[Elecraft] LDG antenna tuner with 132 foot balanced dipole similar to a G5RV antenna
I recently bought an LDG AT600 Pro Automatic Tuner. I seem to be able to get a low VSWR on 80 40 meters, but on 20, 15, 10 meters the best it will do is ~ 1.8:1. My G5RV (It's really a Van Gordon 80 meter all bander fed with 450 ladder line, 33 feet long, and then transitions to coax thru a 1:1 choke balun; coax is ~ 6 feet long. Has anyone found a configuration that works better on all the bands? Previously I have been using an MFJ 962D manual tuner that is able to tune down below 1.2:1 on all bands. AE6RH K3 S/N 1997 -- Ron Midwin __ 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] LDG antenna tuner with 132 foot balanced dipole similar to a G5RV antenna
Well...maybe the component sizes in the automatic LDG design are coarse enough that your 1:1 values of components is not acheived. Of course a manual tuner has infinite values of continuously variable capacitor and inductor values. Thus it's easier to acheive 1:1. But anyway, why worry about 1.8:1? And how are you measuring SWR? Accurately? So many variables, and 1.8:1 not mattering, I would forget any concern about it. Chuck, KE9UW aka Jack, BMW Motorcycles BMWMOA #224 From: elecraft-boun...@mailman.qth.net [elecraft-boun...@mailman.qth.net] on behalf of Ron Midwin [ronmidwin...@gmail.com] Sent: Friday, October 26, 2012 7:42 AM To: elecraft@mailman.qth.net Subject: [Elecraft] LDG antenna tuner with 132 foot balanced dipole similar to a G5RV antenna I recently bought an LDG AT600 Pro Automatic Tuner. I seem to be able to get a low VSWR on 80 40 meters, but on 20, 15, 10 meters the best it will do is ~ 1.8:1. My G5RV (It's really a Van Gordon 80 meter all bander fed with 450 ladder line, 33 feet long, and then transitions to coax thru a 1:1 choke balun; coax is ~ 6 feet long. Has anyone found a configuration that works better on all the bands? Previously I have been using an MFJ 962D manual tuner that is able to tune down below 1.2:1 on all bands. AE6RH K3 S/N 1997 -- Ron Midwin __ 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] LDG antenna tuner with 132 foot balanced dipole similar to a G5RV antenna
Why not just help the tuner out a little? Put some inductance in series with the center conductor and see if it likes that better. If that doesn't work put some C in series and adjust it. Or some C across the line. Or some L across the line. Or some L in series and C across the line. You get the idea, move the impedance as seen by the tuner to something it can deal with. Rick K2XT __ 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] LDG antenna tuner with 132 foot balanced dipole similar to a G5RV antenna
Ron - This is not an area where I have much experience, but with 450 ohm ladder line I would have thought you would use something other than a 1:1 balun. A few years ago I experimented briefly with an 80 meter dipole, fed with 450 ohm ladder line. I tried it with a 1:1 balun and with a 4:1 balun. An LDG AT-7000 tuned it very easily on 80 through 10 meters while using the 4:1 balun... but had trouble on some bands with the 1:1 balun. Dave - K9FN On Fri, Oct 26, 2012 at 8:42 AM, Ron Midwin ronmidwin...@gmail.com wrote: I recently bought an LDG AT600 Pro Automatic Tuner. I seem to be able to get a low VSWR on 80 40 meters, but on 20, 15, 10 meters the best it will do is ~ 1.8:1. My G5RV (It's really a Van Gordon 80 meter all bander fed with 450 ladder line, 33 feet long, and then transitions to coax thru a 1:1 choke balun; coax is ~ 6 feet long. Has anyone found a configuration that works better on all the bands? Previously I have been using an MFJ 962D manual tuner that is able to tune down below 1.2:1 on all bands. AE6RH K3 S/N 1997 -- Ron Midwin __ 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] LDG antenna tuner with 132 foot balanced dipole similar to a G5RV antenna
