Balanced solution for KAT500 tuner?
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Balanced solution for KAT500 tuner?
 
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Does Elecraft have a balun solution for balanced feeders for the KAT500 at 500 watts?
Steve Barry University at Buffalo Police Bissell Hall, Amherst Campus Tel: 716,645-2228 or 645-8910 Cell: 716,207-9494 FAX: 716,645-3758 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Balanced solution for KAT500 tuner?
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On 9/29/2012 5:40 AM, Barry, Stephen wrote:
> Does Elecraft have a balun solution for balanced feeders for the KAT500 at 500 watts? See the Choke Cookbook that is Chapter 8 in my RFI Tutorial, and the discussion in the preceding pages, for an excellent common mode choke that will satisfy this need. Use one of the chokes that is bifilar wound with #12 THHN, connected as a parallel wire transmission line between your parallel wire line and the tuner. http://audiosystemsgroup.com/RFI-Ham.pdf BTW -- the words "balanced feeders" and "balanced feedline" are pure fiction. You will note that I used the words "parallel wire" to describe the feedline. The balance of any system, including an antenna system, is defined equal impedances to the reference plane. For antenna systems not on aircraft, that reference plane is the earth, and the transmission line is only part of that system. Most wire antennas that hams are able to erect are unbalanced by their surroundings, which in turn causes the feedline to be unbalanced. Imbalance in an antenna is caused by off-center feed, ground slope, sloping wires, trees, buildings, even the varying ground conductivity around the antenna. This imbalance will cause current on the feedline to become unbalanced, which makes it part of the antenna. The feedline picks up noise and couples it to the antenna (because it's part of the antenna). For this reason alone, smart hams have learned to use a common mode choke at the feedpoint of an antenna This decouples the feedline from the antenna, preventing noise pickup (and keeping RF out of the shack). 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Hi,
So are you suggesting using a choke balun on both ends of the parallel wire feedline? AB2TC - Knut
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I have the same question. The parallel wire feeder can pick up noise also by itself.
Bob K6UJ On Sep 29, 2012, at 11:10 AM, ab2tc wrote: > Hi, > > So are you suggesting using a choke balun on both ends of the parallel wire > feedline? > > AB2TC - Knut > > > Jim Brown-10 wrote >> On 9/29/2012 5:40 AM, Barry, Stephen wrote: >>> Does Elecraft have a balun solution for balanced feeders for the KAT500 >>> at 500 watts? >> >> See the Choke Cookbook that is Chapter 8 in my RFI Tutorial, and the >> discussion in the preceding pages, for an excellent common mode choke >> that will satisfy this need. Use one of the chokes that is bifilar >> wound with #12 THHN, connected as a parallel wire transmission line >> between your parallel wire line and the tuner. >> >> http://audiosystemsgroup.com/RFI-Ham.pdf >> >> BTW -- the words "balanced feeders" and "balanced feedline" are pure >> fiction. You will note that I used the words "parallel wire" to describe >> the feedline. >> >> The balance of any system, including an antenna system, is defined equal >> impedances to the reference plane. For antenna systems not on aircraft, >> that reference plane is the earth, and the transmission line is only >> part of that system. Most wire antennas that hams are able to erect are >> unbalanced by their surroundings, which in turn causes the feedline to >> be unbalanced. Imbalance in an antenna is caused by off-center feed, >> ground slope, sloping wires, trees, buildings, even the varying ground >> conductivity around the antenna. >> >> This imbalance will cause current on the feedline to become unbalanced, >> which makes it part of the antenna. The feedline picks up noise and >> couples it to the antenna (because it's part of the antenna). >> >> For this reason alone, smart hams have learned to use a common mode >> choke at the feedpoint of an antenna This decouples the feedline from >> the antenna, preventing noise pickup (and keeping RF out of the shack). >> >> 73, Jim K9YC >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto: > >> Elecraft@.qth > >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html > > > > > > -- > View this message in context: http://elecraft.365791.n2.nabble.com/Balanced-solution-for-KAT500-tuner-tp7563429p7563442.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:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by ab2tc
I have the same question. The parallel wire feeder can pick up noise also by itself.
