Re: [Elecraft] K3 power reduction due to high SWR
Vic, Before you write off truly balanced tuners in favour of the T-network + balun g, it would be interesting to measure and compare the current in each wire of the feeder (while transmitting a carrier) when using the Matchbox and then the T-network + balun? 73, Geoff LX2AO On April 05, 2012 18:28 +0200, Vic K2VCO wrote: snip But here is the surprising part: I expected that the Matchbox would provide better balance, which would reduce radiation and pickup from the feedline. To test this, I coupled a grid-dip oscillator to the feedline about 20 feet from the tuner. To my great surprise, the signal from the oscillator was much weaker with the T-network + balun than with the Matchbox! Signals the same, 'noise' weaker. So much for the need for 'truly balanced' tuners! __ 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 power reduction due to high SWR
I am not sure I know how to do this. I have a device that I made http://www.qsl.net/k2vco/sniffer/rfsniffer.html to measure current but it gave me anomalous results when I tried it on the matchbox. I found that when I measured the currents about 4 inches from the matchbox they were equal, but when I measured them two feet away they were significantly different. So there is something I don't understand about this process. On 4/6/2012 9:16 AM, Geoffrey Mackenzie-Kennedy wrote: Vic, Before you write off truly balanced tuners in favour of the T-network + balun g, it would be interesting to measure and compare the current in each wire of the feeder (while transmitting a carrier) when using the Matchbox and then the T-network + balun? 73, Geoff LX2AO On April 05, 2012 18:28 +0200, Vic K2VCO wrote: snip But here is the surprising part: I expected that the Matchbox would provide better balance, which would reduce radiation and pickup from the feedline. To test this, I coupled a grid-dip oscillator to the feedline about 20 feet from the tuner. To my great surprise, the signal from the oscillator was much weaker with the T-network + balun than with the Matchbox! Signals the same, 'noise' weaker. So much for the need for 'truly balanced' tuners! -- Vic, K2VCO Fresno CA http://www.qsl.net/k2vco/ __ 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 power reduction due to high SWR
Vic et al, The currents on a particular wire of a two wire feedline, will always be the vector sum of differential current and common mode current. This is not the same thing as forward and reflected, which are both expressed in the differential current. The tuner will be able to control the differential current leaving the tuner. It will NOT be able to control the common mode current. The common mode current can occur because the TERMINATION of the feedline is flawed at the antenna or a balanced to coax junction. Or common mode current can occur simply because it is induced by the antenna, because the feedline is a conductor in the vicinity of the antenna and the relationship of the physical placements of antenna and feedline favor induction. The tuner IMHO is least likely to be the major malefactor in a case of unbalanced currents on a feedline. What occurs out at and toward the feedpoint has been mildly astounding in cases I have helped solve. I have had that problem personally, and had to deal with beating a common mode issue on a balanced line that was putting 900 volts RF across a balun blocking path at QRO and destroying the balun in the process. The common mode path of a balanced feedline is a big antenna, and THE ENTIRE LENGTH of the feedline should be modeled as a single conductor along with the antenna, just to see what is being induced. This includes grounding in the shack if your tuner has a grounded center point which effectively grounds common mode current. Other tuners will present anything from a brute force common mode block to a resistive path to ground. From the tuner's treatment of incoming common mode, its direct grounding, or resistive path to ground, or open circuit to ground, needs to be put in the model. I had to do all of that to dig my way out of my problem. Note, you can't buy broadband RF common mode blocks for balanced line at Radio Shack. Nor anywhere else, for that matter, that I've been able to find. 73, Guy. On Fri, Apr 6, 2012 at 12:24 PM, Vic K2VCO k2vco@gmail.com wrote: I am not sure I know how to do this. I have a device that I made http://www.qsl.net/k2vco/sniffer/rfsniffer.html to measure current but it gave me anomalous results when I tried it on the matchbox. I found that when I measured the currents about 4 inches from the matchbox they were equal, but when I measured them two feet away they were significantly different. So there is something I don't understand about this process. On 4/6/2012 9:16 AM, Geoffrey Mackenzie-Kennedy wrote: Vic, Before you write off truly balanced tuners in favour of the T-network + balun g, it would be interesting to measure and compare the current in each wire of the feeder (while transmitting a carrier) when using the Matchbox and then the T-network + balun? 