Ron, The antenna you have is basically a good one. The problem you get into is that it's really an 80 meter dipole being used on all bands. This has been a popular configuration for many years. The issue is NOT SWR. The issue is transmission line loss in a high SWR situation. To avoid high losses is to use open wire feeds/window line, etc, to the point you get near to your tuner; this is usually at the exterior wall of your house or a window. At that point, you would need to install a 4:1 CURRENT balun. This will do two things. It will keep the feed SWR to a level that should be no problem for your tuner and maintain that there will be no RF current on the exterior of the coax coming into the house; voltage baluns don't always work well if the SWR gets to high. This should work well for you. I use have used this configuration over the years and it has worked for me and other hams that have tried it. Don't get too spun up if the SWR does not get to 1:1. The issue will be is the SWR within the requirements for your transmitter. If the transmitter doesn't care and you do as I suggest, you don't care either. Happy DXing!!! 73, Barry K3NDM On 10/26/2012 8:42 AM, Ron Midwin wrote: I recently bought an LDG AT600 Pro Automatic Tuner. I seem to be able to get a low VSWR on 80 40 meters, but on 20, 15, 10 meters the best it will do is ~ 1.8:1. My G5RV (It's really a Van Gordon 80 meter all bander fed with 450 ladder line, 33 feet long, and then transitions to coax thru a 1:1 choke balun; coax is ~ 6 feet long. Has anyone found a configuration that works better on all the bands? Previously I have been using an MFJ 962D manual tuner that is able to tune down below 1.2:1 on all bands. AE6RH K3 S/N 1997 __ 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] LDG antenna tuner with 132 foot balanced dipole similar to a G5RV antenna
All, There's a trick I learned from an antenna engineer acquaintance recently for tuning 450 ohm feedline's with a 1:1 balun with 50 ohm coax feeding the TX. Here it is: 1. Assemble three RG11 coax lengths. One coax 6 feet 7 inches long, one coax 6 feet long and one coax 9 feet long. From these three coax lengths you can test with four different lengths of 75 ohm coax; 6' 7, 12' 7, 15' 7 and 21' 7. 2. Beginning with the 6' 7 cable and connect the coax between the balun and the 50 ohm feed line, repeat the test below with each of the lengths above. Connect the cables with double female connectors. 3. If you have an analyzer (MFJ analyzers work fine for this) that gives the Rs, Xs and SWR go to step 4; If you don't go to step 6. If you have an AIM 4170 analyzer, you are in luck. The AIM allows you to do single shot analysis of a single frequency, displaying more information than you need for this test. 4. Record the Rs, Xs and SWR of each combination at the frequency you are interested in. A spread sheet makes this a little less tedious. 5. After recording the calculate the SWR the tuner will see with the following rules: Disregard Xs. If the Rs is greater than 50 divide the Rs by 50. if the Rs is less than 50 divide 50 by the Rs. The result will be the SWR the tuner is working against when searching for a match. In my case I am looking for a calculated SWR lower than 10:1 to help my KAT500 tuner find an acceptable match to my KPA500 and NVIS Loop, which works on all amateur bands for close in Non-DX rag chew communications. 6. You can still do the test, but you will need to do it by testing with the tuner for the best combination of matches at each frequency of interest. If you are going to do the tests, remember to use the MINIMUM power your tuner can tune with and allow time for your rig to cool down between tests. 7. When you have completed your tests measure the length of the joined test coaxes, including the double female connectors, and make a piece of RG11 that length. DISCLAMER: I'm not a real technical guy and probably don't know as much antenna theory as many of you, but what I have described worked for me. Your experience may not be the same. Amateur Radio Operator N5GE ARRL Lifetime Member QCWA Lifetime Member On Fri, 26 Oct 2012 05:42:20 -0700, Ron Midwin ronmidwin...@gmail.com wrote: I recently bought an LDG AT600 Pro Automatic Tuner. I seem to be able to get a low VSWR on 80 40 meters, but on 20, 15, 10 meters the best it will do is ~ 1.8:1. My G5RV (It's really a Van Gordon 80 meter all bander fed with 450 ladder line, 33 feet long, and then transitions to coax thru a 1:1 choke balun; coax is ~ 6 feet long. Has anyone found a configuration that works better on all the bands? Previously I have been using an MFJ 962D manual tuner that is able to tune down below 1.2:1 on all bands. AE6RH K3 S/N 1997 __ 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] LDG antenna tuner with 132 foot balanced dipole similar to a G5RV antenna
