Re: [Elecraft] W2 Questions
Jack, At $700 I will stick with my W7ZOI power meter with its 40 dB power tap and my Tandem Match! I have calibration data that Bob Friess provided on my Power meter from 1 MHz to 500 MHz (and ham band intervals in between). The Tandem Match tracks that data quite well in its basic metering, but is limited to 30 MHz with the couplers available. I really like the Tandem Match for general purposes, but the parallax from the analog meters must be taken into consideration too (op amp accuracy is a great thing indeed, nothing like analog computers using precision resistors - but then I am partly old school). That is certainly good enough to give me +/- 5% power measurement accuracy from 1 MHz to 500 MHz, and that is more than I require at the moment. The world of Power measurement is getting better, but it still is not down to really precise accuracy, no matter what the instrument. Thanks for the information. Perhaps one day when the ham budget allows and I have a purpose for it, I will make the investment. 73, Don W3FPR Jack Smith wrote: Don: All I've done is read the spec sheet, but Minicircuits has a relatively new sensitive termination wattmeter with USB interface for a quite reasonable price, at least by Agilent standards. http://www.minicircuits.com/pdfs/PWR-6G+.pdf -- it's a virtual instrument as it consists of the sensor and a USB port to plug into your computer. At $700, it isn't much more than you might pay for a single used Agilent sensor in decent shape and calibration. Depending on frequency and power range, the typical error runs from +/- 0.1 db to +/- 0.35 dB. power range from -30 to +20 dBm, frequency range 1 MHz - 6 GHz. If I didn't already have a 437B and 8481A and 8482A sensors, I would give the Minicircuits product serious consideration. Jack K8ZOA Don Wilhelm wrote: Phil, The W2 wattmeter is similar in its detector accuracy to the Tandem Match (by John Grebenkemper KI6WX) in that its accuracy depends on matching the detector diodes with the compensation diodes. The Gold Standard of power measuring devices is the HP436A wattmeter, and it has a stated accuracy of +/-0.05 dB. That amounts to a +/-1.16% accuracy - you are not going to get much better than that lab instrument in an amateur grade instrument. The Tandem Match that KI6WX built tracks the HP436A within +/- 0.5 dB over a range of 10 mW to 100W (your 11.2% error), and also tracks the HP436A within +/-0.1 dB over a 1W to 100W range for a 2.33 % difference. Power measurement is tough on accuracy as expressed in percentage. Most ham grade wattmeters specify 20% of full scale. The Tandem Match and the W2 wattmeter are percentages of actual readings. Since power is normally best expressed in dB (because the apparent signal strength is related in dB), a specification of 0.5 dB is not bad at all. BTW - I believe that is the accuracy of the power reported using the PC link. The resolution of the LED scale is not adequate to indicate the degree of precision available. The directional coupler will have frequency dependencies as well as accuracy implications. 73, Don W3FPR Phil Hystad wrote: A few questions about the W2 meter: 1. The posted accuracy is +- 0.5 dB which I calculate as about +- 12 %. Is this full scale accuracy and if so is half scale possibly more accurate or is this the most accurate the meter is likely to be. I am not even sure if it makes a difference for full scale or half scale for a digital meter so that part of my question may be moot. 2. What does it take to achieve an accuracy better then 5 % (for example), and is it possible to achieve an accuracy of 1 % or better? I am curious as to where the money needs to be spent in achieving such accuracy. Is it in the directional coupler? 3. I am thinking that the company that can build the best receiver on the market (the K3) can also build the best meter. So, would Elecraft principles consider a future super-accurate, best on the planet, amateur radio RF/SWR power meter? Oh, I think a current meter would be cool too. And, I know that having meter accuracy is of little importance in ham radio but there is some kind of deep seated quirk in me that wants accuracy just for the heck of it. Certainly 5 % is achievable, right? 73, phil, K7PEH __ 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 No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.709 / Virus Database: 270.14.100/2554 - Release Date: 12/09/09 02:32:00
[Elecraft] W2 Questions