73, Geoff LX2AO On April 05, 2012 18:28 +0200, Vic K2VCO wrote: snip But here is the surprising part: I expected that the Matchbox would provide better balance, which would reduce radiation and pickup from the feedline. To test this, I coupled a grid-dip oscillator to the feedline about 20 feet from the tuner. To my great surprise, the signal from the oscillator was much weaker with the T-network + balun than with the Matchbox! Signals the same, 'noise' weaker. So much for the need for 'truly balanced' tuners! -- Vic, K2VCO Fresno CA http://www.qsl.net/k2vco/ __ 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 power reduction due to high SWR
Did the Sniffer give you similar anomalous results when you were using the T-network + balun? Also I assume that the indoor run of 450 ohm window line well clear of any object which could affect it. I suggest that we go off List should you like to discuss this further. 73, Geoff LX2AO On April 06, 2012 at 18:24 +0200, Vic K2VCO wrote: I am not sure I know how to do this. I have a device that I made http://www.qsl.net/k2vco/sniffer/rfsniffer.html to measure current but it gave me anomalous results when I tried it on the matchbox. I found that when I measured the currents about 4 inches from the matchbox they were equal, but when I measured them two feet away they were significantly different. So there is something I don't understand about this process. __ 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 power reduction due to high SWR
I use a fan dipole as well (40, 20 and 10), and IIRC from modelling it, putting a 17m wire in the mix really messed up the match. You might want to try removing the 17m dipole and see if there's a better match. Barry W2UP -- View this message in context: http://elecraft.365791.n2.nabble.com/K3-power-reduction-due-to-high-SWR-tp7438699p7439717.html Sent from the Elecraft mailing list archive at Nabble.com. __ 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 power reduction due to high SWR
Dave, Yes well xyl problems can be very tricky to resolve. If money was no barrier a remote K0/K3 setup may have solved the aesthetics issue, and cut the feedline length to small numbers. Not sure how you measured the loss on the 75 ohm coax? A ocf dipole fed with a Balun designs 4115ocf balun will outperform a fan dipole any day, and is less obvious apart from the balun. T Length 41.5m fed 36% point; 27.5m long leg 14m short leg. Worked 4A4A T31A with best VK results using this one antenna for all bands worked. Only you would want to go to low loss 50 ohm coax like lmr etc. Of course balanced line and unbalanced antennas don't mix so coax is necessary with the ocf. The dual core choking - true current 4:1 balun keeps the radiation in the antenna and not the feedline. The antenna develops gain on the long leg lobes on higher bands and for USA a long leg to south and short leg to North would suit your position with some slope to cover nth /sth. Adrian ... vk4tux Adrian, I sent this on the reflector but I thought I would also send it to you directly. The 72 ohm coax I am using is what the cable company used to get from the main line pole to a house. It is about 10 mm or 3/8 in diameter with a carrier wire molded onto it. The coax is not too lossy because I measured the loss when I first installed it several years ago to be sure. I use a choke balun at the feed point made with cores slipped over a 3 ft. piece of RG-213. I must have long runs of transmission line to get my antennas away from my wife's eyes. When I got back into the hobby in 1989 I put up a center fed wire in a field 1,200 feet from my shack near the back of my property and fed it with ladder line and a tuner. Nobody could hear me so I took that down. I still have plenty of ladder line and some great places to put up antennas but they are far away and ladder line cannot lay on the ground in the woods out of sight like coax. Having ladder line in the air hanging off trees or some other supports on the way to an antenna from my house is not acceptable. Maybe I just need to get more creative about placing my dipoles closer to the house and yet out of sight. I am open to any reasonable ideas. Dave - KO4KL -Original Message- From: Adrian [mailto:vk4...