Bob K6UJ On Sep 29, 2012, at 11:10 AM, ab2tc wrote: > Hi, > > So are you suggesting using a choke balun on both ends of the parallel wire > feedline? > > AB2TC - Knut > > > Jim Brown-10 wrote >> On 9/29/2012 5:40 AM, Barry, Stephen wrote: >>> Does Elecraft have a balun solution for balanced feeders for the KAT500 >>> at 500 watts? >> >> See the Choke Cookbook that is Chapter 8 in my RFI Tutorial, and the >> discussion in the preceding pages, for an excellent common mode choke >> that will satisfy this need. Use one of the chokes that is bifilar >> wound with #12 THHN, connected as a parallel wire transmission line >> between your parallel wire line and the tuner. >> >> http://audiosystemsgroup.com/RFI-Ham.pdf >> >> BTW -- the words "balanced feeders" and "balanced feedline" are pure >> fiction. You will note that I used the words "parallel wire" to describe >> the feedline. >> >> The balance of any system, including an antenna system, is defined equal >> impedances to the reference plane. For antenna systems not on aircraft, >> that reference plane is the earth, and the transmission line is only >> part of that system. Most wire antennas that hams are able to erect are >> unbalanced by their surroundings, which in turn causes the feedline to >> be unbalanced. Imbalance in an antenna is caused by off-center feed, >> ground slope, sloping wires, trees, buildings, even the varying ground >> conductivity around the antenna. >> >> This imbalance will cause current on the feedline to become unbalanced, >> which makes it part of the antenna. The feedline picks up noise and >> couples it to the antenna (because it's part of the antenna). >> >> For this reason alone, smart hams have learned to use a common mode >> choke at the feedpoint of an antenna This decouples the feedline from >> the antenna, preventing noise pickup (and keeping RF out of the shack). >> >> 73, Jim K9YC >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto: > >> Elecraft@.qth > >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html > > > > > > -- > View this message in context: http://elecraft.365791.n2.nabble.com/Balanced-solution-for-KAT500-tuner-tp7563429p7563442.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:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Jim Brown-10
Jim...
Is there anything to be gained in putting a 1:1 "balanced isolator" at the feed point of an antenna that is fed by a "parallel wire" feed line? Does such an arrangement achieve feed line isolation while preserving the ability of such an antenna to be driven on various bands other than its resonant frequency? Thanks for your input. ...robert > > For this reason alone, smart hams have learned to use a common mode > choke at the feedpoint of an antenna This decouples the feedline from > the antenna, preventing noise pickup (and keeping RF out of the shack). > > 73, Jim K9YC > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > -- Robert G. Strickland, PhD, ABPH - KE2WY [hidden email] Syracuse, New York, USA ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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1:1 current balun has proven more efficient in conjunction with the
appropriate balanced (matchbox style)tuner. -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Robert G. Strickland Sent: Sunday, 30 September 2012 4:26 AM To: [hidden email] Subject: Re: [Elecraft] Balanced solution for KAT500 tuner? Jim... Is there anything to be gained in putting a 1:1 "balanced isolator" at the feed point of an antenna that is fed by a "parallel wire" feed line? Does such an arrangement achieve feed line isolation while preserving the ability of such an antenna to be driven on various bands other than its resonant frequency? Thanks for your input. ...robert > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Balanced solution for KAT500 tuner?
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In reply to this post by ab2tc
On 9/29/2012 11:10 AM, ab2tc wrote:
> So are you suggesting using a choke balun on both ends of the parallel wire > feedline? Not just a suggestion, but a STRONG recommendation. But leave the word "balun" out of this sentence. It is a COMMON MODE CHOKE -- a section of parallel wire line wound around a lossy ferrite core that forms a very low Q resonant circuit. The parallel resistance at resonance is what chokes off common mode current. The word "balun" is highly confusing, because it is used to describe at least a half dozen very different circuit elements -- everything from tuned lengths of transmission line to actual transformers, to arrays of common mode chokes, to electronic circuitry to modulate baseband video onto CAT5 cable. . 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Balanced solution for KAT500 tuner?
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In reply to this post by RobertG
On 9/29/2012 11:26 AM, Robert G. Strickland wrote:
> Is there anything to be gained in putting a 1:1 "balanced isolator" at the feed point > of an antenna that is fed by a "parallel wire" feed line? Does such an arrangement > achieve feed line isolation while preserving the ability of such an antenna to be > driven on various bands other than its resonant frequency? Thanks for your input. Phrases and words like "balanced isolator" and "balun" are not only confusing, they are used to separate people from their money. The chokes described in my RFI tutorial can be built for the price of a single #31 core, a few yards of THHN wire, and a couple of connectors. You can put it in a box if you like, but it's only cosmetic. These chokes will handle legal power IF the antennas are not badly unbalanced. Off-center feed creates massive imbalance, and will fry even the best of chokes. The relatively small imbalances created by surrounding objects will not -- they simply couple noise. #31 cores cost about $4.50 in 1,000 lots, about $7 if you buy 100, and $15 from the rip-off vendors who advertise in QST. It's become fairly common for ham clubs to get together and make a group purchase. Over a period of about 8 years, I've been part of several at the 1,000-piece level. There are guidelines in Appendix One of the tutorial about how and where to buy. It's worth buying in quantity, because these 2.4-in diameter cores are almost universally useful for RFI suppression. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Balanced solution for KAT500 tuner?