A few questions about the W2 meter: 1. The posted accuracy is +- 0.5 dB which I calculate as about +- 12 %. Is this full scale accuracy and if so is half scale possibly more accurate or is this the most accurate the meter is likely to be. I am not even sure if it makes a difference for full scale or half scale for a digital meter so that part of my question may be moot. 2. What does it take to achieve an accuracy better then 5 % (for example), and is it possible to achieve an accuracy of 1 % or better? I am curious as to where the money needs to be spent in achieving such accuracy. Is it in the directional coupler? 3. I am thinking that the company that can build the best receiver on the market (the K3) can also build the best meter. So, would Elecraft principles consider a future super-accurate, best on the planet, amateur radio RF/SWR power meter? Oh, I think a current meter would be cool too. And, I know that having meter accuracy is of little importance in ham radio but there is some kind of deep seated quirk in me that wants accuracy just for the heck of it. Certainly 5 % is achievable, right? 73, phil, K7PEH __ 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] W2 Questions
Phil, With each LED representing 100-watts on the 2KW scale, it may be of some help to go from 10% to 5% in accuracy, but in the case of the W2, the display resolution is limited to 50-watts in between mid power ranges (e.g., 250-watts) but a display of 200-watts with two LEDs showing may actually mean 151 watts or 249 watts. 50-watts is mid-way between any two LEDs at the 2KW range and I'm making an assumption that levels less than any 50-watt range (e.g., 240-watts) will result in the preceding element being lit which shows 200-watts. If it's more than the mid point (e.g., 260-watts) then the next LED should be lit. So, at the low-end of the W2's range at say the 200-watt level, the meter can at best resolve to only 50/200 = 25% and seemingly 100/200 = 50% at worst (using the 149W to 249W example). I don't want to confuse resolution with accuracy but the two parameters go hand-in-hand. That said, I see no real benefit of going from 10% to 5% in accuracy when resolution deficiencies can easily mask the error in accuracy. I may be completely wrong with the manner in which the W2 resolves, so someone set me straight if my assumptions aren't correct. You asked the question about what it takes to achieve better accuracy. You may want to read N8LP's excellent article in QEX from a few years ago, along with articles from Warren Bruene, Roy Lewallen, John Grebenkemper, and others who have published on the accuracy subject. Paul, W9AC - Original Message - From: Phil Hystad k7...@comcast.net To: Elecraft elecraft@mailman.qth.net Sent: Wednesday, December 09, 2009 7:51 PM Subject: [Elecraft] W2 Questions A few questions about the W2 meter: 1. The posted accuracy is +- 0.5 dB which I calculate as about +- 12 %. Is this full scale accuracy and if so is half scale possibly more accurate or is this the most accurate the meter is likely to be. I am not even sure if it makes a difference for full scale or half scale for a digital meter so that part of my question may be moot. 2. What does it take to achieve an accuracy better then 5 % (for example), and is it possible to achieve an accuracy of 1 % or better? I am curious as to where the money needs to be spent in achieving such accuracy. Is it in the directional coupler? 3. I am thinking that the company that can build the best receiver on the market (the K3) can also build the best meter. So, would Elecraft principles consider a future super-accurate, best on the planet, amateur radio RF/SWR power meter? Oh, I think a current meter would be cool too. And, I know that having meter accuracy is of little importance in ham radio but there is some kind of deep seated quirk in me that wants accuracy just for the heck of it. Certainly 5 % is achievable, right? 73, phil, K7PEH __ 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] W2 Questions
Paul, Thanks for your comments. And, in followup, if Elecraft were to make a meter with reasonably high accuracy I presume that another display method, other then LEDs, would be required. I think a high-resolution LCD with nice color graphic renditions of power information. OK, sort of kidding here, I presume that a computer interface could handle that kind of information display. peh On Dec 9, 2009, at 5:23 PM, Paul Christensen wrote: Phil, With each LED representing 100-watts on the 2KW scale, it may be of some help to go from 10% to 5% in accuracy, but in the case of the W2, the display resolution is limited to 50-watts in between mid power ranges (e.g., 250-watts) but a display of 200-watts with two LEDs showing may actually mean 151 watts or 249 watts. 