What is the significance of using RG11 75 ohm coax vs 50 ohm? Sorry if this is a dumb question. Bob AF9W On Oct 26, 2012, at 10:39 AM, N5GE wrote: All, There's a trick I learned from an antenna engineer acquaintance recently for tuning 450 ohm feedline's with a 1:1 balun with 50 ohm coax feeding the TX. Here it is: 1. Assemble three RG11 coax lengths. One coax 6 feet 7 inches long, one coax 6 feet long and one coax 9 feet long. From these three coax lengths you can test with four different lengths of 75 ohm coax; 6' 7, 12' 7, 15' 7 and 21' 7. 2. Beginning with the 6' 7 cable and connect the coax between the balun and the 50 ohm feed line, repeat the test below with each of the lengths above. Connect the cables with double female connectors. 3. If you have an analyzer (MFJ analyzers work fine for this) that gives the Rs, Xs and SWR go to step 4; If you don't go to step 6. If you have an AIM 4170 analyzer, you are in luck. The AIM allows you to do single shot analysis of a single frequency, displaying more information than you need for this test. 4. Record the Rs, Xs and SWR of each combination at the frequency you are interested in. A spread sheet makes this a little less tedious. 5. After recording the calculate the SWR the tuner will see with the following rules: Disregard Xs. If the Rs is greater than 50 divide the Rs by 50. if the Rs is less than 50 divide 50 by the Rs. The result will be the SWR the tuner is working against when searching for a match. In my case I am looking for a calculated SWR lower than 10:1 to help my KAT500 tuner find an acceptable match to my KPA500 and NVIS Loop, which works on all amateur bands for close in Non-DX rag chew communications. 6. You can still do the test, but you will need to do it by testing with the tuner for the best combination of matches at each frequency of interest. If you are going to do the tests, remember to use the MINIMUM power your tuner can tune with and allow time for your rig to cool down between tests. 7. When you have completed your tests measure the length of the joined test coaxes, including the double female connectors, and make a piece of RG11 that length. DISCLAMER: I'm not a real technical guy and probably don't know as much antenna theory as many of you, but what I have described worked for me. Your experience may not be the same. Amateur Radio Operator N5GE ARRL Lifetime Member QCWA Lifetime Member On Fri, 26 Oct 2012 05:42:20 -0700, Ron Midwin ronmidwin...@gmail.com wrote: I recently bought an LDG AT600 Pro Automatic Tuner. I seem to be able to get a low VSWR on 80 40 meters, but on 20, 15, 10 meters the best it will do is ~ 1.8:1. My G5RV (It's really a Van Gordon 80 meter all bander fed with 450 ladder line, 33 feet long, and then transitions to coax thru a 1:1 choke balun; coax is ~ 6 feet long. Has anyone found a configuration that works better on all the bands? Previously I have been using an MFJ 962D manual tuner that is able to tune down below 1.2:1 on all bands. AE6RH K3 S/N 1997 __ 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] LDG antenna tuner with 132 foot balanced dipole similar to a G5RV antenna
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Impedance matching. See http://www.fourier-series.com/rf-concepts/smithchart.html May be more than you wanted to know, but is easy to follow Smith Chart Tutorials. And does explain why you might want to do this. On 10/26/2012 01:23 PM, Bob Stephens wrote: What is the significance of using RG11 75 ohm coax vs 50 ohm? Sorry if this is a dumb question. Bob AF9W - -- /* * Amateur Radio Station AC0HY* * W. Paul Mills SN807* * Assistant EC Alpha-1 ARES Shawnee/Wabunsee, KS * * President Kaw Valley Amateur Radio Club* */ -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://www.enigmail.net/ iEYEARECAAYFAlCK3OMACgkQ5tjVbfWfElwyUQCgg28e0joZ+7FuJgiAad0aTZRD ydMAoInZ9Tki3MgS1NTUW6r9HD8zsi2T =Cil/ -END PGP SIGNATURE- __ 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] LDG antenna tuner with 132 foot balanced dipole similar to a G5RV antenna
