Re: [Elecraft] Internal K3 SWR vs Extermal SWR Meter
I gave up a long time ago as to precision and accuracy (two different animals) for SWR indicators. First of all there is only one connection sequence - xmtr, SWR meter, tuner. Any other order, or anything else in line, will confuse and obfuscate. Ones that I have enjoyed using are the cross-needle styles, but with built-in tuners, they're useless. In the 53 years I have been a ham, the old rule still applies - tune for maximum smoke! Don't sweat the small details. Just do it and have fun. 73,72 Neal WA6OCP From: Mel Farrer To: ab2tc ; "elecraft@mailman.qth.net" Sent: Thursday, November 21, 2013 2:13 PM Subject: Re: [Elecraft] Internal K3 SWR vs Extermal SWR Meter In an older era, Telonic and HP made Rho-tectors as I remember. The beauty of these was the components of the bridge were precision, that is the resistors were matched on one side and the diode compensated for linearity. No transformer. There were 4 ports. One port had the precision reference 50 termination, the opposite side had the DUT, the third port was RF, and the last port the DC signal output. The sweeper was fed into the RF port and the DC to the vertical channel of a scope, the swept voltage went to the horizontal channel. If handled properly they are good from 1 to 1500 MHz. It is easy to see 3 to 30 MHz for checking a cable. Depending on the sweeper, accuracy could be easily calibrated with 25, 50, 75, and 100 ohm precision loads. 1.5:1 would give you 2 cms of deflection. I have a home brew one and it is my SWR reference to check the portable measurement device. No it doesn't give you R and j, sorry. Mel, K6KBE On Thursday, November 21, 2013 1:22 PM, ab2tc wrote: Hi, I am not aware of any "Wattmeters/SWR Bridges" that work by reading E and estimating power as (E^2)/50 ohm. If it did, it would not be able to determine any kind of estimate of SWR or reflected power. All the "Wattmeters/SWR Bridges" I am aware of are constructed with a bridge circuit that is in principle capable of correctly displaying forward and reflected power even with a complex load impedance. But they do rely on the performance of at least one transformer, often a capacitive divider for sensing voltage and diode rectifiers with their inherent non-linearities, especially at the low power levels preferred for tune-ups. These components are often chosen for their lowest cost rather than performance and calibration may be sloppy. Even with quality RF components, unless the device has a microcontroller that can store and apply corrections for frequency, power level and temperature, accuracy is generally poor, easily exceeding 5-10% of full scale. High end devices that do much better than that are available but they come at a cost. Nothing in the instrument can compensate for the errors caused by common mode currents in the coax though so it's always important to keep the RF out of the shack. Three instruments in a line next to each other *should* read the same forward, reflected power and SWR under ideal conditions. AB2TC - Knut k6dgw wrote > Most ham-grade "Wattmeters/SWR Bridges" that I've encountered read E, > assume R, and "calculate" P in an analog fashion. When SWR is not 1:1, > Z is not equal to 50 ohms, and in most cases, the higher the SWR, the > higher the power indicated on the meter. For these instruments, nothing > you see on the indicator is true unless the SWR is 1:1 [i.e. the > impedance is 50 ohms]. Even then, many are sensitive to common-mode > current on the outside of the coax shield, and most of us have *some* > common-mode conduction on our feedlines. > > I once put three ham-grade "wattmeters" in series right next to each > other on 20m, and they all read differently. When I changed their order > in the feedline, they all read differently ... and different from what > they had before. I concluded that, unless I was willing to spend the > money to acquire test equipment that actually sensed and displayed watts > and not E^2/R, I'd have to be satisfied with approximations. > > 73, > > Fred K6DGW > - Northern California Contest Club > - CU in the 2014 Cal QSO Party 4-5 Oct 2014 > - http://www.cqp.org/ > -- View this message in context: http://elecraft.365791.n2.nabble.com/Internal-K3-SWR-vs-Extermal-SWR-Meter-tp7580938p7581035.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __
Re: [Elecraft] Internal K3 SWR vs Extermal SWR Meter
In an older era, Telonic and HP made Rho-tectors as I remember. The beauty of these was the components of the bridge were precision, that is the resistors were matched on one side and the diode compensated for linearity. No transformer. There were 4 ports. One port had the precision reference 50 termination, the opposite side had the DUT, the third port was RF, and the last port the DC signal output. The sweeper was fed into the RF port and the DC to the vertical channel of a scope, the swept voltage went to the horizontal channel. If handled properly they are good from 1 to 1500 MHz. It is easy to see 3 to 30 MHz for checking a cable. Depending on the sweeper, accuracy could be easily calibrated with 25, 50, 75, and 100 ohm precision loads. 1.5:1 would give you 2 cms of deflection. I have a home brew one and it is my SWR reference to check the portable measurement device. No it doesn't give you R and j, sorry. Mel, K6KBE On Thursday, November 21, 2013 1:22 PM, ab2tc wrote: Hi, I am not aware of any "Wattmeters/SWR Bridges" that work by reading E and estimating power as (E^2)/50 ohm. If it did, it would not be able to determine any kind of estimate of SWR or reflected power. All the "Wattmeters/SWR Bridges" I am aware of are constructed with a bridge circuit that is in principle capable of correctly displaying forward and reflected power even with a complex load impedance. But they do rely on the performance of at least one transformer, often a capacitive divider for sensing voltage and diode rectifiers with their inherent non-linearities, especially at the low power levels preferred for tune-ups. These components are often chosen for their lowest cost rather than performance and calibration may be sloppy. Even with quality RF components, unless the device has a microcontroller that can store and apply corrections for frequency, power level and temperature, accuracy is generally poor, easily exceeding 5-10% of full scale. High end devices that do much better than that are available but they come at a cost. Nothing in the instrument can compensate for the errors caused by common mode currents in the coax though so it's always important to keep the RF out of the shack. Three instruments in a line next to each other *should* read the same forward, reflected power and SWR under ideal conditions. AB2TC - Knut k6dgw wrote > Most ham-grade "Wattmeters/SWR Bridges" that I've encountered read E, > assume R, and "calculate" P in an analog fashion. When SWR is not 1:1, > Z is not equal to 50 ohms, and in most cases, the higher the SWR, the > higher the power indicated on the meter. For these instruments, nothing > you see on the indicator is true unless the SWR is 1:1 [i.e. the > impedance is 50 ohms]. Even then, many are sensitive to common-mode > current on the outside of the coax shield, and most of us have *some* > common-mode conduction on our feedlines. > > I once put three ham-grade "wattmeters" in series right next to each > other on 20m, and they all read differently. When I changed their order > in the feedline, they all read differently ... and different from what > they had before. I concluded that, unless I was willing to spend the > money to acquire test equipment that actually sensed and displayed watts > and not E^2/R, I'd have to be satisfied with approximations. > > 73, > > Fred K6DGW > - Northern California Contest Club > - CU in the 2014 Cal QSO Party 4-5 Oct 2014 > - www.cqp.org > -- View this message in context: http://elecraft.365791.n2.nabble.com/Internal-K3-SWR-vs-Extermal-SWR-Meter-tp7580938p7581035.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html __ 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] Internal K3 SWR vs Extermal SWR Meter