@bigpond.com] Sent: Wednesday, April 04, 2012 10:51 PM To: 'David Stratton' Subject: RE: [Elecraft] K3 power reduction due to high SWR You have some serious performance limitations with this setup. If I have to use your antenna, then my move would be to replace the 250' of 75 ohm coax with 250' of 450 ohm ladder line, check the fan dipole legs are exactly the same to provide a balanced load. Get a balun and short 50 ohm coax section to get from the ladder line back into the shack, if you can't get the balanced line in to a balanced line tuner etc. As it is you are losing 57% @ 20m of your power in that feedline. A mfj-986 or similar with balanced line is probably the go on a limited budget. You will reduce loss from 57% to 9%. Adrian ... vk4tux -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of David Stratton Sent: Thursday, 5 April 2012 10:34 AM To: Elecraft Reflector Subject: [Elecraft] K3 power reduction due to high SWR At what point does the SWR have to rise up to before the K3/10 output power begins to decrease? I have been using a TS-830 which is not bothered by SWR up to at least 3:1. I cannot get the tuner now so will I be forced to run very low power if my SWR is 2 or 3 to 1? What about the K3/100? My antennas are resonant fan dipoles (80, 40, 20, 17) fed with 250 feet of 72 ohm cable TV coax. Dave - KO4KL __ 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 power reduction due to high SWR
Adrian, I've been looking at putting up an OCF antenna to replace my 102' doublet fed with ladder line. Can you tell me what frequencies on 80 through 10 meters your OCF antenna is resonant? Also, how much of each band can you cover with less than 2:1 SWR? I'm interested in the CW portions of the bands. Any information would be helpful. By the way, my doublet is currently about 15' off the ground, but I'm considering putting up a 30' center support. 73, Art WB8ENE -- View this message in context: http://elecraft.365791.n2.nabble.com/K3-power-reduction-due-to-high-SWR-tp7438491p7440421.html Sent from the Elecraft mailing list archive at Nabble.com. __ 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 power reduction due to high SWR
Speaking of balanced lines and tuners, I recently did an experiment that surprised me. I have a dipole fed with 600-ohm open-wire line (and some window line indoors). I usually tune it with a Johnson Matchbox, a fully balanced link-coupled tuner. I was lucky enough to get my hands on a massive, high-quality edge-wound rotary inductor in a well-made aluminum enclosure. So I built a high-power T-network tuner with it. I purchased a good (and expensive) 1:1 balun designed for use after a tuner from DX Engineering, and compared the T-net + balun to the Matchbox. I didn't notice any difference in the strength of received signals between the tuners. But here is the surprising part: I expected that the Matchbox would provide better balance, which would reduce radiation and pickup from the feedline. To test this, I coupled a grid-dip oscillator to the feedline about 20 feet from the tuner. To my great surprise, the signal from the oscillator was much weaker with the T-network + balun than with the Matchbox! Signals the same, 'noise' weaker. So much for the need for 'truly balanced' tuners! On 4/5/2012 12:28 AM, Adrian wrote: I disagree, your coax suggestion has 32% loss against a good wl installation which would provide 9% loss. Use of RF ammeter on each leg can be used to balance the loading via antenna leg adjustments if required. A dedicated eg: Johnson matchbox or GQ balanced tuner etc at TX would give good results. The 450 ohm to 72 ohm connection is of no issue centre fed. The ladder line length will have an impedance transformation effect. Trying for common multiple of half wavelengths on FL length -vf at the frequencies used will be a good idea if possible to represent the feedpoint impedance at the TX end if possible. In any case the tuner will take care of the transformation. Any decent low loss coax on this length will cost lots. I assume that the guy can't get the antenna closer, trees in the distance etc probably, but I have seen many good examples from the USA of successful long distance 450 ohm wl runs with wire antenna's. A ladder line setup here will outperform your RG11 etc by 1.2dB. When wet your RG11 setup will have a 1.4dB advantage. I guess it all depends on the weather, and the guys bank balance. 213 is ordinary for coax, I much prefer lmr400, which I use with my BD 4115-ocf. vk4tux -- Vic, K2VCO Fresno CA http://www.qsl.net/k2vco/ __ 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 power reduction due to high SWR
Vic, Where was the frequency of the GDO with respect to the band the tuner was set to? If it was below the band of interest, I would expect something like that - the T-Network is a high pass filter. 73, Don W3FPR On 4/5/2012 12:28 PM, Vic K2VCO wrote: Speaking of balanced lines and tuners, I recently did an experiment that surprised me. I have a dipole fed with 600-ohm open-wire line (and some window line indoors). I usually tune it with a Johnson Matchbox, a fully balanced link-coupled tuner. I was lucky enough to get my hands on a massive, high-quality edge-wound rotary inductor in a well-made aluminum enclosure. So I built a high-power T-network tuner with it. I purchased a good (and expensive) 1:1 balun designed for use after a tuner from DX Engineering, and compared the T-net + balun to the Matchbox. I didn't notice any difference in the strength of received signals between the tuners. But here is the surprising part: I expected that the Matchbox would provide better balance, which would reduce radiation and pickup from the feedline. To test this, I coupled a grid-dip oscillator to the feedline about 20 feet from the tuner. To my great surprise, the signal from the oscillator was much weaker with the T-network + balun than with the Matchbox! Signals the same, 'noise' weaker. So much for the need for 'truly balanced' tuners! __ 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 power reduction due to high SWR