All other things being equal, 75-ohm cable has less loss per foot than 50-ohm cable. This assumes that the cables being compared have the same diameter, length, operating frequency, etc. This is the primary reason that cable TV systems, telco inside-plant cabling, and other similar applications use 70-ohm cable. Maximum power handling is obtained by using 30-ohm cable. 50-ohm cable represents the approximate mean between lowest loss and best power handling. - Jim, KL7CC On 10/26/2012 10:23 AM, Bob Stephens wrote: What is the significance of using RG11 75 ohm coax vs 50 ohm? Sorry if this is a dumb question. Bob AF9W On Oct 26, 2012, at 10:39 AM, N5GE wrote: All, There's a trick I learned from an antenna engineer acquaintance recently for tuning 450 ohm feedline's with a 1:1 balun with 50 ohm coax feeding the TX. Here it is: 1. Assemble three RG11 coax lengths. One coax 6 feet 7 inches long, one coax 6 feet long and one coax 9 feet long. From these three coax lengths you can test with four different lengths of 75 ohm coax; 6' 7, 12' 7, 15' 7 and 21' 7. 2. Beginning with the 6' 7 cable and connect the coax between the balun and the 50 ohm feed line, repeat the test below with each of the lengths above. Connect the cables with double female connectors. 3. If you have an analyzer (MFJ analyzers work fine for this) that gives the Rs, Xs and SWR go to step 4; If you don't go to step 6. If you have an AIM 4170 analyzer, you are in luck. The AIM allows you to do single shot analysis of a single frequency, displaying more information than you need for this test. 4. Record the Rs, Xs and SWR of each combination at the frequency you are interested in. A spread sheet makes this a little less tedious. 5. After recording the calculate the SWR the tuner will see with the following rules: Disregard Xs. If the Rs is greater than 50 divide the Rs by 50. if the Rs is less than 50 divide 50 by the Rs. The result will be the SWR the tuner is working against when searching for a match. In my case I am looking for a calculated SWR lower than 10:1 to help my KAT500 tuner find an acceptable match to my KPA500 and NVIS Loop, which works on all amateur bands for close in Non-DX rag chew communications. 6. You can still do the test, but you will need to do it by testing with the tuner for the best combination of matches at each frequency of interest. If you are going to do the tests, remember to use the MINIMUM power your tuner can tune with and allow time for your rig to cool down between tests. 7. When you have completed your tests measure the length of the joined test coaxes, including the double female connectors, and make a piece of RG11 that length. DISCLAMER: I'm not a real technical guy and probably don't know as much antenna theory as many of you, but what I have described worked for me. Your experience may not be the same. Amateur Radio Operator N5GE ARRL Lifetime Member QCWA Lifetime Member On Fri, 26 Oct 2012 05:42:20 -0700, Ron Midwin ronmidwin...@gmail.com wrote: I recently bought an LDG AT600 Pro Automatic Tuner. I seem to be able to get a low VSWR on 80 40 meters, but on 20, 15, 10 meters the best it will do is ~ 1.8:1. My G5RV (It's really a Van Gordon 80 meter all bander fed with 450 ladder line, 33 feet long, and then transitions to coax thru a 1:1 choke balun; coax is ~ 6 feet long. Has anyone found a configuration that works better on all the bands? Previously I have been using an MFJ 962D manual tuner that is able to tune down below 1.2:1 on all bands. AE6RH K3 S/N 1997 __ 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] LDG antenna tuner with 132 foot balanced dipole similar to a G5RV antenna