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In reply to this post by vk4tux
On 9/29/2012 2:13 PM, Adrian wrote:
> 1:1 current balun has proven more efficient in conjunction with the > appropriate balanced (matchbox style)tuner. With good choke at the feedpoint and at the input to an unbalanced tuner, there should be NO advantage to using the balanced tuner. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Jim Brown-10
Can someone point me to where the cables are sold and information to connect the K3 to the VL-1000 for band data input? Fred/N0AZZ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: K3/Yaesu VL-1000 amp Cable
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I don't know of anyone who sells such cables. Information on building them is still available on N0SS's (sk) web site: http://www.n0ss.net/k3-to-quadra_08jan2010.pdf 73, ... Joe, W4TV On 9/29/2012 5:53 PM, Fred Smith wrote: > > Can someone point me to where the cables are sold and information to connect > the K3 to the VL-1000 for band data input? > > Fred/N0AZZ > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Balanced solution for KAT500 tuner?
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In reply to this post by vk4tux
I don't believe that is necessarily true. Can you cite a reference to back up that statement? Or at least describe in physical terms (Q, currents, voltages, component loss, etc) why that would be so? I'm honestly curious what the difference would be. 73, Dave AB7E On 9/29/2012 2:13 PM, Adrian wrote: > 1:1 current balun has proven more efficient in conjunction with the > appropriate balanced (matchbox style)tuner. > > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Robert G. Strickland > Sent: Sunday, 30 September 2012 4:26 AM > To: [hidden email] > Subject: Re: [Elecraft] Balanced solution for KAT500 tuner? > > Jim... > > Is there anything to be gained in putting a 1:1 "balanced isolator" at the > feed point of an antenna that is fed by a "parallel wire" feed line? Does > such an arrangement achieve feed line isolation while preserving the ability > of such an antenna to be driven on various bands other than its resonant > frequency? Thanks for your input. > > ...robert > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Joe Subich, W4TV-4
Thanks Joe for the link.
Fred/N0AZZ Sent from my iPhone On Sep 29, 2012, at 5:12 PM, "Joe Subich, W4TV" <[hidden email]> wrote: > > I don't know of anyone who sells such cables. Information on building > them is still available on N0SS's (sk) web site: > http://www.n0ss.net/k3-to-quadra_08jan2010.pdf > > > 73, > > ... Joe, W4TV > > > On 9/29/2012 5:53 PM, Fred Smith wrote: >> >> Can someone point me to where the cables are sold and information to connect >> the K3 to the VL-1000 for band data input? >> >> Fred/N0AZZ >> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[hidden email] >> >> 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:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by David Gilbert
A UK G call did a graphed efficiency comparison test with the 1:1 coming out
on top. I will post it when re-found. Also from http://www.theladderline.com/doublets-ladder-line-and-automatic-remote-tuner s ; (spell-checked) "There is also some debate about whether the balun should be a 1:1 or 4:1. I think 4:1 has been quite popular in the past. This perhaps comes from the thought that the ladder line is higher impedance than coax so we need to step down to get it closer to the coax impedance. On the forums, people who have modelled the antenna with software like EZNEC seem to make a fairly compelling argument that a 1:1 balun is more likely to present an impedance within the range of the tuner over a wide range of frequencies. The impedance will depend on the length of the ladder line so it's a bit of a gamble but I'm getting good results from a 1:1 current balun. After doing some reading and playing with a home brew balun, I finally took the lazy way out and splashed out on a serious balun. It's a DX Engineering BAL050-H10-AT. It's not cheap but I think it was a good investment. I don't have any hard evidence to show how good it is compared to a cheaper balun but I have a feeling that it contributes to the good performance I get with this antenna. I've had absolutely no "RF in the shack" or similar problems even at the old QTH when I had the ladder line coming into the shack. An interesting fact that I learned from the forums is the reason ladder line works more successfully than coax in a multiband situation like this. The common belief is that ladder line "doesn't care" about high SWR. It's true that ladder line usually has lower loss than coax at a given SWR but that's not the whole story. Another rather simple factor is that the characteristic impedance of ladder line is higher than coax so therefore, for a typical wire antenna over a wide range of frequency, the average SWR on ladder line tends to be lower than it would be with coax and that helps keep the loss low." -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of David Gilbert Sent: Sunday, 30 September 2012 8:37 AM To: [hidden email] Subject: Re: [Elecraft] Balanced solution for KAT500 tuner? I don't believe that is necessarily true. Can you cite a reference