One related question, when speaking of the efficiency of a balanced feedline + balun and tuner, what would be a best/worst case scenario for the loss introduced by the balun+tuner? Would loss vary significantly by frequency for a nonresonant antenna? I'm trying to develop an intuition about the lossiness of the tuner+balun compared to, say, 50' of RG213. I've opted to use a 1:1 balun at the end of 450 ohm ladder line, then a short length of coax into a TenTec 229 tuner. In the informal test that I performed, the homebrew 1:1 balun + coax jumper improved the performance of the antenna compared with connecting it directly to the balanced line connectors on the back of the tuner. 73, Matt NQ6N On Thu, Apr 5, 2012 at 12:23 PM, Don Wilhelm w3...@embarqmail.com wrote: Vic, Where was the frequency of the GDO with respect to the band the tuner was set to? If it was below the band of interest, I would expect something like that - the T-Network is a high pass filter. 73, Don W3FPR On 4/5/2012 12:28 PM, Vic K2VCO wrote: Speaking of balanced lines and tuners, I recently did an experiment that surprised me. I have a dipole fed with 600-ohm open-wire line (and some window line indoors). I usually tune it with a Johnson Matchbox, a fully balanced link-coupled tuner. I was lucky enough to get my hands on a massive, high-quality edge-wound rotary inductor in a well-made aluminum enclosure. So I built a high-power T-network tuner with it. I purchased a good (and expensive) 1:1 balun designed for use after a tuner from DX Engineering, and compared the T-net + balun to the Matchbox. I didn't notice any difference in the strength of received signals between the tuners. But here is the surprising part: I expected that the Matchbox would provide better balance, which would reduce radiation and pickup from the feedline. To test this, I coupled a grid-dip oscillator to the feedline about 20 feet from the tuner. To my great surprise, the signal from the oscillator was much weaker with the T-network + balun than with the Matchbox! Signals the same, 'noise' weaker. So much for the need for 'truly balanced' tuners! __ 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 power reduction due to high SWR
All the tests -- signal comparison and noise tests -- were done on the same band, to which the tuner was tuned (40m). On 4/5/2012 12:23 PM, Don Wilhelm wrote: Vic, Where was the frequency of the GDO with respect to the band the tuner was set to? If it was below the band of interest, I would expect something like that - the T-Network is a high pass filter. 73, Don W3FPR On 4/5/2012 12:28 PM, Vic K2VCO wrote: Speaking of balanced lines and tuners, I recently did an experiment that surprised me. I have a dipole fed with 600-ohm open-wire line (and some window line indoors). I usually tune it with a Johnson Matchbox, a fully balanced link-coupled tuner. I was lucky enough to get my hands on a massive, high-quality edge-wound rotary inductor in a well-made aluminum enclosure. So I built a high-power T-network tuner with it. I purchased a good (and expensive) 1:1 balun designed for use after a tuner from DX Engineering, and compared the T-net + balun to the Matchbox. I didn't notice any difference in the strength of received signals between the tuners. But here is the surprising part: I expected that the Matchbox would provide better balance, which would reduce radiation and pickup from the feedline. To test this, I coupled a grid-dip oscillator to the feedline about 20 feet from the tuner. To my great surprise, the signal from the oscillator was much weaker with the T-network + balun than with the Matchbox! Signals the same, 'noise' weaker. So much for the need for 'truly balanced' tuners! -- Vic, K2VCO Fresno CA http://www.qsl.net/k2vco/ __ 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 power reduction due to high SWR