Sorry, meant to say 75-ohm, not 70-ohm in my previous post. - Jim, KL7CC On 10/26/2012 10:23 AM, Bob Stephens wrote: What is the significance of using RG11 75 ohm coax vs 50 ohm? Sorry if this is a dumb question. Bob AF9W On Oct 26, 2012, at 10:39 AM, N5GE wrote: All, There's a trick I learned from an antenna engineer acquaintance recently for tuning 450 ohm feedline's with a 1:1 balun with 50 ohm coax feeding the TX. Here it is: 1. Assemble three RG11 coax lengths. One coax 6 feet 7 inches long, one coax 6 feet long and one coax 9 feet long. From these three coax lengths you can test with four different lengths of 75 ohm coax; 6' 7, 12' 7, 15' 7 and 21' 7. 2. Beginning with the 6' 7 cable and connect the coax between the balun and the 50 ohm feed line, repeat the test below with each of the lengths above. Connect the cables with double female connectors. 3. If you have an analyzer (MFJ analyzers work fine for this) that gives the Rs, Xs and SWR go to step 4; If you don't go to step 6. If you have an AIM 4170 analyzer, you are in luck. The AIM allows you to do single shot analysis of a single frequency, displaying more information than you need for this test. 4. Record the Rs, Xs and SWR of each combination at the frequency you are interested in. A spread sheet makes this a little less tedious. 5. After recording the calculate the SWR the tuner will see with the following rules: Disregard Xs. If the Rs is greater than 50 divide the Rs by 50. if the Rs is less than 50 divide 50 by the Rs. The result will be the SWR the tuner is working against when searching for a match. In my case I am looking for a calculated SWR lower than 10:1 to help my KAT500 tuner find an acceptable match to my KPA500 and NVIS Loop, which works on all amateur bands for close in Non-DX rag chew communications. 6. You can still do the test, but you will need to do it by testing with the tuner for the best combination of matches at each frequency of interest. If you are going to do the tests, remember to use the MINIMUM power your tuner can tune with and allow time for your rig to cool down between tests. 7. When you have completed your tests measure the length of the joined test coaxes, including the double female connectors, and make a piece of RG11 that length. DISCLAMER: I'm not a real technical guy and probably don't know as much antenna theory as many of you, but what I have described worked for me. Your experience may not be the same. Amateur Radio Operator N5GE ARRL Lifetime Member QCWA Lifetime Member On Fri, 26 Oct 2012 05:42:20 -0700, Ron Midwin ronmidwin...@gmail.com wrote: I recently bought an LDG AT600 Pro Automatic Tuner. I seem to be able to get a low VSWR on 80 40 meters, but on 20, 15, 10 meters the best it will do is ~ 1.8:1. My G5RV (It's really a Van Gordon 80 meter all bander fed with 450 ladder line, 33 feet long, and then transitions to coax thru a 1:1 choke balun; coax is ~ 6 feet long. Has anyone found a configuration that works better on all the bands? Previously I have been using an MFJ 962D manual tuner that is able to tune down below 1.2:1 on all bands. AE6RH K3 S/N 1997 __ 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] LDG antenna tuner with 132 foot balanced dipole similar to a G5RV antenna
The significance of the 75 Ohm line is a matching section that introduces a reciprocal impedance that brings the SWR to 1:1, or nearly so. However, this approach does not address the balanced to unbalanced issue. And, this is generally a one band match. A 1:1 choke type balun will still be needed. The approach may be technically correct, but it is more work than I feel it it is worth. I still suggest the simpler approach I noted earlier as it does work and requires zero engineering knowledge. You just hook up the 450 Ohm ladder line to the antenna on one end and the other goes to the 4:1 current balun. Low loss coax is connected between the tuner and the balun. The operator just tunes the affair until he gets to an acceptable SWR. Nothing else is required, no fiddling around, just operation. 100 feet of 450 line and a few feet of coax will yield losses in the 1-1.5 db range with SWRs up to about around 10:1. This just isn't worth all of the fiddling, IMHO. I try to always adhere to the KISS principle. 73, Barry K3NDM On 10/26/2012 2:23 PM, Bob Stephens wrote: What is the significance of using RG11 75 ohm coax vs 50 ohm? Sorry if this is a dumb question. Bob AF9W On Oct 26, 2012, at 10:39 AM, N5GE wrote: All, There's a trick I learned from an antenna engineer acquaintance recently for tuning 450 ohm feedline's with a 1:1 balun with 50 ohm coax feeding the TX. Here it is: 1. Assemble three RG11 coax lengths. One coax 6 feet 7 inches long, one coax 6 feet long and one coax 9 feet long. From these three coax lengths you can test with four different lengths of 75 ohm coax; 6' 7, 12' 7, 15' 7 and 21' 7. 