to back up that statement? Or at least describe in physical terms (Q, currents, voltages, component loss, etc) why that would be so? I'm honestly curious what the difference would be. 73, Dave AB7E On 9/29/2012 2:13 PM, Adrian wrote: > 1:1 current balun has proven more efficient in conjunction with the > appropriate balanced (matchbox style)tuner. > > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Robert G. > Strickland > Sent: Sunday, 30 September 2012 4:26 AM > To: [hidden email] > Subject: Re: [Elecraft] Balanced solution for KAT500 tuner? > > Jim... > > Is there anything to be gained in putting a 1:1 "balanced isolator" at > the feed point of an antenna that is fed by a "parallel wire" feed > line? Does such an arrangement achieve feed line isolation while > preserving the ability of such an antenna to be driven on various > bands other than its resonant frequency? Thanks for your input. > > ...robert > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by David Gilbert
Another supportive example;
"One is not always better than the other, but my choice for general purpose use would be a 1:1 current balun for better ATU loss near current maximum." http://vk1od.net/balun/concept/4to1.htm -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of David Gilbert Sent: Sunday, 30 September 2012 8:37 AM To: [hidden email] Subject: Re: [Elecraft] Balanced solution for KAT500 tuner? I don't believe that is necessarily true. Can you cite a reference to back up that statement? Or at least describe in physical terms (Q, currents, voltages, component loss, etc) why that would be so? I'm honestly curious what the difference would be. 73, Dave AB7E On 9/29/2012 2:13 PM, Adrian wrote: > 1:1 current balun has proven more efficient in conjunction with the > appropriate balanced (matchbox style)tuner. > > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Robert G. > Strickland > Sent: Sunday, 30 September 2012 4:26 AM > To: [hidden email] > Subject: Re: [Elecraft] Balanced solution for KAT500 tuner? > > Jim... > > Is there anything to be gained in putting a 1:1 "balanced isolator" at > the feed point of an antenna that is fed by a "parallel wire" feed > line? Does such an arrangement achieve feed line isolation while > preserving the ability of such an antenna to be driven on various > bands other than its resonant frequency? Thanks for your input. > > ...robert > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by David Gilbert
Here:
http://www.karinya.net/g3txq/tuner_balun/ "Amateur Radio (G3TXQ) - Tuner Balun: 4:1 or 1:1 ? Follow the discussions on any Internet Ham Radio forum and it wont be long before someone recommends the use of a 4:1 balun at the output of a tuner feeding a multiband doublet through ladderline. Often the recommendation is accompanied by an explanation such as: "It helps the tuner to tune" or: "It reduces the impedance of the 450 ohm ladderline towards 50Ω". This article examines whether the ubiquitous advice to use a 4:1 balun in this scenario is valid. The arguments put forward for a 4:1 impedance transformation often assume that the tuner works best when operating with a load impedance close to 50Ω. That simply isn't true! The chart on the right shows the losses vs load resistance of a typical T-network tuner on 80m for several values of load reactance; 80m was chosen because losses tend to be more evident on the lower-frequency bands. As we can see the lowest tuner losses occur when the load resistance is in the medium/high range 250Ω-2500Ω; the highest losses occur at low load resistances, particularly where they are accompanied by a large capacitive reactance. Let's now take the example of a commonly proposed multiband doublet - a half-wave 80m dipole fed with 450Ω ladderline. At modest heights above average ground the dipole has a feedpoint impedance close to 50Ω. That means that the impedance seen at the tuner end of the ladderline could have a resistive component anywhere from 50Ω to 4050Ω depending on ladderline length; that range of impedances is indicated by the lower shaded bar in the chart, labelled 1:1. If we now introduce a 4:1 impedance transformation, the range of impedances will be lower by a factor of 4 as indicated by the upper shaded bar labelled 4:1. It's clear that the 1:1 range of impedances will result in the lower overall losses. In fact, no matter what the antenna impedance, the range of impedances seen at the tuner end of the ladderline would have a "geometric mean" of 450Ω - that is they would swing equally below and above 450Ω, but once we introduce a 4:1 balun the geometric mean will reduce to 112.5Ω. One look at the loss chart tells you that centering the impedances at the higher value is the preferable option. Let's now take a look at the specific losses that would occur with our example 132 doublet fed with 450Ω ladderline. The chart on the right was produced by varying the feedline length from 0° to 180° in 10° steps. At each step the impedance seen by the tuner was calculated both with a 1:1 balun and then with a 4:1 balun, and the tuner losses determined using W9CF's T-network tuner simulator. Of course, beyond 180° the chart simply repeats itself. Ladderline losses were ignored. Apart from a small range of line lengths between 