Most tuner losses occur in the same way as feed line losses - resistive losses in the conductors. In a tuner, that is usually in the inductance. The higher the current, the greater the resistive losses. That's why high impedance feed lines such as open wire line have typically much less loss than 50 ohm coaxial line. Higher impedance means higher voltages and less current for a given power. (Excepting the use of some ladder line that has very small gauge conductors which offset at least some of its advantage). Tuners that must feed very low impedance loads often suffer losses in the inductors due to the high currents required. Some tuners such as the popular T-network type may have more than one combination of settings that will provide a match. One setting can produce much more current and so greater loss than the other. W9CF wrote a Java simulator that lets you see the predicted losses for various conditions. Just twirl the knobs and watch the SWR or let it auto-tune for a given load and frequency: http://fermi.la.asu.edu/w9cf/tuner/tuner.html 73, Ron AC7AC -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Matt Murphy Sent: Thursday, April 05, 2012 12:53 PM To: d...@w3fpr.com Cc: Vic K2VCO; elecraft@mailman.qth.net Subject: Re: [Elecraft] K3 power reduction due to high SWR One related question, when speaking of the efficiency of a balanced feedline + balun and tuner, what would be a best/worst case scenario for the loss introduced by the balun+tuner? Would loss vary significantly by frequency for a nonresonant antenna? I'm trying to develop an intuition about the lossiness of the tuner+balun compared to, say, 50' of RG213. I've opted to use a 1:1 balun at the end of 450 ohm ladder line, then a short length of coax into a TenTec 229 tuner. In the informal test that I performed, the homebrew 1:1 balun + coax jumper improved the performance of the antenna compared with connecting it directly to the balanced line connectors on the back of the tuner. 73, Matt NQ6N On Thu, Apr 5, 2012 at 12:23 PM, Don Wilhelm w3...@embarqmail.com wrote: Vic, Where was the frequency of the GDO with respect to the band the tuner was set to? If it was below the band of interest, I would expect something like that - the T-Network is a high pass filter. 73, Don W3FPR On 4/5/2012 12:28 PM, Vic K2VCO wrote: Speaking of balanced lines and tuners, I recently did an experiment that surprised me. I have a dipole fed with 600-ohm open-wire line (and some window line indoors). I usually tune it with a Johnson Matchbox, a fully balanced link-coupled tuner. I was lucky enough to get my hands on a massive, high-quality edge-wound rotary inductor in a well-made aluminum enclosure. So I built a high-power T-network tuner with it. I purchased a good (and expensive) 1:1 balun designed for use after a tuner from DX Engineering, and compared the T-net + balun to the Matchbox. I didn't notice any difference in the strength of received signals between the tuners. But here is the surprising part: I expected that the Matchbox would provide better balance, which would reduce radiation and pickup from the feedline. To test this, I coupled a grid-dip oscillator to the feedline about 20 feet from the tuner. To my great surprise, the signal from the oscillator was much weaker with the T-network + balun than with the Matchbox! Signals the same, 'noise' weaker. So much for the need for 'truly balanced' tuners! __ 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 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 power reduction due to high SWR
Thanks Ron for the great explanation. 73 On Thu, Apr 5, 2012 at 1:41 PM, Ron D'Eau Claire r...@cobi.biz wrote: Most tuner losses occur in the same way as feed line losses - resistive losses in the conductors. In a tuner, that is usually in the inductance. The higher the current, the greater the resistive losses. That's why high impedance feed lines such as open wire line have typically much less loss than 50 ohm coaxial line. Higher impedance means higher voltages and less current for a given power. (Excepting the use of some ladder line that has very small gauge conductors which offset at least some of its advantage). Tuners that must feed very low impedance loads often suffer losses in the inductors due to the high currents required. Some tuners such as the popular T-network type may have more than one combination of settings that will provide a match. One setting can produce much more current and so greater loss than the other. W9CF wrote a Java simulator that lets you see the predicted losses for various conditions. Just twirl the knobs and watch the SWR or let it auto-tune for a given load and frequency: http://fermi.la.asu.edu/w9cf/tuner/tuner.html 73, Ron AC7AC -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Matt Murphy Sent: Thursday, April 05, 2012 12:53 PM To: d...@w3fpr.com Cc: Vic K2VCO; elecraft@mailman.qth.net Subject: Re: [Elecraft] K3 power reduction due to high SWR One related question, when speaking of the efficiency of a balanced feedline + balun and tuner, what would be a best/worst case scenario for the loss introduced by the balun+tuner? Would loss vary significantly by frequency for a nonresonant antenna? I'm trying to develop an intuition about the lossiness of the tuner+balun compared to, say, 50' of RG213. I've opted to use a 1:1 balun at the end of 450 ohm ladder line, then a short length of coax into a TenTec 229 tuner. In the informal test that I performed, the homebrew 1:1 balun + coax jumper improved the performance of the antenna compared with connecting it directly to the balanced line connectors on the back of the tuner. 