k3 SWR readings seem generous
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I have been working on antennas today and have a puzzle. I am finding that
the K3 SWR indications are unbelievable generous. With my 40M inverted V fed with RG8X (50 ohm) coax I see that the K3 seems generous in the SWR indication on tune with ATU bypassed. I have noticed a slight change in SWR with K3 power setting so the following was taken with K3 tune power set to 100 watts. If I set it to 10 watts the discrepancy is greater... SWR SWR SWR Freq. K3 VA1 Daiwa 7.00 MHz 1.3 1.92 2.0 7.05 MHz 1.2 1.92 1.9 7.1 MHz 1.2 1.98 1.95 7.15 MHz 1.3 2.26 2.1 7.2 MHz 1.9 2.60 2.3 7.25 MHz 1.5 2.88 2.6 7.3 MHz 1.6 3.32 2.7 The Daiwa is the CN-101L cross needle meter. The VA1 is the Autek Rx Vector antenna analyzer. The VA1 does not have a tuned input so it is possible that it can be fooled by local broadcast stations. I don't suspect this issue here as there aren't any close by broadcast stations that I am aware of. The Daiwa and the VA1 tend to agree pretty well anyway. The K3 measurements are the outliers. This antenna on a "Tenna Dipper" shows minimal SWR at 7.040 MHz, just where I tuned it a few years ago. The LED does not extinguish indicating higher than 1:1 SWR at the minimum. If you look at the numbers, I guess I don't believe the K3, Do you think my antenna is below 1.6 to 1 across the entire 40M band? So now on to 20M dipole fed with RG58 (50 Ohm Coax)... The Tenna Dipper fully extinguishes at 13.805 MHz indicating that my antenna is bit too long but is close to 1:1 at that frequency. Freq K3 VA1 Daiwa 13.81 -- 1.12 -- 14.0 MHz 1.1 1.24 1.31 14.1 MHz 1.1 1.30 1.70 14.2 MHz 1.1 1.55 1.85 14.3 MHz 1.2 1.69 1.85 RG58 may have some losses on this band so perhaps all of the SWR indications are generous, some more than others. The dipole is a low one and probably isn't 72 ohms at the feed point. Mike Scott - AE6WA Tarzana, CA (DM04 / near LA) K3-100 #508/ KX1 #1311 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: k3 SWR readings seem generous
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Mike,
I have to accept your observations, but must ask - have you calibrated the K3 wattmeter? Neglecting to do that can cause the SWR readings to be off by a fair amount. That being said, consider the purpose of the K3 having an SWR indication at all - that is to determine the minimum SWR during a TUNE cycle. The *minimum* SWR is the important parameter to indicate the best tuning point rather than any absolute SWR reading. Long ago when using manual tuners, my elmer told me to simply tune for the lowest reflected power possible, and that was the correct tuning point. The KAT3 tuner algorithm does the same thing - it seeks the minimum reflected power - the absolute SWR is not important, although it may be of interest. Even so, the K3 SWR indication on your K3 does seem to be lower than it should be. Again, if you have not done the Wattmeter Calibration, that would be a step in the right direction. 73, Don W3FPR Mike Scott wrote: > I have been working on antennas today and have a puzzle. I am finding that > the K3 SWR indications are unbelievable generous. > > With my 40M inverted V fed with RG8X (50 ohm) coax I see that the K3 seems > generous in the SWR indication on tune with ATU bypassed. I have noticed a > slight change in SWR with K3 power setting so the following was taken with > K3 tune power set to 100 watts. If I set it to 10 watts the discrepancy is > greater... > SWR SWR SWR > Freq. K3 VA1 Daiwa > 7.00 MHz 1.3 1.92 2.0 > 7.05 MHz 1.2 1.92 1.9 > 7.1 MHz 1.2 1.98 1.95 > 7.15 MHz 1.3 2.26 2.1 > 7.2 MHz 1.9 2.60 2.3 > 7.25 MHz 1.5 2.88 2.6 > 7.3 MHz 1.6 3.32 2.7 > > The Daiwa is the CN-101L cross needle meter. The VA1 is the Autek Rx Vector > antenna analyzer. The VA1 does not have a tuned input so it is possible > that it can be fooled by local broadcast stations. I don't suspect this > issue here as there aren't any close by broadcast stations that I am aware > of. The Daiwa and the VA1 tend to agree pretty well anyway. The K3 > measurements are the outliers. This antenna on a "Tenna Dipper" shows > minimal SWR at 7.040 MHz, just where I tuned it a few years ago. The LED > does