80° and 115°, where the line has transformed the 50Ω feedpoint impedance to a very high value around 4000Ω, the 1:1 balun is the better option; not only that, the worst case loss never exceeds 14% with the 1:1 balun whereas it reaches 21% with the 4:1 balun. But what about other bands - the doublet wont be used on just 80m! This chart shows the tuner loss plotted against line length for our example doublet on 40m. Here the doublet feedpoint impedance is around 4000Ω, so for short ladderline lengths the 4:1 balun shows an advantage. However, as the ladderline length increases and the impedance is transformed to lower values, the 1:1 balun soon shows the lower losses again. Across the whole range of ladderline lengths the 1:1 balun is twice as likely as the 4:1 to produce lower losses. The conclusion seems clear: if you have to choose just one balun, unless you know that your combination of doublet/ladderline length falls into the minority of cases where a 4:1 balun has the advantage, a 1:1 balun is the preferred choice. Add into the mix the fact that most 4:1 baluns are Voltage Baluns, whereas to prevent feedline radiation we want balanced currents; then consider that all baluns other than a 1:1 Current Balun have the full transmit voltage applied common-mode across one or more windings, and the case is compelling for a 1:1 Current Balun in this situation. In this application any small impedance transformation caused by the Current Balun is immaterial because the tuner will compensate, so the windings do not need to be of any specific characteristic impedance. Typically, bifilar windings using Thermaleze wire inserted in Teflon tubes are employed to cope with the high differential-mode voltages present at current minima. Balun specialists "Balun Designs" offer a nice example in their Model 1171. " -----Original Message----- From: Adrian [mailto:[hidden email]] Sent: Sunday, 30 September 2012 9:34 AM To: [hidden email] Subject: RE: [Elecraft] Balanced solution for KAT500 tuner? A UK G call did a graphed efficiency comparison test with the 1:1 coming out on top. I will post it when re-found. Also from http://www.theladderline.com/doublets-ladder-line-and-automatic-remote-tuner s ; (spell-checked) "There is also some debate about whether the balun should be a 1:1 or 4:1. I think 4:1 has been quite popular in the past. This perhaps comes from the thought that the ladder line is higher impedance than coax so we need to step down to get it closer to the coax impedance. On the forums, people who have modelled the antenna with software like EZNEC seem to make a fairly compelling argument that a 1:1 balun is more likely to present an impedance within the range of the tuner over a wide range of frequencies. The impedance will depend on the length of the ladder line so it's a bit of a gamble but I'm getting good results from a 1:1 current balun. After doing some reading and playing with a home brew balun, I finally took the lazy way out and splashed out on a serious balun. It's a DX Engineering BAL050-H10-AT. It's not cheap but I think it was a good investment. I don't have any hard evidence to show how good it is compared to a cheaper balun but I have a feeling that it contributes to the good performance I get with this antenna. I've had absolutely no "RF in the shack" or similar problems even at the old QTH when I had the ladder line coming into the shack. An interesting fact that I learned from the forums is the reason ladder line works more successfully than coax in a multiband situation like this. The common belief is that ladder line "doesn't care" about high SWR. It's true that ladder line usually has lower loss than coax at a given SWR but that's not the whole story. Another rather simple factor is that the characteristic impedance of ladder line is higher than coax so therefore, for a typical wire antenna over a wide range of frequency, the average SWR on ladder line tends to be lower than it would be with coax and that helps keep the loss low." -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of David Gilbert Sent: Sunday, 30 September 2012 8:37 AM To: [hidden email] Subject: Re: [Elecraft] Balanced solution for KAT500 tuner? I don't believe that is necessarily true. Can you cite a reference to back up that statement? Or at least describe in physical terms (Q, currents, voltages, component loss, etc) why that would be so? I'm honestly curious what the difference would be. 73, Dave AB7E On 9/29/2012 2:13 PM, Adrian wrote: > 1:1 current balun has proven more efficient in conjunction with the > appropriate balanced (matchbox style)tuner. > > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Robert G. > Strickland > Sent: Sunday, 30 September 2012 4:26 AM > To: [hidden email] > Subject: Re: [Elecraft] Balanced solution for KAT500 tuner? > > Jim... > > Is there anything to be gained in putting a 1:1 "balanced isolator" at > the feed point of an antenna that is fed by a "parallel wire" feed > line? Does such an arrangement achieve feed line isolation while > preserving the ability of such an antenna to be driven on various > bands other than its resonant frequency? Thanks for your input. > > ...robert > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Balanced solution for KAT500 tuner?