Hi, I am not aware of any "Wattmeters/SWR Bridges" that work by reading E and estimating power as (E^2)/50 ohm. If it did, it would not be able to determine any kind of estimate of SWR or reflected power. All the "Wattmeters/SWR Bridges" I am aware of are constructed with a bridge circuit that is in principle capable of correctly displaying forward and reflected power even with a complex load impedance. But they do rely on the performance of at least one transformer, often a capacitive divider for sensing voltage and diode rectifiers with their inherent non-linearities, especially at the low power levels preferred for tune-ups. These components are often chosen for their lowest cost rather than performance and calibration may be sloppy. Even with quality RF components, unless the device has a microcontroller that can store and apply corrections for frequency, power level and temperature, accuracy is generally poor, easily exceeding 5-10% of full scale. High end devices that do much better than that are available but they come at a cost. Nothing in the instrument can compensate for the errors caused by common mode currents in the coax though so it's always important to keep the RF out of the shack. Three instruments in a line next to each other *should* read the same forward, reflected power and SWR under ideal conditions. AB2TC - Knut k6dgw wrote > Most ham-grade "Wattmeters/SWR Bridges" that I've encountered read E, > assume R, and "calculate" P in an analog fashion. When SWR is not 1:1, > Z is not equal to 50 ohms, and in most cases, the higher the SWR, the > higher the power indicated on the meter. For these instruments, nothing > you see on the indicator is true unless the SWR is 1:1 [i.e. the > impedance is 50 ohms]. Even then, many are sensitive to common-mode > current on the outside of the coax shield, and most of us have *some* > common-mode conduction on our feedlines. > > I once put three ham-grade "wattmeters" in series right next to each > other on 20m, and they all read differently. When I changed their order > in the feedline, they all read differently ... and different from what > they had before. I concluded that, unless I was willing to spend the > money to acquire test equipment that actually sensed and displayed watts > and not E^2/R, I'd have to be satisfied with approximations. > > 73, > > Fred K6DGW > - Northern California Contest Club > - CU in the 2014 Cal QSO Party 4-5 Oct 2014 > - www.cqp.org > -- View this message in context: http://elecraft.365791.n2.nabble.com/Internal-K3-SWR-vs-Extermal-SWR-Meter-tp7580938p7581035.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] Internal K3 SWR vs Extermal SWR Meter
Most ham-grade "Wattmeters/SWR Bridges" that I've encountered read E, assume R, and "calculate" P in an analog fashion. When SWR is not 1:1, Z is not equal to 50 ohms, and in most cases, the higher the SWR, the higher the power indicated on the meter. For these instruments, nothing you see on the indicator is true unless the SWR is 1:1 [i.e. the impedance is 50 ohms]. Even then, many are sensitive to common-mode current on the outside of the coax shield, and most of us have *some* common-mode conduction on our feedlines. I once put three ham-grade "wattmeters" in series right next to each other on 20m, and they all read differently. When I changed their order in the feedline, they all read differently ... and different from what they had before. I concluded that, unless I was willing to spend the money to acquire test equipment that actually sensed and displayed watts and not E^2/R, I'd have to be satisfied with approximations. 73, Fred K6DGW - Northern California Contest Club - CU in the 2014 Cal QSO Party 4-5 Oct 2014 - www.cqp.org On 11/17/2013 2:25 PM, Don Wilhelm wrote: In addition, many wattmeters are woefully inaccurate when reading SWR. Most All will be quite accurate for an SWR of 1.0, but at anything other than that, you will find a variation in the readings on amateur grade wattmeters. __ 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] Internal K3 SWR vs Extermal SWR Meter
Mark, the numbers you quoted look pretty typical for SWR meters. They are *not* precision instruments, nor do they need to be even in commercial applications. Within the range of error you reported, there will be no difference in how your K3 and antenna work. Power measurements are no better. Even a much-admired Bird wattmeter with freshly calibrated slugs can be off by 20% or more, depending upon several factors, and I've not seen a freshly calibrated slug since the last time I worked in a laboratory. So it's just as likely the difference you see is the result of external wattmeter calibration as it is the K3's wattmeter calibration. Any procedure for "synching" them is just as likely to make one of them less accurate that it is now. I presume that you are using a good 50 ohm dummy load to compare readings with the KAT3 in bypass, and that you have run the wattmeter calibration procedure in the K3 Owner's manual. 