not extinguish indicating higher than 1:1 SWR at the minimum. If you > look at the numbers, I guess I don't believe the K3, Do you think my antenna > is below 1.6 to 1 across the entire 40M band? > > > So now on to 20M dipole fed with RG58 (50 Ohm Coax)... > The Tenna Dipper fully extinguishes at 13.805 MHz indicating that my antenna > is bit too long but is close to 1:1 at that frequency. > > Freq K3 VA1 Daiwa > 13.81 -- 1.12 -- > 14.0 MHz 1.1 1.24 1.31 > 14.1 MHz 1.1 1.30 1.70 > 14.2 MHz 1.1 1.55 1.85 > 14.3 MHz 1.2 1.69 1.85 > > RG58 may have some losses on this band so perhaps all of the SWR indications > are generous, some more than others. The dipole is a low one and probably > isn't 72 ohms at the feed point. > > Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: k3 SWR readings seem generous
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In reply to this post by Mike Scott-7
I noticed the same thing. My factory-assembled K3 is reading 1.0 SWR while
my LP-100A and tuner both agree on about 1.4-1.5. Michael - N6MEF ------------------------------ Message: 45 Date: Thu, 1 Jan 2009 17:47:04 -0800 From: "Mike Scott" <[hidden email]> Subject: [Elecraft] k3 SWR readings seem generous To: <[hidden email]> Message-ID: <7A956B0039B848BD89A04D31855C40BB@DBQJ5V71> Content-Type: text/plain; charset="us-ascii" I have been working on antennas today and have a puzzle. I am finding that the K3 SWR indications are unbelievable generous. With my 40M inverted V fed with RG8X (50 ohm) coax I see that the K3 seems generous in the SWR indication on tune with ATU bypassed. I have noticed a slight change in SWR with K3 power setting so the following was taken with K3 tune power set to 100 watts. If I set it to 10 watts the discrepancy is greater... SWR SWR SWR Freq. K3 VA1 Daiwa 7.00 MHz 1.3 1.92 2.0 7.05 MHz 1.2 1.92 1.9 7.1 MHz 1.2 1.98 1.95 7.15 MHz 1.3 2.26 2.1 7.2 MHz 1.9 2.60 2.3 7.25 MHz 1.5 2.88 2.6 7.3 MHz 1.6 3.32 2.7 The Daiwa is the CN-101L cross needle meter. The VA1 is the Autek Rx Vector antenna analyzer. The VA1 does not have a tuned input so it is possible that it can be fooled by local broadcast stations. I don't suspect this issue here as there aren't any close by broadcast stations that I am aware of. The Daiwa and the VA1 tend to agree pretty well anyway. The K3 measurements are the outliers. This antenna on a "Tenna Dipper" shows minimal SWR at 7.040 MHz, just where I tuned it a few years ago. The LED does not extinguish indicating higher than 1:1 SWR at the minimum. If you look at the numbers, I guess I don't believe the K3, Do you think my antenna is below 1.6 to 1 across the entire 40M band? So now on to 20M dipole fed with RG58 (50 Ohm Coax)... The Tenna Dipper fully extinguishes at 13.805 MHz indicating that my antenna is bit too long but is close to 1:1 at that frequency. Freq K3 VA1 Daiwa 13.81 -- 1.12 -- 14.0 MHz 1.1 1.24 1.31 14.1 MHz 1.1 1.30 1.70 14.2 MHz 1.1 1.55 1.85 14.3 MHz 1.2 1.69 1.85 RG58 may have some losses on this band so perhaps all of the SWR indications are generous, some more than others. The dipole is a low one and probably isn't 72 ohms at the feed point. Mike Scott - AE6WA Tarzana, CA (DM04 / near LA) K3-100 #508/ KX1 #1311 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: k3 SWR readings seem generous
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Isn't the LP100A giving you the actual SWR, not the tuned SWR since the
LP100A is getting current samples from the feedline to the antenna and is independent of the K3 tuner. The K3 tuner is making the K3 see 50 ohms. The LP100 is telling you the actual SWR that exists prior to the K3 tuning it to the 50 ohm. I have the LP100 using it with a SteppIR BiggIR vertical and also a Gap Voyager vertical for 160m and 80m. The LP100 reads around 1.04:1 on the SteppIR on 40m as does the K3 (shows 1 bar), which is close to what my old Diamond meter use to read. However, the Gap SWR is around the 2.3:1 range when the K3 (or PW-1 tuner) reads about 1.5:1 or less. I then realized it was showing me the real SWR, not the tuned SWR. I think I am correct in this assumption. John K8WDN -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Michael E Fox (N6MEF) Sent: Friday, January 