73, Matt NQ6N On Thu, Apr 5, 2012 at 12:23 PM, Don Wilhelm w3...@embarqmail.com wrote: Vic, Where was the frequency of the GDO with respect to the band the tuner was set to? If it was below the band of interest, I would expect something like that - the T-Network is a high pass filter. 73, Don W3FPR On 4/5/2012 12:28 PM, Vic K2VCO wrote: Speaking of balanced lines and tuners, I recently did an experiment that surprised me. I have a dipole fed with 600-ohm open-wire line (and some window line indoors). I usually tune it with a Johnson Matchbox, a fully balanced link-coupled tuner. I was lucky enough to get my hands on a massive, high-quality edge-wound rotary inductor in a well-made aluminum enclosure. So I built a high-power T-network tuner with it. I purchased a good (and expensive) 1:1 balun designed for use after a tuner from DX Engineering, and compared the T-net + balun to the Matchbox. I didn't notice any difference in the strength of received signals between the tuners. But here is the surprising part: I expected that the Matchbox would provide better balance, which would reduce radiation and pickup from the feedline. To test this, I coupled a grid-dip oscillator to the feedline about 20 feet from the tuner. To my great surprise, the signal from the oscillator was much weaker with the T-network + balun than with the Matchbox! Signals the same, 'noise' weaker. So much for the need for 'truly balanced' tuners! __ 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 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 power reduction due to high SWR
Interesting! The balun I made is just a basic core type current balun modeled after the one listed here (but made with high temp wire inside teflon tubing): http://vk5ajl.com/projects/baluns.php#current On Thu, Apr 5, 2012 at 2:15 PM, Adrian vk4...@bigpond.com wrote: The external balun you are using is probably better than the one built into the tuner. An English ham did research some time back and found using a 1:1 current balun less lossy that a 4:1 or others, despite the line mismatch the tuner made up for it with tested less total loss. With a well designed tuner/balun combo the circulating current is much less, and it is only the resistance component that provides loss, not inductive nor capacitive. vk4tux -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Matt Murphy Sent: Friday, 6 April 2012 5:53 AM To: d...@w3fpr.com Cc: Vic K2VCO; elecraft@mailman.qth.net Subject: Re: [Elecraft] K3 power reduction due to high SWR One related question, when speaking of the efficiency of a balanced feedline + balun and tuner, what would be a best/worst case scenario for the loss introduced by the balun+tuner? Would loss vary significantly by frequency for a nonresonant antenna? I'm trying to develop an intuition about the lossiness of the tuner+balun compared to, say, 50' of RG213. I've opted to use a 1:1 balun at the end of 450 ohm ladder line, then a short length of coax into a TenTec 229 tuner. In the informal test that I performed, the homebrew 1:1 balun + coax jumper improved the performance of the antenna compared with connecting it directly to the balanced line connectors on the back of the tuner. 73, Matt NQ6N On Thu, Apr 5, 2012 at 12:23 PM, Don Wilhelm w3...@embarqmail.com wrote: Vic, Where was the frequency of the GDO with respect to the band the tuner was set to? If it was below the band of interest, I would expect something like that - the T-Network is a high pass filter. 73, Don W3FPR On 4/5/2012 12:28 PM, Vic K2VCO wrote: Speaking of balanced lines and tuners, I recently did an experiment that surprised me. I have a dipole fed with 600-ohm open-wire line (and some window line indoors). I usually tune it with a Johnson Matchbox, a fully balanced link-coupled tuner. I was lucky enough to get my hands on a massive, high-quality edge-wound rotary inductor in a well-made aluminum enclosure. So I built a high-power T-network tuner with it. I purchased a good (and expensive) 1:1 balun designed for use after a tuner from DX Engineering, and compared the T-net + balun to the Matchbox. I didn't notice any difference in the strength of received signals between the tuners. But here is the surprising part: I expected that the Matchbox would provide better balance, which would reduce radiation and pickup from the feedline. To test this, I coupled a grid-dip oscillator to the feedline about 20 feet from the tuner. To my great surprise, the signal from the oscillator was much weaker with the T-network + balun than with the Matchbox! Signals the same, 'noise' weaker. So much for the need for 'truly balanced' tuners! __ 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 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 power reduction due to high SWR
