K3 ATU Tune
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I am trying to learn the behavior of the K3 ATU Tune. I am switching between two loads. One is dummy load with SWR of about 1.1. The other is a mismatch on an antenna with a measured SWR of about 4.9 (as read off of the LP-100A meter). I am attempting to use the ATU Tune button to bring this unmatched SWR load into a match of 1.5 or under.
So, I am getting strange results. I can use my external AT1KM tuner to bring this into a flat 1:1 SWR. If I press the K3 ATU Tune button I also get the 1:1 SWR reading (or close to it, one bar on the K3 SWR display plut the LP-100A reads 1:1). If I switch the tuner out of service (into a bypass mode where the K3 is looking at a 4.9:1 SWR), I use the K3 to hit XMIT briefly and read out the 4.9 SWR. At this point, it looks like I get a fold back on power of about 50 percent (operating at 10 watts so fold back to 5 watts I guess). The next thing I do is switch the AT1KM tuner back into service without changing anything. When I key down I am getting SWR of 1:1 on the LP-100A and the K3 but the power is still folded back. If I hit the K3 Tune button, it quickly tunes and the power is back to full power (or, 10 watts). So, my question --- If the K3 folds back power due to high SWR then is it required to hit the tune button to reset power when you now have a matched load, 1:1 in this case? I hope I have explained the situation, it is a little involved in set up but I ran across this accidentally while measuring some different antenna loads. Also, I am not sure I am reading the SWR on the K3 correctly. If I hit the tune button for one of my antennas (in this case different from above scenario) and NO EXTERNAL TUNER, The K3 tunes and a single bar shows up on the SWR display which I figure is either 1:1 or close to it. But, I have an LP-100A sitting on the output of my K-line (I have a KPA500 in there but it is not on during these tests) and the LP-100A gives an SWR reading of 1.73:1. Who do I believe? The LP-100A was calibrated at the factory (not a kit). Thanks, 73, phil, K7PEH ______________________________________________________________ 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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Phil, The LP-100A (or any external SWR/power measurement device) is not accurate when you are using the KAT3 (K3 internal ATU) since it is on the *output* of the tuner and not the *input*. A tuner *DOES NOT CHANGE THE SWR BETWEEN THE TUNER AND ANTENNA* it only changes the SWR seen by any device looking at the *input* of the tuner. With the KAT3 the *input* to the tuner is "inside* the K3. 73, ... Joe, W4TV On 4/23/2012 3:17 PM, Phil Hystad wrote: > I am trying to learn the behavior of the K3 ATU Tune. I am switching between two loads. One is dummy load with SWR of about 1.1. The other is a mismatch on an antenna with a measured SWR of about 4.9 (as read off of the LP-100A meter). I am attempting to use the ATU Tune button to bring this unmatched SWR load into a match of 1.5 or under. > > So, I am getting strange results. I can use my external AT1KM tuner to bring this into a flat 1:1 SWR. If I press the K3 ATU Tune button I also get the 1:1 SWR reading (or close to it, one bar on the K3 SWR display plut the LP-100A reads 1:1). If I switch the tuner out of service (into a bypass mode where the K3 is looking at a 4.9:1 SWR), I use the K3 to hit XMIT briefly and read out the 4.9 SWR. At this point, it looks like I get a fold back on power of about 50 percent (operating at 10 watts so fold back to 5 watts I guess). The next thing I do is switch the AT1KM tuner back into service without changing anything. When I key down I am getting SWR of 1:1 on the LP-100A and the K3 but the power is still folded back. If I hit the K3 Tune button, it quickly tunes and the power is back to full power (or, 10 watts). > > So, my question --- If the K3 folds back power due to high SWR then is it required to hit the tune button to reset power when you now have a matched load, 1:1 in this case? > > I hope I have explained the situation, it is a little involved in set up but I ran across this accidentally while measuring some different antenna loads. > > Also, I am not sure I am reading the SWR on the K3 correctly. If I hit the tune button for one of my antennas (in this case different from above scenario) and NO EXTERNAL TUNER, The K3 tunes and a single bar shows up on the SWR display which I figure is either 1:1 or close to it. But, I have an LP-100A sitting on the output of my K-line (I have a KPA500 in there but it is not on during these tests) and the LP-100A gives an SWR reading of 1.73:1. Who do I believe? The LP-100A was calibrated at the factory (not a kit). > > Thanks, > > 73, phil, K7PEH > > ______________________________________________________________ > 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 Phil Hystad-3
Phil,