02, 2009 1:18 AM To: [hidden email] Subject: RE: [Elecraft] k3 SWR readings seem generous I noticed the same thing. My factory-assembled K3 is reading 1.0 SWR while my LP-100A and tuner both agree on about 1.4-1.5. Michael - N6MEF ------------------------------ Message: 45 Date: Thu, 1 Jan 2009 17:47:04 -0800 From: "Mike Scott" <[hidden email]> Subject: [Elecraft] k3 SWR readings seem generous To: <[hidden email]> Message-ID: <7A956B0039B848BD89A04D31855C40BB@DBQJ5V71> Content-Type: text/plain; charset="us-ascii" I have been working on antennas today and have a puzzle. I am finding that the K3 SWR indications are unbelievable generous. With my 40M inverted V fed with RG8X (50 ohm) coax I see that the K3 seems generous in the SWR indication on tune with ATU bypassed. I have noticed a slight change in SWR with K3 power setting so the following was taken with K3 tune power set to 100 watts. If I set it to 10 watts the discrepancy is greater... SWR SWR SWR Freq. K3 VA1 Daiwa 7.00 MHz 1.3 1.92 2.0 7.05 MHz 1.2 1.92 1.9 7.1 MHz 1.2 1.98 1.95 7.15 MHz 1.3 2.26 2.1 7.2 MHz 1.9 2.60 2.3 7.25 MHz 1.5 2.88 2.6 7.3 MHz 1.6 3.32 2.7 The Daiwa is the CN-101L cross needle meter. The VA1 is the Autek Rx Vector antenna analyzer. The VA1 does not have a tuned input so it is possible that it can be fooled by local broadcast stations. I don't suspect this issue here as there aren't any close by broadcast stations that I am aware of. The Daiwa and the VA1 tend to agree pretty well anyway. The K3 measurements are the outliers. This antenna on a "Tenna Dipper" shows minimal SWR at 7.040 MHz, just where I tuned it a few years ago. The LED does not extinguish indicating higher than 1:1 SWR at the minimum. If you look at the numbers, I guess I don't believe the K3, Do you think my antenna is below 1.6 to 1 across the entire 40M band? So now on to 20M dipole fed with RG58 (50 Ohm Coax)... The Tenna Dipper fully extinguishes at 13.805 MHz indicating that my antenna is bit too long but is close to 1:1 at that frequency. Freq K3 VA1 Daiwa 13.81 -- 1.12 -- 14.0 MHz 1.1 1.24 1.31 14.1 MHz 1.1 1.30 1.70 14.2 MHz 1.1 1.55 1.85 14.3 MHz 1.2 1.69 1.85 RG58 may have some losses on this band so perhaps all of the SWR indications are generous, some more than others. The dipole is a low one and probably isn't 72 ohms at the feed point. Mike Scott - AE6WA Tarzana, CA (DM04 / near LA) K3-100 #508/ KX1 #1311 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: k3 SWR readings seem generous
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I forgot to mention. I do not use the ATU on my K3 on 40m since I have the
SteppIR BiggIR vertical, and the K3 SWR reading shows only 1 bar which tells me it is seeing 1:1 SWR which is close to the LPA100 reading of 1.04:1. The LP100 just shows the unvarnished truth sometimes about the actual antenna resonance. It is a great tool. John K8WDN -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of John Gaynard Sent: Friday, January 02, 2009 2:24 AM To: 'Michael E Fox (N6MEF)'; [hidden email] Subject: RE: [Elecraft] k3 SWR readings seem generous Isn't the LP100A giving you the actual SWR, not the tuned SWR since the LP100A is getting current samples from the feedline to the antenna and is independent of the K3 tuner. The K3 tuner is making the K3 see 50 ohms. The LP100 is telling you the actual SWR that exists prior to the K3 tuning it to the 50 ohm. I have the LP100 using it with a SteppIR BiggIR vertical and also a Gap Voyager vertical for 160m and 80m. The LP100 reads around 1.04:1 on the SteppIR on 40m as does the K3 (shows 1 bar), which is close to what my old Diamond meter use to read. However, the Gap SWR is around the 2.3:1 range when the K3 (or PW-1 tuner) reads about 1.5:1 or less. I then realized it was showing me the real SWR, not the tuned SWR. I think I am correct in this assumption. John K8WDN -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Michael E Fox (N6MEF) Sent: Friday, January 02, 2009 1:18 AM To: [hidden email] Subject: RE: [Elecraft] k3 SWR readings seem generous I noticed the same thing. My factory-assembled K3 is reading 1.0 SWR while my LP-100A and tuner both agree on about 1.4-1.5. Michael - N6MEF ------------------------------ Message: 45 Date: Thu, 1 Jan 2009 17:47:04 -0800 From: "Mike Scott" <[hidden email]> Subject: [Elecraft] k3 SWR readings seem generous To: <[hidden email]> Message-ID: <7A956B0039B848BD89A04D31855C40BB@DBQJ5V71> Content-Type: text/plain; charset="us-ascii" I have been working on antennas today and have a puzzle. I am finding that the K3 SWR indications are unbelievable generous. With my 40M inverted V fed with RG8X (50 ohm) coax I see that the K3 seems generous in the SWR indication on tune with ATU bypassed. I have noticed a slight change in SWR with K3 power setting so the following was taken with K3 tune power set to 100 watts. If I set it to 10 watts the discrepancy is greater... SWR SWR SWR Freq. K3 VA1 Daiwa 7.00 MHz 1.3 1.92 2.0 7.05 MHz 1.2 1.92 1.9 7.1 MHz 1.2 1.98 1.95 7.15 MHz 1.3 2.26 2.1 7.2 MHz 1.9 2.60 2.3 7.25 MHz 1.5 2.88 2.6 7.3 MHz 1.6 3.32 2.7 The Daiwa is the CN-101L cross needle meter. The VA1 is the Autek Rx Vector antenna analyzer. The VA1 does not have a tuned input so it is possible that it can be fooled by local broadcast stations. I don't suspect this issue here as there aren't any close by broadcast stations that I am aware of. The Daiwa and the VA1 tend to agree pretty well anyway. The K3 measurements are the outliers. This antenna on a "Tenna Dipper" shows minimal SWR at 7.040 MHz, just where I tuned it a few years ago. The LED does not extinguish indicating higher than 1:1 SWR at the minimum. If you look at the numbers, I guess I don't believe the K3, Do you think my antenna is below 1.6 to 1 across the entire 40M band? So now on to 20M dipole fed with RG58 (50 Ohm Coax)... The Tenna Dipper fully extinguishes at 13.805 MHz indicating that my antenna is bit too long but is close to 1:1 at that frequency. Freq K3 VA1 Daiwa 13.81 -- 1.12 -- 14.0 MHz 1.1 1.24 1.31 14.1 MHz 1.1 1.30 1.70 14.2 MHz 1.1 1.55 1.85 14.3 MHz 1.2 1.69 1.85 RG58 may have some losses on this band so perhaps all of the SWR indications are generous, some more than others. The dipole is a low one and probably isn't 72 ohms at the feed point. Mike Scott - AE6WA Tarzana, CA (DM04 / near LA) K3-100 #508/ KX1 #1311 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: k3 SWR readings seem generous
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In reply to this post by Mike Scott-7
This thread came at the right time. I have just finished
re-calibrating my LP-100A. I did this after having used the unit for 6 months, however the calibration was very close to the original settings. Then I thought that I would check my K3 SWR indication. The results are not as good as I would expect. I set the K3 with a tune power of 10W, representing the level of power one might use to adjust an ATU. The measurements I made were using 2 x 8 inch lengths of RG8U from the K3 into the LP-100A coupler, and then from the coupler into the dummy load. The dummy load is a precision 100W one which I measured with a VNA and has a VSWR of <1.03 from 1 to 30 Mhz. To simulate a 2:1 VSWR I used another dummy load (not quite as good) in parallel. The K3 output was from ANT1 using the internal ATU. The ATU was automatically tuned to 1:1 on all bands. The results I got for 2:1 VSWR are as follows:- LP-100 K3 160 1.99 1.8 80 1.99 1.8 60 1.99 1.8 40 1.95 1.8 30 1.97 1.6 20 1.97 1.4 17 1.97 1.3 15 1.96 1.2 12 1.96 1.5 10 1.96 1.4 As can be seen my K3 SWR indication constantly under reads. However, it really gets bad on 20,17 & 15. I will be interested in the results of others conducting similar tests. 73 Stewart G3RXQ On Thu, 1 Jan 2009 17:47:04 -0800, Mike Scott wrote: > I have been working on antennas today and have a puzzle. I am finding that > the K3 SWR indications are unbelievable generous. > > With my 40M inverted V fed with RG8X (50 ohm) coax I see that the K3 seems > generous in the SWR indication on tune with ATU bypassed. I have noticed a > slight change in SWR with K3 power setting so the following was taken with > K3 tune power set to 100 watts. If I set it to 10 watts the discrepancy is > greater... > SWR SWR SWR > Freq. K3 VA1 Daiwa > 7.00 MHz 1.3 1.92 2.0 > 7.05 MHz 1.2 1.92 1.9 > 7.1 MHz 1.2 1.98 1.95 > 7.15 MHz 1.3 2.26 2.1 > 7.2 MHz 1.9 2.60 2.3 > 7.25 MHz 1.5 2.88 2.6 > 