Dave, The KPA3 will throttle back power at or above the SWR = 2.0 point. Actually, I am not certain about the K3/10 - it may or may not reduce power above SWR = 2.0,. but I would suggest that your goal for antenna tuning be less than SWR = 2.0. I you have resonant antennas, then it should be a good thing to tune them for less than a 2-1 SWR, but if you are using a properly tuned multiband antenna, you should already have an SWR less than 2-1. If you are using a non-resonant antenna, you already have a tuner installed - just set the tuner for the lowest reflected power possible. 73, Don W3FPR On 4/4/2012 8:33 PM, David Stratton wrote: At what point does the SWR have to rise up to before the K3/10 output power begins to decrease? I have been using a TS-830 which is not bothered by SWR up to at least 3:1. I cannot get the tuner now so will I be forced to run very low power if my SWR is 2 or 3 to 1? What about the K3/100? My antennas are resonant fan dipoles (80, 40, 20, 17) fed with 250 feet of 72 ohm cable TV coax. Dave - KO4KL __ 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 power reduction due to high SWR
It all depends on just what he means by 72 ohm cable TV coax. If it's the low quality coax used around your TV's, you might be right. But if it's the 1/2 CATV hardline or the smaller drop cable, the loss will be much less. These last two are quite good and have very low loss. I have used just under 300' and did quite well with both QRP and QRPp. It used to be that you could go to your local cable TV company and get lots of left over pieces of that good coax. No idea how that works now but sure worth a try. So Dave, I'd say to use whatever you have and get on the air. Then spend the rest of your life making your antennas bigger, higher and better! OK, back in my hole, Ron, KU7Y SOWP 5545M Arizona Outlaws Contest Club Brenda, AZ (Winter) Caldwell, ID (Summer) k...@qsl.net http://www.hatpinsandmore.com - Original Message - From: Adrian vk4...@bigpond.com To: elecraft@mailman.qth.net Sent: 04 April, 2012 8:00 PM Subject: [Elecraft] K3 power reduction due to high SWR You have some serious performance limitations with this setup. If I have to use your antenna, then my move would be to replace the 250' of 75 ohm coax with 250' of 450 ohm ladder line, check the fan dipole legs are exactly the same to provide a balanced load. Get a balun and short 50 ohm coax section to get from the ladder line back into the shack, if you can't get the balanced line in to a balanced line tuner etc. As it is you are losing 57% @ 20m of your power in that feedline. A mfj-986 or similar with balanced line is probably the go on a limited budget. You will reduce loss from 57% to 9%. Adrian ... vk4tux -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of David Stratton Sent: Thursday, 5 April 2012 10:34 AM To: Elecraft Reflector Subject: [Elecraft] K3 power reduction due to high SWR At what point does the SWR have to rise up to before the K3/10 output power begins to decrease? I have been using a TS-830 which is not bothered by SWR up to at least 3:1. I cannot get the tuner now so will I be forced to run very low power if my SWR is 2 or 3 to 1? What about the K3/100? My antennas are resonant fan dipoles (80, 40, 20, 17) fed with 250 feet of 72 ohm cable TV coax. Dave - KO4KL __ 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 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 power reduction due to high SWR
If I have to use your antenna, then my move would be to replace the 250' of75 ohm coax with 250' of 450 ohm ladder line, check the fan dipole legs are exactly the same to provide a balanced load. You're on target about loss in the feedline, but ladder line is not a good move here.David has resonant dipoles, so they are a pretty good match to 50 or 75 ohm cable. Folks think QRP, so they think small coax, But when the line is as long as these are, the loss certainly gets out of hand unless it's bigger coax. If I were to make ANY change in the feedline, it would be to a decent RG8 or RG11. I would also look at ways to reduce the length of the line by finding a shorter route to the shack. You don't need expensive coax -- Davis 213 is about as good as it gets for the HF bands, and it's fairly inexpensive. Window line is NOT the cure for all ills -- it is as lossy as small coax when it gets wet, and there's some loss (and cost) in any impedance transforming balun. Further, most real antennas are unbalanced by their surroundings, so they need a good ferrite common mode choke at the feedpoint whether they're fed by coax or parallel wire line. 73, Jim Brown 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