73, Ron AC7AC -Original Message- John, the problem is that I don't have one of these. But thanks for the suggestion. One thing I have not tried is hooking up my antenna and external wattmeter coupler with Antenna 2 instead of Antenna 1. I am anxious to find out if I get the same readings with #2 as I did with #1. I guess I am rather perplexed at the thought that there is such a variance between the K3 wattmeter vs an external wattmeter. Especially, when I connected the coupler to the antenna #1 with a plug and then attached the antenna coax to the coupler. It's a shame that the K3 does not have a way of synching up the internal wattmeter with an external wattmeter. Hopefully somebody from elecraft will read this email and make a comment on it. Thanks to all with their responses. Mark Griffin, KB3Z __ __ 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] Internal K3 SWR vs Extermal SWR Meter
Mark, There is good reason (assuming the internal tuner in the K3) for *not* syncing the wattmeters. With the KAT3 in-line, the SWR is *not* reading the SWR on the feedline, but instead telling you the SWR at the *input* to the KAT3 - that is the load that the K3 PA sees, and that is what really matters for full power output. Remember too that the KAT3 will have some residual reactance even in bypass mode. That will also make a difference in the SWR seen by the K3 PA transistors and the SWR on the feedline - it is just one of "those things". A 1.4 SWR on the feedline may actually result in a 1.1 SWR at the other end of that residual reactance. The external wattmeter will indicate the SWR on the feedline - at the output of the KAT3. There is nothing the KAT3 can do to change that. In addition, many wattmeters are woefully inaccurate when reading SWR. Most All will be quite accurate for an SWR of 1.0, but at anything other than that, you will find a variation in the readings on amateur grade wattmeters. If you have a good dummy load (non-reactive 50 ohms), you can calibrate the K3 wattmeter (for power, not SWR). The procedure is in the Calibration section of the manual. 73, Don W3FPR On 11/17/2013 4:57 PM, pastor...@verizon.net wrote: John, the problem is that I don't have one of these. But thanks for the suggestion. One thing I have not tried is hooking up my antenna and external wattmeter coupler with Antenna 2 instead of Antenna 1. I am anxious to find out if I get the same readings with #2 as I did with #1. I guess I am rather perplexed at the thought that there is such a variance between the K3 wattmeter vs an external wattmeter. Especially, when I connected the coupler to the antenna #1 with a plug and then attached the antenna coax to the coupler. It's a shame that the K3 does not have a way of synching up the internal wattmeter with an external wattmeter. Hopefully somebody from elecraft will read this email and make a comment on it. Thanks to all with their responses. Mark Griffin, KB3Z __ 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] Internal K3 SWR vs Extermal SWR Meter
John, the problem is that I don't have one of these. But thanks for the suggestion. One thing I have not tried is hooking up my antenna and external wattmeter coupler with Antenna 2 instead of Antenna 1. I am anxious to find out if I get the same readings with #2 as I did with #1. I guess I am rather perplexed at the thought that there is such a variance between the K3 wattmeter vs an external wattmeter. Especially, when I connected the coupler to the antenna #1 with a plug and then attached the antenna coax to the coupler. It's a shame that the K3 does not have a way of synching up the internal wattmeter with an external wattmeter. Hopefully somebody from elecraft will read this email and make a comment on it. Thanks to all with their responses. Mark Griffin, KB3Z __ 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] Internal K3 SWR vs Extermal SWR Meter
