrote: On Jan 2, 2011, at 4:01 PM, Don Wilhelm wrote: Adding or subtracting a 1/8 wavelength of feedline will often bring it into range, and that is normally the easiest solution if the only thing you are considering is the ability of the tuner to produce a match. You can see what Don means by taking a look at this figure (KAT3 at 1.8 MHz, with Smith Chart centered at 50+i0 ohms): http://homepage.mac.com/chen/Technical/Tuner/tuner1.8.png Each point on the Smith Chart is a point that the KAT3 can be brought to an precise SWR of 1.0:1. The blue points are for the KAT3 cap on one side of the inductor and the green points are for the cap switch to the other end of the inductor (the KAT3 is an L tuner, with a relay K17, that switches the caps to one or the other side of the inductor). The center of the Smith Chart circle represents an antenna with an SWR of 1.0:1. As you go out towards the circumference, you have growing circles with the same centers, with ever increasing SWR. Notice (as Don mentioned) that when the SRW is large (towards the circumference of the Smith Chart), there are huge swaths of empty spots in the Smith Chart. These are terminations that the KAT3 can never bring to an SWR of 1.0:1. However (again, as Don mentioned), there are large areas beyond the blue region where you can rotate yourself along on a constant SWR circle and drop yourself right into where the dense green dots are! Voila, ability to tune to an SWR of 1.0:1 while you could not do so without rotating. How do you rotate yourself? A length of transmission line, of course! If you remember your transmission line theory, adding a transmission line will move you along a constant radius circle centered at SWR = 1.0:1. The 1/8 wavelength that Don mentioned will rotate you by 90 degrees. In the case of the K3, you may have to try everything up to about 3/4 of a wavelength since the green and blue parts are not symmetrical. (Yes, 3/4 wavelength at 160m is no fun :-). By the way, if you look carefully, there are SWR values outside of the blue-green Yin-Yang looking region, that are not occupied. I.e., there *will* be antennas that you will never be able to tune even if you try different transmission lines until you are blue in the face. But this plot (again, with reference center at 50 ohms) should quickly tell you which antenna is tunable at 1.8 MHz. If you want to look at the full resolution PDF of the above plot (warning: 9.4 MB), you can use this link: http://homepage.mac.com/chen/Technical/Tuner/tuner1.8.pdf The points are computed by using the capacitor and inductor values of the KAT3. The KAT-100 uses slightly different L and C -- if you are interested in seeing how that tuner works, and can run Xcode on a Mac, I am more than glad to send you the source code that you can modify to produce the PDF chart for a KAT100. The interesting thing about the KAT3 is that as you go up in frequency, the dots become sparser, but do cover the most of the Smith Chart circle out to very high SWR circles. That means that as you go up in frequency, you might not be able
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
Don't you mean to the transmission line? A quarter-wavelength line between the antenna and tuner makes that -j into a +j. Wes N7WS --- On Sun, 1/2/11, Tony Estep estept...@gmail.com wrote: The antenna can be way shorter than 1/2 wave and still tune up fine. No loading scheme is needed. A short antenna just presents a capacitive reactance (a -j value) to the tuner,. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
Sort of sounds logical but it's wrong. Let the load in the shack be 50 +j1000. A low-pass L-net with a shunt Xc = -j501 and series Xl = j1000 will do it. Wes N7WS --- On Sun, 1/2/11, Don Wilhelm w3...@embarqmail.com wrote: As you mentioned, the matching range of the KAT3 becomes greater as the frequency is increased. That fact is often overlooked by many hams. It is all about the amount of L and C available in the tuner, but the inductive or capacitive reactance is really what counts in producing the match. If the feedpoint in the shack has 1000 ohms of inductive reactance, and the tuner has only 600 ohms capacitive reactance to attempt to cancel that inductance, then a match will never happen. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] [K3] KAT3 and 160 with 40m long doublet
Wes, I don't know about the -j501, but Kirchoff tells me that a series Xl = j1000 alone will cancel the +j1000 in the shack feedpoint (your example) leaving a 50 ohms pure resistive load, no need for the shunt element. Since the absolute value of the Low Pass L-net impedance requires that Rl be less than Rs, I do not know how a Low Pass section would provide a match. The matching section must be a High Pass with your values. 73, Don W3FPR On 1/2/2011 10:22 PM, Wes Stewart wrote: Sort of sounds logical but it's wrong. Let the load in the shack be 50 +j1000. A low-pass L-net with a shunt Xc = -j501 and series Xl = j1000 will do it. Wes N7WS --- On Sun, 1/2/11, Don Wilhelmw3...@embarqmail.com wrote: As you mentioned, the matching range of the KAT3 becomes greater as the frequency is increased. That fact is often overlooked by many hams. It is all about the amount of L and C available in the tuner, but the inductive or capacitive reactance is really what counts in producing the match. If the feedpoint in the shack has 1000 ohms of inductive reactance, and the tuner has only 600 ohms capacitive reactance to attempt to cancel that inductance, then a match will never happen. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