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In reply to this post by David Gilbert
Sorry for any confusion. I thought you were trying to say that a balanced antenna tuner with a balanced current choke was generally more efficient than an unbalanced tuner with a balanced current choke. Was that your intent? If so, why? 73, Dave AB7E On 9/29/2012 3:37 PM, David Gilbert wrote: > I don't believe that is necessarily true. Can you cite a reference to > back up that statement? Or at least describe in physical terms (Q, > currents, voltages, component loss, etc) why that would be so? I'm > honestly curious what the difference would be. > > 73, > Dave AB7E > > > > On 9/29/2012 2:13 PM, Adrian wrote: >> 1:1 current balun has proven more efficient in conjunction with the >> appropriate balanced (matchbox style)tuner. >> >> -----Original Message----- >> From: [hidden email] >> [mailto:[hidden email]] On Behalf Of Robert G. Strickland >> Sent: Sunday, 30 September 2012 4:26 AM >> To: [hidden email] >> Subject: Re: [Elecraft] Balanced solution for KAT500 tuner? >> >> Jim... >> >> Is there anything to be gained in putting a 1:1 "balanced isolator" at the >> feed point of an antenna that is fed by a "parallel wire" feed line? Does >> such an arrangement achieve feed line isolation while preserving the ability >> of such an antenna to be driven on various bands other than its resonant >> frequency? Thanks for your input. >> >> ...robert >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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It comprises as per conjunction; the input;
http://www.palstar.com/manual_bt1500a.pdf "Input balun 1:1 current type balun Impedance Range 2500 +/- j2500 160 m to 20 m (assuming Resistive load) 1000 +/- j1000 17m to 10m A single-ended L-network - the most common variety - uses a certain value of inductance (L) and a certain value of capacitance (C) to effect a match at a particular frequency for a particular antenna feedline impedance and length. For coaxial cable systems, the single-ended L-network provides the lowest loss of any network matching system. However, one limitation is that with the capacitor on the antenna side of the coil, the system is limited to antenna terminal impedances greater than about 50 Ohms. If we wish to use the single-ended network with a balanced feedline, we have to add a balun on the output side of the network. Baluns work best with very low values of reactance on their output terminals, a condition that is difficult to obtain with most antennas that use parallel feedlines. The balanced version of the L-network overcomes this limitation by providing a true balanced output directly from the network. For a particular antenna, operating frequency, and transmission line impedance and length, the matching circuit requires the same total circuit inductance and the same output capacitance as the single-ended network. However, the balanced circuit divides the inductance into two equal series portions, one in each leg of the network. The shunt capacitor has the same value in both versions of the L-network. Unlike the single-ended L-network, the legs of the balanced L-network are both above ground potential. Hence, both the input and antenna sides of the network are balanced. In order to accommodate the single-ended transmission line from the transmitter, the tuner places a 1:1 choke (current) balun between the input side of the network and the transmitter coax connector. The balun converts the unbalanced input from the transmitter to a balanced condition for the network. As well, it suppresses currents that might otherwise appear on the braid of the transmitter cable." -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of David Gilbert Sent: Sunday, 30 September 2012 10:57 AM To: [hidden email] Subject: Re: [Elecraft] Balanced solution for KAT500 tuner? Sorry for any confusion. I thought you were trying to say that a balanced antenna tuner with a balanced current choke was generally more efficient than an unbalanced tuner with a balanced current choke. Was that your intent? If so, why? 73, Dave AB7E On 9/29/2012 3:37 PM, David Gilbert wrote: > I don't believe that is necessarily true. Can you cite a reference to > back up that statement? Or at least describe in physical terms (Q, > currents, voltages, component loss, etc) why that would be so? I'm > honestly curious what the difference would be. > > 73, > Dave AB7E > > > > On 9/29/2012 2:13 PM, Adrian wrote: >> 1:1 current balun has proven more efficient in conjunction with the >> appropriate balanced (matchbox style)tuner. >> >> -----Original Message----- >> From: [hidden email] >> [mailto:[hidden email]] On Behalf Of Robert G. >> Strickland >> Sent: Sunday, 30 September 2012 4:26 AM >> To: [hidden email] >> Subject: Re: [Elecraft] Balanced solution for KAT500 tuner? >> >> Jim... >> >> Is there anything to be gained in putting a 1:1 "balanced isolator" >> at the feed point of an antenna that is fed by a "parallel wire" feed >> line? Does such an arrangement achieve feed line isolation while >> preserving the ability of such an antenna to be driven on various >> bands other than its resonant frequency? Thanks for your input. >> >> ...robert >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: Balanced solution for KAT500 tuner?