A better way is to connect a load with a known SWR. Using a "BNC-BP BNC Male to Stackable Binding Posts" with three 100 Ohm 1W resistors in parallel, 33.3 Ohms, SWR should ~= 1.5. Directly connected to the K3, ATU in bypass, 5W output, measured SWR = 1.1. 18" piece of coax with W1 Power meter, same 33.3 ohm load, K3 SWR=1.1, W1 SWR=1.4 (Using W1 utility) My K3 is indicating a Low SWR at 5W output. John KN5L __ 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] Internal K3 SWR vs Extermal SWR Meter
Mark, You will get lots of responses to this. 99.9% of the folks on the Elecraft are more experienced and smarter than me. I have a similar situation with a WM-2 wattmeter and my KX3. Here's how I stopped worrying about it: 1. I realized that I have to bypass the ATU in the KX3 to get a "good" reading on the WM-2. 2. Even after doing #1, I still have a 2W discrepancy between the KX3 and the WM-2 (i.e. 5 W on the KX3 reads as 7 W on the WM-2). It varies at different bands and output power. 3. In my experience, wattmeters vary greatly and there is a deviation percentage that I think must be taken into account. I don't know what that amount is either. :) 4. When I use one, I am looking at an external wattmeter with a needle to get an instantaneous reading on reflected power. The needle is large and visible and I keep the meter in REV when I use it. This leads to an experience I had several years ago in a class on SCADA radios. The discussion of the Bird 43 wattmeter came up: I was once told that a Bird 43 wattmeter has about a 10 - 20% error rate (I forget the exact number). I told the guy I didn't care as long as it was the same inaccuracy when looking in both directions. I was looking for a *ratio*, not necessarily an output power. He looked at me like I was purple and had three eyes. I try to simplify things. The purists and the engineers out there will in all likelihood disagree with what I've said. I am sure there are instances where what I say will not or cannot work. In my casual operation as an amateur for 20 years, this has worked for me. In my professional career as a telecomm tech doing PMs and trouble-shooting on 37, 450, and 900 MHz radios for almost as long, this has worked. As with anything else I may say, this is just my experience. Your mileage may vary greatly... 73, Joel - W4JBB On 11/17/13, 11:01 AM, pastor...@verizon.net wrote: Good Morning, this is Mark Griffin and my call is KB3Z. I am having some real issues when it comes to getting a reliable SWR reading between my K3 and an external Wavenode Meter. I hooked up my hexbeam directly to the input Antenna 1 Connector of my K3 and got the following SWR readings in the SSB portion of the band. 20 Meters:1.1 17 Meters: 1.1 15 Meters: 1.8 12 Meters 2.7 10 Meters:1.4 Yes, I know that 12 meters is high for some reason! But I than hooked up my antenna to the Wavenode coupler and then to the my Antenna 1 connector and notice the differences between the K3 and the Wavenode. K3 Wavenode 20 Meters 1.11.6 17 Meters 1.11.4 15 Meters 1.82.3 12 Meters 2.71.9 10 Meters 1.41.7 Is anyone else out there experiencing the same issues between their K3 SWR and an external meter? Perhaps the wavenode coupler isn't good but I am so confused that I don't know what to do. Any assistance would be much appreciated. Mark Griffin, KB3Z __ 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] Internal K3 SWR vs Extermal SWR Meter
Good Morning, this is Mark Griffin and my call is KB3Z. I am having some real issues when it comes to getting a reliable SWR reading between my K3 and an external Wavenode Meter. I hooked up my hexbeam directly to the input Antenna 1 Connector of my K3 and got the following SWR readings in the SSB portion of the band. 20 Meters:1.1 17 Meters: 1.1 15 Meters: 1.8 12 Meters 2.7 10 Meters:1.4 Yes, I know that 12 meters is high for some reason! But I than hooked up my antenna to the Wavenode coupler and then to the my Antenna 1 connector and notice the differences between the K3 and the Wavenode. K3 Wavenode 20 Meters 1.11.6 17 Meters 1.11.4 15 Meters 1.82.3 12 Meters 2.71.9 10 Meters 1.41.7 Is anyone else out there experiencing the same issues between their K3 SWR and an external meter? Perhaps the wavenode coupler isn't good but I am so confused that I don't know what to do. Any assistance would be much appreciated. Mark Griffin, KB3Z __ 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