7.3 MHz 1.6 3.32 2.7 > > The Daiwa is the CN-101L cross needle meter. The VA1 is the > antenna analyzer. The VA1 does not have a tuned input so it is possible > that it can be fooled by local broadcast stations. I don't suspect this > issue here as there aren't any close by broadcast stations that I am aware > of. The Daiwa and the VA1 tend to agree pretty well anyway. The K3 > measurements are the outliers. This antenna on a "Tenna Dipper" shows > minimal SWR at 7.040 MHz, just where I tuned it a few years ago. The LED > does not extinguish indicating higher than 1:1 SWR at the minimum. If you > look at the numbers, I guess I don't believe the K3, Do you think my antenna > is below 1.6 to 1 across the entire 40M band? > > > So now on to 20M dipole fed with RG58 (50 Ohm Coax)... > The Tenna Dipper fully extinguishes at 13.805 MHz indicating that my antenna > is bit too long but is close to 1:1 at that frequency. > > Freq K3 VA1 Daiwa > 13.81 -- 1.12 -- > 14.0 MHz 1.1 1.24 1.31 > 14.1 MHz 1.1 1.30 1.70 > 14.2 MHz 1.1 1.55 1.85 > 14.3 MHz 1.2 1.69 1.85 > > RG58 may have some losses on this band so perhaps all of the SWR > are generous, some more than others. The dipole is a low one and probably > isn't 72 ohms at the feed point. > > Mike Scott - AE6WA > Tarzana, CA (DM04 / near LA) > K3-100 #508/ KX1 #1311 > > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: k3 SWR readings seem generous
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In reply to this post by Mike Scott-7
>However, the Gap SWR is around the >2.3:1 range when the K3 (or PW-1 tuner) reads about 1.5:1 or less. I then >realized it was showing me the real SWR, not the tuned SWR. >I think I am correct in this assumption. John, your understanding is correct unless the K3 ATU is in bypass mode which it was for my tests. The K3 then should be measuring the feed line SWR because there is no tuner in the circuit. Also I used tune mode which shows the digital readout of SWR, not the number of bars on the SWR readout. So try it with the K3 tuner bypassed and see what you get. Mike Scott - AE6WA Tarzana, CA (DM04 / near LA) K3-100 #508/ KX1 #1311 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
RE: k3 SWR readings seem generous
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In reply to this post by John Gaynard
I don't think so.
The K3 tuner is in bypass. The LP-100A is next in line, followed by the tuner (no amp yet) followed by the fan dipole. The tuner is showing the tuned SWR. The LP-100A sees only the tuned SWR and the K3 tuner is off so it should see the same thing that the LP-100A sees. The LP-100A and the tuner generally agree (the LP-100A is digital and the tuner uses crossed-needles, but it's close). The K3 is consistently lower. 73, Michael / N6MEF -----Original Message----- From: John Gaynard [mailto:[hidden email]] Sent: Thursday, January 01, 2009 11:24 PM To: 'Michael E Fox (N6MEF)'; [hidden email] Subject: RE: [Elecraft] k3 SWR readings seem generous Isn't the LP100A giving you the actual SWR, not the tuned SWR since the LP100A is getting current samples from the feedline to the antenna and is independent of the K3 tuner. The K3 tuner is making the K3 see 50 ohms. The LP100 is telling you the actual SWR that exists prior to the K3 tuning it to the 50 ohm. I have the LP100 using it with a SteppIR BiggIR vertical and also a Gap Voyager vertical for 160m and 80m. The LP100 reads around 1.04:1 on the SteppIR on 40m as does the K3 (shows 1 bar), which is close to what my old Diamond meter use to read. However, the Gap SWR is around the 2.3:1 range when the K3 (or PW-1 tuner) reads about 1.5:1 or less. I then realized it was showing me the real SWR, not the tuned SWR. I think I am correct in this assumption. John K8WDN -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Michael E Fox (N6MEF) Sent: Friday, January 02, 2009 1:18 AM To: [hidden email] Subject: RE: [Elecraft] k3 SWR readings seem generous I noticed the same thing. My factory-assembled K3 is reading 1.0 SWR while my LP-100A and tuner both agree on about 1.4-1.5. Michael - N6MEF ------------------------------ Message: 45 Date: Thu, 1 Jan 2009 17:47:04 -0800 From: "Mike Scott" <[hidden email]> Subject: [Elecraft] k3 