Actually you can believe both the K3 and the LP-100A. The KAT3 is inside the K3, and the SWR it reads is that at the INPUT to the tuner. Tuning the internal K3 tuner will *not* change the SWR on the outside of the K3, it will still be whatever you read on the LP-100A - that is the impedance of your antenna or whatever is connected to the LP-100 output. 73, Don W3FPR On 4/23/2012 3:17 PM, Phil Hystad wrote: > I am trying to learn the behavior of the K3 ATU Tune. I am switching between two loads. One is dummy load with SWR of about 1.1. The other is a mismatch on an antenna with a measured SWR of about 4.9 (as read off of the LP-100A meter). I am attempting to use the ATU Tune button to bring this unmatched SWR load into a match of 1.5 or under. > > So, I am getting strange results. I can use my external AT1KM tuner to bring this into a flat 1:1 SWR. If I press the K3 ATU Tune button I also get the 1:1 SWR reading (or close to it, one bar on the K3 SWR display plut the LP-100A reads 1:1). If I switch the tuner out of service (into a bypass mode where the K3 is looking at a 4.9:1 SWR), I use the K3 to hit XMIT briefly and read out the 4.9 SWR. At this point, it looks like I get a fold back on power of about 50 percent (operating at 10 watts so fold back to 5 watts I guess). The next thing I do is switch the AT1KM tuner back into service without changing anything. When I key down I am getting SWR of 1:1 on the LP-100A and the K3 but the power is still folded back. If I hit the K3 Tune button, it quickly tunes and the power is back to full power (or, 10 watts). > > So, my question --- If the K3 folds back power due to high SWR then is it required to hit the tune button to reset power when you now have a matched load, 1:1 in this case? > > I hope I have explained the situation, it is a little involved in set up but I ran across this accidentally while measuring some different antenna loads. > > Also, I am not sure I am reading the SWR on the K3 correctly. If I hit the tune button for one of my antennas (in this case different from above scenario) and NO EXTERNAL TUNER, The K3 tunes and a single bar shows up on the SWR display which I figure is either 1:1 or close to it. But, I have an LP-100A sitting on the output of my K-line (I have a KPA500 in there but it is not on during these tests) and the LP-100A gives an SWR reading of 1.73:1. Who do I believe? The LP-100A was calibrated at the factory (not a kit). > 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
About my second question on the different readings of the K3 ATU and the LP-100A. Gosh Darn It -- I knew that. I was not thinking. I had been doing so many different measurements this morning that when that came about (the different readings), I was surprised but it was obviously not a problem. I just repeated the measurement and yes, the raw SWR is 1.73:1 and the K3 Tuned to a flat 1:1 yet the LP-100A is reading the raw SWR.
But, actually that was not my main question. The thing that prompted me to ask send the message was the first question about the fold back on power and if it needs the K3 ATU Tune button to be pressed to reset even though the load is well matched and should not fold back at all. 73, phil, K7PEH On Apr 23, 2012, at 12:24 PM, Joe Subich, W4TV wrote: > > Phil, > > The LP-100A (or any external SWR/power measurement device) is not > accurate when you are using the KAT3 (K3 internal ATU) since it is > on the *output* of the tuner and not the *input*. > > A tuner *DOES NOT CHANGE THE SWR BETWEEN THE TUNER AND ANTENNA* it > only changes the SWR seen by any device looking at the *input* of > the tuner. With the KAT3 the *input* to the tuner is "inside* the > K3. > > 73, > > ... Joe, W4TV > > > On 4/23/2012 3:17 PM, Phil Hystad wrote: >> I am trying to learn the behavior of the K3 ATU Tune. I am switching between two loads. One is dummy load with SWR of about 1.1. The other is a mismatch on an antenna with a measured SWR of about 4.9 (as read off of the LP-100A meter). I am attempting to use the ATU Tune button to bring this unmatched SWR load into a match of 1.5 or under. >> >> So, I am getting strange results. I can use my external AT1KM tuner to bring this into a flat 1:1 SWR. If I press the K3 ATU Tune button I also get the 1:1 SWR reading (or close to it, one bar on the K3 SWR display plut the LP-100A reads 1:1). If I switch the tuner out of service (into a bypass mode where the K3 is looking at a 4.9:1 SWR), I use the K3 to hit XMIT briefly and read out the 4.9 SWR. At this point, it looks like I get a fold back on power of about 50 percent (operating at 10 watts so fold back to 5 watts I guess). The next thing I do is switch the AT1KM tuner back into service without changing anything. When I key down I am getting SWR of 1:1 on the LP-100A and the K3 but the power is still folded back. If I hit the K3 Tune button, it quickly tunes and the power is back to full power (or, 10 watts). >> >> So, my question --- If the K3 folds back power due to high SWR then is it required to hit the tune button to reset power when you now have a matched load, 1:1 in this case? >> >> I hope I have explained the situation, it is a little involved in set up but I ran across this accidentally while measuring some different antenna loads. >> >> Also, I am not sure I am reading the SWR on the K3 correctly. If I hit the tune button for one of my antennas (in this case different from above scenario) and NO EXTERNAL TUNER, The K3 tunes and a single bar shows up on the SWR display