2. Beginning with the 6' 7 cable and connect the coax between the balun and the 50 ohm feed line, repeat the test below with each of the lengths above. Connect the cables with double female connectors. 3. If you have an analyzer (MFJ analyzers work fine for this) that gives the Rs, Xs and SWR go to step 4; If you don't go to step 6. If you have an AIM 4170 analyzer, you are in luck. The AIM allows you to do single shot analysis of a single frequency, displaying more information than you need for this test. 4. Record the Rs, Xs and SWR of each combination at the frequency you are interested in. A spread sheet makes this a little less tedious. 5. After recording the calculate the SWR the tuner will see with the following rules: Disregard Xs. If the Rs is greater than 50 divide the Rs by 50. if the Rs is less than 50 divide 50 by the Rs. The result will be the SWR the tuner is working against when searching for a match. In my case I am looking for a calculated SWR lower than 10:1 to help my KAT500 tuner find an acceptable match to my KPA500 and NVIS Loop, which works on all amateur bands for close in Non-DX rag chew communications. 6. You can still do the test, but you will need to do it by testing with the tuner for the best combination of matches at each frequency of interest. If you are going to do the tests, remember to use the MINIMUM power your tuner can tune with and allow time for your rig to cool down between tests. 7. When you have completed your tests measure the length of the joined test coaxes, including the double female connectors, and make a piece of RG11 that length. DISCLAMER: I'm not a real technical guy and probably don't know as much antenna theory as many of you, but what I have described worked for me. Your experience may not be the same. Amateur Radio Operator N5GE ARRL Lifetime Member QCWA Lifetime Member On Fri, 26 Oct 2012 05:42:20 -0700, Ron Midwin ronmidwin...@gmail.com wrote: I recently bought an LDG AT600 Pro Automatic Tuner. I seem to be able to get a low VSWR on 80 40 meters, but on 20, 15, 10 meters the best it will do is ~ 1.8:1. My G5RV (It's really a Van Gordon 80 meter all bander fed with 450 ladder line, 33 feet long, and then transitions to coax thru a 1:1 choke balun; coax is ~ 6 feet long. Has anyone found a configuration that works better on all the bands? Previously I have been using an MFJ 962D manual tuner that is able to tune down below 1.2:1 on all bands. AE6RH K3 S/N 1997 __ 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:
Re: [Elecraft] LDG antenna tuner with 132 foot balanced dipole similar to a G5RV antenna
David, I have seen several responses that suggest changes to your antenna setup, but not one that I can warm up to. The choice of a 1:1 balun vs. a 4:1 balun depends on the feedpoint impedance and has nothing to do with the fact that the characteristic impedance of the ladder line is 450 ohms - the impedance at the shack end of that feedline is what is important. If you do not understand what is going on, I direct you to the antenna article on my website www.w3fpr.com, I would strongly suggest that you measure the electrical length of the feedline plus the length of one side of the radiator for all bands of interest. Avoid those sum lengths that are close to a multiple of a half wavelength. Most autotuners do not have the range to work into the high impedance presented by a half wavelength - that goes for 1/2 of a dipole (plus feedline) as well as for an end fed antenna. 73, Don W3FPR On 10/26/2012 10:23 AM, David Bunte wrote: Ron - This is not an area where I have much experience, but with 450 ohm ladder line I would have thought you would use something other than a 1:1 balun. A few years ago I experimented briefly with an 80 meter dipole, fed with 450 ohm ladder line. I tried it with a 1:1 balun and with a 4:1 balun. An LDG AT-7000 tuned it very easily on 80 through 10 meters while using the 4:1 balun... but had trouble on some bands with the 1:1 balun. Dave - K9FN __ 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