SWR readings seem generous To: <[hidden email]> Message-ID: <7A956B0039B848BD89A04D31855C40BB@DBQJ5V71> Content-Type: text/plain; charset="us-ascii" I have been working on antennas today and have a puzzle. I am finding that the K3 SWR indications are unbelievable generous. With my 40M inverted V fed with RG8X (50 ohm) coax I see that the K3 seems generous in the SWR indication on tune with ATU bypassed. I have noticed a slight change in SWR with K3 power setting so the following was taken with K3 tune power set to 100 watts. If I set it to 10 watts the discrepancy is greater... SWR SWR SWR Freq. K3 VA1 Daiwa 7.00 MHz 1.3 1.92 2.0 7.05 MHz 1.2 1.92 1.9 7.1 MHz 1.2 1.98 1.95 7.15 MHz 1.3 2.26 2.1 7.2 MHz 1.9 2.60 2.3 7.25 MHz 1.5 2.88 2.6 7.3 MHz 1.6 3.32 2.7 The Daiwa is the CN-101L cross needle meter. The VA1 is the Autek Rx Vector antenna analyzer. The VA1 does not have a tuned input so it is possible that it can be fooled by local broadcast stations. I don't suspect this issue here as there aren't any close by broadcast stations that I am aware of. The Daiwa and the VA1 tend to agree pretty well anyway. The K3 measurements are the outliers. This antenna on a "Tenna Dipper" shows minimal SWR at 7.040 MHz, just where I tuned it a few years ago. The LED does not extinguish indicating higher than 1:1 SWR at the minimum. If you look at the numbers, I guess I don't believe the K3, Do you think my antenna is below 1.6 to 1 across the entire 40M band? So now on to 20M dipole fed with RG58 (50 Ohm Coax)... The Tenna Dipper fully extinguishes at 13.805 MHz indicating that my antenna is bit too long but is close to 1:1 at that frequency. Freq K3 VA1 Daiwa 13.81 -- 1.12 -- 14.0 MHz 1.1 1.24 1.31 14.1 MHz 1.1 1.30 1.70 14.2 MHz 1.1 1.55 1.85 14.3 MHz 1.2 1.69 1.85 RG58 may have some losses on this band so perhaps all of the SWR indications are generous, some more than others. The dipole is a low one and probably isn't 72 ohms at the feed point. Mike Scott - AE6WA Tarzana, CA (DM04 / near LA) K3-100 #508/ KX1 #1311 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: k3 SWR readings seem generous
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In reply to this post by Michael Fox - N6MEF
Michael E Fox (N6MEF) wrote:
> My factory-assembled K3 is reading 1.0 SWR while my LP-100A and tuner > both agree on about 1.4-1.5. The KAT3's stray impedance (in bypass mode) may impact the SWR as seen by the K3's bridge, since this bridge is between the ATU and the LPFs. This effect would be more pronounced on the highest bands. Your external bridge is between the KAT3 and the antenna, so it may read differently from the K3 if any strays are present. The "bypassed" state of the KAT3 is actually a per-band combination of L and C intended to cancel out the ATU's own strays. But compensation accuracy will vary from one KAT3 to the next due to the 5% tolerance on the components. So on some bands, the SWR in bypass mode might actually look closer to 1.0:1 with a load Z that is not quite perfect. Still, all of these effects should be small, and I'll do some tests to see if I can duplicate an SWR discrepancy between the K3 and an external instrument. 73, Wayne N6KR --- http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: k3 SWR readings seem generous
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In reply to this post by Stewart Baker
Stewart Baker wrote:
> The K3 output was from ANT1 using the internal ATU. The ATU was > automatically tuned to 1:1 on all bands. > The results I got for 2:1 VSWR are as follows:- > > LP-100 K3 > 160 1.99 1.8 > 80 1.99 1.8 > 60 1.99 1.8 > 40 1.95 1.8 > 30 1.97 1.6 > 20 1.97 1.4 > 17 1.97 1.3 > 15 1.96 1.2 > 12 1.96 1.5 > 10 1.96 1.4 Much of this could be attributed to the different locations of the two bridges (see my previous email). Strays will vary from band to band. Also, the K3's bridge will be a little more accurate at 100 W than at 10 W due to the bridge diode drops. I compensate for this to some degree in firmware, and I'll review it when I get a chance. 73, Wayne N6KR --- http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: k3 SWR readings seem generous
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No problem Wayne.