which I figure is either 1:1 or close to it. But, I have an LP-100A sitting on the output of my K-line (I have a KPA500 in there but it is not on during these tests) and the LP-100A gives an SWR reading of 1.73:1. Who do I believe? The LP-100A was calibrated at the factory (not a kit). >> >> Thanks, >> >> 73, phil, K7PEH >> >> ______________________________________________________________ >> 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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> The thing that prompted me to ask send the message was the first > question about the fold back on power and if it needs the K3 ATU > Tune button to be pressed to reset even though the load is well > matched and should not fold back at all. I don't understand this question. If you have engaged the KAT3 and it has been unable to tune the load satisfactorily and the K3 goes into foldback, the load will remain improperly tuned until the KAT3 is tuned again to find a satisfactory set of matching conditions (if such a set exists). If one tunes a mismatched load then substitutes a properly matched load for the mismatched one without readjusting the tuner, the K3 may fold back because the "good" load is being transformed to a bad one just the way the "bad" one had been transformed to a "good" load. I *think* the answer to your question is that the tuner must be bypassed (or adjusted for a 50 Ohm to 50 Ohm transformation) any time you connect a "well matched" load. If you fail to bypass the tuner, the "well matched load" is no longer matched to the output condition of the KAT3. 73, ... Joe, W4TV On 4/23/2012 4:08 PM, Phil Hystad wrote: > About my second question on the different readings of the K3 ATU and the LP-100A. Gosh Darn It -- I knew that. I was not thinking. I had been doing so many different measurements this morning that when that came about (the different readings), I was surprised but it was obviously not a problem. I just repeated the measurement and yes, the raw SWR is 1.73:1 and the K3 Tuned to a flat 1:1 yet the LP-100A is reading the raw SWR. > > But, actually that was not my main question. The thing that prompted me to ask send the message was the first question about the fold back on power and if it needs the K3 ATU Tune button to be pressed to reset even though the load is well matched and should not fold back at all. > > 73, phil, K7PEH > > > On Apr 23, 2012, at 12:24 PM, Joe Subich, W4TV wrote: > >> >> Phil, >> >> The LP-100A (or any external SWR/power measurement device) is not >> accurate when you are using the KAT3 (K3 internal ATU) since it is >> on the *output* of the tuner and not the *input*. >> >> A tuner *DOES NOT CHANGE THE SWR BETWEEN THE TUNER AND ANTENNA* it >> only changes the SWR seen by any device looking at the *input* of >> the tuner. With the KAT3 the *input* to the tuner is "inside* the >> K3. >> >> 73, >> >> ... Joe, W4TV >> >> >> On 4/23/2012 3:17 PM, Phil Hystad wrote: >>> I am trying to learn the behavior of the K3 ATU Tune. I am switching between two loads. One is dummy load with SWR of about 1.1. The other is a mismatch on an antenna with a measured SWR of about 4.9 (as read off of the LP-100A meter). I am attempting to use the ATU Tune button to bring this unmatched SWR load into a match of 1.5 or under. >>> >>> So, I am getting strange results. I can use my external AT1KM tuner to bring this into a flat 1:1 SWR. If I press the K3 ATU Tune button I also get the 1:1 SWR reading (or close to it, one bar on the K3 SWR display plut the LP-100A reads 1:1). If I switch the tuner out of service (into a bypass mode where the K3 is looking at a 4.9:1 SWR), I use the K3 to hit XMIT briefly and read out the 4.9 SWR. At this point, it looks like I get a fold back on power of about 50 percent (operating at 10 watts so fold back to 5 watts I guess). The next thing I do is switch the AT1KM tuner back into service without changing anything. When I key down I am getting SWR of 1:1 on the LP-100A and the K3 but the power is still folded back. If I hit the K3 Tune button, it quickly tunes and the power is back to full power (or, 10 watts). >>> >>> So, my question --- If the K3 folds back power due to high SWR then is it required to hit the tune button to reset power when you now have a matched load, 1:1 in this case? >>> >>> I hope I have explained the situation, it is a little involved in set up but I ran across this accidentally while measuring some different antenna loads. >>> >>> Also, I am not sure I am reading the SWR on the K3 correctly. If I hit the tune button for one of my antennas (in this case different from above scenario) and NO EXTERNAL TUNER, The K3 tunes and a single bar shows up on the SWR display which I figure is either 1:1 or close to it. But, I have an LP-100A sitting on the output of my K-line (I have a KPA500 in there but it is not on during these tests) and the LP-100A gives an SWR reading of 1.73:1. Who do I believe? The LP-100A was calibrated at the factory (not a kit). >>> >>> Thanks, >>> >>> 73, phil, K7PEH >>> >>> ______________________________________________________________ >>> 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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