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In reply to this post by vk4tux
Many hams *asssume* that because the feedline character8istic impedance
is 450 ohms, that it will work better with a 4:1 balun. Nothing could be further from the truth, the impedance seen at the shack end of the feedline can vary from quite high to quite low - the feedline works as a transmission line tuner (and the ATU does too). For powers up to 100 watts, I suggest the Elecraft BL2 which provides a switch to change from 1:1 to 4:1. Use the setting that provides the best results. 73, Don W3FPR On 9/29/2012 7:41 PM, Adrian wrote: > Here: > > http://www.karinya.net/g3txq/tuner_balun/ > > "Amateur Radio (G3TXQ) - Tuner Balun: 4:1 or 1:1 ? > > Follow the discussions on any Internet Ham Radio forum and it wont be long > before someone recommends the use of a 4:1 balun at the output of a tuner > feeding a multiband doublet through ladderline. Often the recommendation is > accompanied by an explanation such as: "It helps the tuner to tune" or: "It > reduces the impedance of the 450 ohm ladderline towards 50Ω". This article > examines whether the ubiquitous advice to use a 4:1 balun in this scenario > is valid. > > The arguments put forward for a 4:1 impedance transformation often assume > that the tuner works best when operating with a load impedance close to 50Ω. > That simply isn't true! The chart on the right shows the losses vs load > resistance of a typical T-network tuner on 80m for several values of load > reactance; 80m was chosen because losses tend to be more evident on the > lower-frequency bands. As we can see the lowest tuner losses occur when the > load resistance is in the medium/high range 250Ω-2500Ω; the highest losses > occur at low load resistances, particularly where they are accompanied by a > large capacitive reactance. > > Let's now take the example of a commonly proposed multiband doublet - a > half-wave 80m dipole fed with 450Ω ladderline. At modest heights above > average ground the dipole has a feedpoint impedance close to 50Ω. That means > that the impedance seen at the tuner end of the ladderline could have a > resistive component anywhere from 50Ω to 4050Ω depending on ladderline > length; that range of impedances is indicated by the lower shaded bar in the > chart, labelled 1:1. If we now introduce a 4:1 impedance transformation, the > range of impedances will be lower by a factor of 4 as indicated by the upper > shaded bar labelled 4:1. It's clear that the 1:1 range of impedances will > result in the lower overall losses. > > In fact, no matter what the antenna impedance, the range of impedances seen > at the tuner end of the ladderline would have a "geometric mean" of 450Ω - > that is they would swing equally below and above 450Ω, but once we introduce > a 4:1 balun the geometric mean will reduce to 112.5Ω. One look at the loss > chart tells you that centering the impedances at the higher value is the > preferable option. > > > Let's now take a look at the specific losses that would occur with our > example 132 doublet fed with 450Ω ladderline. > > The chart on the right was produced by varying the feedline length from 0° > to 180° in 10° steps. At each step the impedance seen by the tuner was > calculated both with a 1:1 balun and then with a 4:1 balun, and the tuner > losses determined using W9CF's T-network tuner simulator. Of course, beyond > 180° the chart simply repeats itself. Ladderline losses were ignored. > > Apart from a small range of line lengths between 80° and 115°, where the > line has transformed the 50Ω feedpoint impedance to a very high value around > 4000Ω, the 1:1 balun is the better option; not only that, the worst case > loss never exceeds 14% with the 1:1 balun whereas it reaches 21% with the > 4:1 balun. > > But what about other bands - the doublet wont be used on just 80m! > > > This chart shows the tuner loss plotted against line length for our example > doublet on 40m. Here the doublet feedpoint impedance is around 4000Ω, so for > short ladderline lengths the 4:1 balun shows an advantage. However, as the > ladderline length increases and the impedance is transformed to lower > values, the 1:1 balun soon shows the lower losses again. Across the whole > range of ladderline lengths the 1:1 balun is twice as likely as the 4:1 to > produce lower losses. > > The conclusion seems clear: if you have to choose just one balun, unless you > know that your combination of doublet/ladderline length falls into the > minority of cases