I always use 5W, and the LP-100A when I tune up my external ATU. 73 Stewart G3RXQ On Fri, 2 Jan 2009 10:01:08 -0800, wayne burdick wrote: > Stewart Baker wrote: > >> The K3 output was from ANT1 using the internal ATU. The ATU was >> automatically tuned to 1:1 on all bands. >> The results I got for 2:1 VSWR are as follows:- >> >> LP-100 K3 >> 160 1.99 1.8 >> 80 1.99 1.8 >> 60 1.99 1.8 >> 40 1.95 1.8 >> 30 1.97 1.6 >> 20 1.97 1.4 >> 17 1.97 1.3 >> 15 1.96 1.2 >> 12 1.96 1.5 >> 10 1.96 1.4 > > Much of this could be attributed to the different locations of > bridges (see my previous email). Strays will vary from band to band. > > Also, the K3's bridge will be a little more accurate at 100 W than at > 10 W due to the bridge diode drops. I compensate for this to some > degree in firmware, and I'll review it when I get a chance. > > 73, > Wayne > N6KR > > --- > > http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by wayne burdick
"I always use 5W, ... when I tune up my external ATU."
Actually, I use 15 watts for tuning both the internal K3 tuner, as well as my external MFJ-998 tuner. I do this for two reasons: 1) I get much better SWR agreement between 15 watts and full power than I do with 5 watts and full power, especially on the external tuner. 2) I figure that using a switching-type tuner stresses the 10-watt output circuitry of the K3 at 5-watts tune power (all that hot-switching). But at 15 watts, the K3 100 watt PA should have plenty of margin. It might be interesting to know what power levels Elecraft recommends regarding radio stress during tuning. Phil - AD5X _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Re: k3 SWR readings seem generous
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In reply to this post by wayne burdick
One thing I think would be really slick is to see a path in which
someone can insert a watt meter such as the LP-100 into the chain between the output and the antenna tuner where it belongs. I really like all of the flexibility that the RX ANT path affords... Would be really neat to be able to see something like that on the way out. ~Brett (KC7OTG) On Fri, 2009-01-02 at 10:01 -0800, wayne burdick wrote: > Stewart Baker wrote: > > > The K3 output was from ANT1 using the internal ATU. The ATU was > > automatically tuned to 1:1 on all bands. > > The results I got for 2:1 VSWR are as follows:- > > > > LP-100 K3 > > 160 1.99 1.8 > > 80 1.99 1.8 > > 60 1.99 1.8 > > 40 1.95 1.8 > > 30 1.97 1.6 > > 20 1.97 1.4 > > 17 1.97 1.3 > > 15 1.96 1.2 > > 12 1.96 1.5 > > 10 1.96 1.4 > > Much of this could be attributed to the different locations of the two > bridges (see my previous email). Strays will vary from band to band. > > Also, the K3's bridge will be a little more accurate at 100 W than at > 10 W due to the bridge diode drops. I compensate for this to some > degree in firmware, and I'll review it when I get a chance. > > 73, > Wayne > N6KR > > --- > > http://www.elecraft.com > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Re: k3 SWR readings seem generous
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In reply to this post by Phil Salas
On Sat, 3 Jan 2009 07:34:13 -0600, Phil & Debbie Salas wrote:
> "I always use 5W, ... when I tune up my external ATU." > > Actually, I use 15 watts for tuning both the internal K3 tuner, as well as > my external MFJ-998 tuner. I do this for two reasons: > > 1) I get much better SWR agreement between 15 watts and full power than I > do with 5 watts and full power, especially on the external tuner. > > 2) I figure that using a switching-type tuner stresses the 10-watt output > circuitry of the K3 at 5-watts tune power (all that hot-switching). But at > 15 watts, the K3 100 watt PA should have plenty of margin. > > It might be interesting to know what power levels Elecraft recommends > regarding radio stress during tuning. > > Phil - AD5X > With my setup. a) I use 5W which gives an accurate VSWR reading on the LP-100A. b) A power level of 5W keeps the potential QRM level to a minimum. Of course radiating no tune up power would be best. c) I am sure that the K3 10W PA would stand 5W for a 30 second tune.. d) I pre-tune my homebrew fully balanced ATU prior to pressing the TUNE button. No live RF switching is involved. Hot switching RF in an external ATU is not to be recommended for any radio at any level. Stewart G3RXQ > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Phil Salas
"Hot switching RF in an external ATU is not to be recommended for
any radio at any level." BUT - you DO hot-switch your K3's RF output when using any relay-based auto-tuner, including the internal K3 auto-tuner. So my reasoning is that I'd rather hot-switch the 100-watt PA at 15 watts rather than the 10-watt PA at 5 watts. And then, my MFJ-998 (which I use with my ALS-600) reads SWR more accurately at 15 watts than it does at 5 watts, so when I go to full power the tuned SWR is still minimum. As Wayne stated earlier, SWR readings at low power may be less accurate due to the detector diode voltage drop at low power. Phil - AD5X _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Re: k3 SWR readings seem generous
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On Sat, 3 Jan 2009 08:58:57 -0600, Phil & Debbie Salas wrote:
> "Hot switching RF in an external ATU is not to be recommended for > any radio at any level." > > BUT - you DO hot-switch your K3's RF output when using any relay-based > auto-tuner, including the internal K3 auto-tuner. So my reasoning is that > I'd rather hot-switch the 100-watt PA at 15 watts rather than the 10-watt PA > at 5 watts. And then, my MFJ-998 (which I use with my ALS-600) reads SWR > more accurately at 15 watts than it does at 5 watts, so when I go to full > power the tuned SWR is still minimum. As Wayne stated earlier, SWR readings > at low power may be less accurate due to the detector diode voltage drop at > low power. > > Phil - AD5X > OK, to be strictly accurate...... "Hot switching RF in an external ATU (other than auto-tuners designed to be operated that way) is not to be recommended for any radio at any level." I am sure that the *internal* K3 ATU has been designed to perform its tuning function at a safe power level, whatever output power level the operator selects. Using the LP-100A I am avoiding (for the present) the influence detector diode volts drops vs power have on my SWR measurements. Stewart G3RXQ > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Re: Re: k3 SWR readings seem generous
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In reply to this post by Phil Salas
Phil,
There is a huge electrical difference between switching an additional inductor in series with the load (or a capacitor in parallel) than what is commonly seen as "hot-switching" which results in the amplifier seeing an open circuit until the relay closes. A very high RF voltage will exist if the PA is operated into an open circuit. During the tuner's tune cycle, the load is never open circuit to the PA, and the resulting RF voltage is kept under control. 73, Don W3FPR Phil & Debbie Salas wrote: > "Hot switching RF in an external ATU is not to be recommended for > any radio at any level." > > BUT - you DO hot-switch your K3's RF output when using any relay-based > auto-tuner, including the internal K3 auto-tuner. So my reasoning is > that I'd rather hot-switch the 100-watt PA at 15 watts rather than the > 10-watt PA at 5 watts. And then, my MFJ-998 (which I use with my > ALS-600) reads SWR more accurately at 15 watts than it does at 5 > watts, so when I go to full power the tuned SWR is still minimum. As > Wayne stated earlier, SWR readings at low power may be less accurate > due to the detector diode voltage drop at low power. > > Phil - AD5X > Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Phil Salas
"There is a huge electrical difference between switching an additional
inductor in series with the load (or a capacitor in parallel) than what is commonly seen as "hot-switching" which results in the amplifier seeing an open circuit until the relay closes. A very high RF voltage will exist if the PA is operated into an open circuit. During the tuner's tune cycle, the load is never open circuit to the PA, and the resulting RF voltage is kept under control." Don - Maybe my "hot switch" term was not accurate for this situation. I think of hot switching as making sudden abrupt impedance changes at the output of your radio or amplifier. In any case, it seems to me that it would be less hard on the radio if you do this at 15 watts on a 100 watt PA vs 5 watts on a 10 watt PA. But then, I could be wrong. Phil - AD5X _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Brett Howard
Brett, this is something I would love to see in all rigs and amplifiers, but then I'm prejudiced;-)
73, Larry N8LP <quote author="Brett Howard"> One thing I think would be really slick is to see a path in which someone can insert a watt meter such as the LP-100 into the chain between the output and the antenna tuner where it belongs. I really like all of the flexibility that the RX ANT path affords... Would be really neat to be able to see something like that on the way out. ~Brett (KC7OTG) |
Re: Re: k3 SWR readings seem generous
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In reply to this post by Phil Salas
Phil,
It is perfectly OK to do that, but I believe you are being more conservative than necessary. The KAT3 is designed to 'take it' and the PAs of the K3 (either high power or low power) are also - if that were not the case, there would be a big warning statement in the manual. In general, Elecraft designs are on the conservative side and will withstand normal operating without stress. 73, Don W3FPR Phil & Debbie Salas wrote: > "There is a huge electrical difference between switching an additional > inductor in series with the load (or a capacitor in parallel) than what > is commonly seen as "hot-switching" which results in the amplifier > seeing an open circuit until the relay closes. A very high RF voltage > will exist if the PA is operated into an open circuit. > During the tuner's tune cycle, the load is never open circuit to the PA, > and the resulting RF voltage is kept under control." > > Don - Maybe my "hot switch" term was not accurate for this situation. > I think of hot switching as making sudden abrupt impedance changes at > the output of your radio or amplifier. In any case, it seems to me > that it would be less hard on the radio if you do this at 15 watts on > a 100 watt PA vs 5 watts on a 10 watt PA. But then, I could be wrong. > > Phil - AD5X > Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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