where a 4:1 balun has the advantage, a 1:1 balun is the > preferred choice. Add into the mix the fact that most 4:1 baluns are Voltage > Baluns, whereas to prevent feedline radiation we want balanced currents; > then consider that all baluns other than a 1:1 Current Balun have the full > transmit voltage applied common-mode across one or more windings, and the > case is compelling for a 1:1 Current Balun in this situation. > > In this application any small impedance transformation caused by the Current > Balun is immaterial because the tuner will compensate, so the windings do > not need to be of any specific characteristic impedance. Typically, bifilar > windings using Thermaleze wire inserted in Teflon tubes are employed to cope > with the high differential-mode voltages present at current minima. Balun > specialists "Balun Designs" offer a nice example in their Model 1171. > " > > -----Original Message----- > From: Adrian [mailto:[hidden email]] > Sent: Sunday, 30 September 2012 9:34 AM > To: [hidden email] > Subject: RE: [Elecraft] Balanced solution for KAT500 tuner? > > A UK G call did a graphed efficiency comparison test with the 1:1 coming out > on top. I will post it when re-found. > > Also from > http://www.theladderline.com/doublets-ladder-line-and-automatic-remote-tuner > s ; (spell-checked) > > "There is also some debate about whether the balun should be a 1:1 or 4:1. I > think 4:1 has been quite popular in the past. This perhaps comes from the > thought that the ladder line is higher impedance than coax so we need to > step down to get it closer to the coax impedance. On the forums, people who > have modelled the antenna with software like EZNEC seem to make a fairly > compelling argument that a 1:1 balun is more likely to present an impedance > within the range of the tuner over a wide range of frequencies. The > impedance will depend on the length of the ladder line so it's a bit of a > gamble but I'm getting good results from a 1:1 current balun. > > After doing some reading and playing with a home brew balun, I finally took > the lazy way out and splashed out on a serious balun. It's a DX Engineering > BAL050-H10-AT. It's not cheap but I think it was a good investment. I don't > have any hard evidence to show how good it is compared to a cheaper balun > but I have a feeling that it contributes to the good performance I get with > this antenna. I've had absolutely no "RF in the shack" or similar problems > even at the old QTH when I had the ladder line coming into the shack. > > An interesting fact that I learned from the forums is the reason ladder line > works more successfully than coax in a multiband situation like this. The > common belief is that ladder line "doesn't care" about high SWR. It's true > that ladder line usually has lower loss than coax at a given SWR but that's > not the whole story. Another rather simple factor is that the characteristic > impedance of ladder line is higher than coax so therefore, for a typical > wire antenna over a wide range of frequency, the average SWR on ladder line > tends to be lower than it would be with coax and that helps keep the loss > low." > > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of David Gilbert > Sent: Sunday, 30 September 2012 8:37 AM > To: [hidden email] > Subject: Re: [Elecraft] Balanced solution for KAT500 tuner? > > > I don't believe that is necessarily true. Can you cite a reference to back > up that statement? Or at least describe in physical terms (Q, currents, > voltages, component loss, etc) why that would be so? I'm honestly curious > what the difference would be. > > 73, > Dave AB7E > > > > On 9/29/2012 2:13 PM, Adrian wrote: >> 1:1 current balun has proven more efficient in conjunction with the >> appropriate balanced (matchbox style)tuner. >> >> -----Original Message----- >> From: [hidden email] >> [mailto:[hidden email]] On Behalf Of Robert G. >> Strickland >> Sent: Sunday, 30 September 2012 4:26 AM >> To: [hidden email] >> Subject: Re: [Elecraft] Balanced solution for KAT500 tuner? >> >> Jim... >> >> Is there anything to be gained in putting a 1:1 "balanced isolator" at >> the feed point of an antenna that is fed by a "parallel wire" feed >> line? Does such an arrangement achieve feed line isolation while >> preserving the ability of such an antenna to be driven on various >> bands other than its resonant frequency? Thanks for your input. >> >> ...robert >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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