50-watts is mid-way between any two LEDs at the 2KW range and I'm making an assumption that levels less than any 50-watt range (e.g., 240-watts) will result in the preceding element being lit which shows 200-watts. If it's more than the mid point (e.g., 260-watts) then the next LED should be lit. So, at the low-end of the W2's range at say the 200-watt level, the meter can at best resolve to only 50/200 = 25% and seemingly 100/200 = 50% at worst (using the 149W to 249W example). I don't want to confuse resolution with accuracy but the two parameters go hand-in-hand. That said, I see no real benefit of going from 10% to 5% in accuracy when resolution deficiencies can easily mask the error in accuracy. I may be completely wrong with the manner in which the W2 resolves, so someone set me straight if my assumptions aren't correct. You asked the question about what it takes to achieve better accuracy. You may want to read N8LP's excellent article in QEX from a few years ago, along with articles from Warren Bruene, Roy Lewallen, John Grebenkemper, and others who have published on the accuracy subject. Paul, W9AC - Original Message - From: Phil Hystad k7...@comcast.net To: Elecraft elecraft@mailman.qth.net Sent: Wednesday, December 09, 2009 7:51 PM Subject: [Elecraft] W2 Questions A few questions about the W2 meter: 1. The posted accuracy is +- 0.5 dB which I calculate as about +- 12 %. Is this full scale accuracy and if so is half scale possibly more accurate or is this the most accurate the meter is likely to be. I am not even sure if it makes a difference for full scale or half scale for a digital meter so that part of my question may be moot. 2. What does it take to achieve an accuracy better then 5 % (for example), and is it possible to achieve an accuracy of 1 % or better? I am curious as to where the money needs to be spent in achieving such accuracy. Is it in the directional coupler? 3. I am thinking that the company that can build the best receiver on the market (the K3) can also build the best meter. So, would Elecraft principles consider a future super-accurate, best on the planet, amateur radio RF/SWR power meter? Oh, I think a current meter would be cool too. And, I know that having meter accuracy is of little importance in ham radio but there is some kind of deep seated quirk in me that wants accuracy just for the heck of it. Certainly 5 % is achievable, right? 73, phil, K7PEH __ 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] W2 Questions
It's kinda' hard to beat numerical digits when you want the best possible resolution displayed. By the way Phil, I should re-phrase my earlier statement when I referred to a resolution deficiency. I really meant to imply a resolution limitation. There's nothing wrong with that form of wattmeter display, even with the set limitation on resolution. I prefer a bargraph display as a quick indicator of what's going on rather than interpolating quickly flashing numbers on a display. Here's a link to N8LP's article in QEX. Accuracy is highly dependent on directional coupler design and construction technique as well as detector design. http://www.telepostinc.com/Files/phipps-1.pdf Paul, W9AC - Original Message - From: Phil Hystad k7...@comcast.net To: Paul Christensen w...@arrl.net Cc: Elecraft elecraft@mailman.qth.net Sent: Wednesday, December 09, 2009 8:37 PM Subject: Re: [Elecraft] W2 Questions Paul, Thanks for your comments. And, in followup, if Elecraft were to make a meter with reasonably high accuracy I presume that another display method, other then LEDs, would be required. I think a high-resolution LCD with nice color graphic renditions of power information. OK, sort of kidding here, I presume that a computer interface could handle that kind of information display. peh On Dec 9, 2009, at 5:23 PM, Paul Christensen wrote: Phil, With each LED representing 100-watts on the 2KW scale, it may be of some help to go from 10% to 5% in accuracy, but in the case of the W2, the display resolution is limited to 50-watts in between mid power ranges (e.g., 250-watts) but a display of 200-watts with two LEDs showing may actually mean 151 watts or 249 watts. 50-watts is mid-way between any two LEDs at the 2KW range and I'm making an assumption that levels less than any 50-watt range (e.g., 240-watts) will result in the preceding element being lit which shows 200-watts. If it's more than the mid point (e.g., 260-watts) then the next LED should be lit. So, at the low-end of the W2's range at say the 200-watt level, the meter can at best resolve to only 50/200 = 25% and seemingly 100/200 = 50% at worst (using the 149W to 249W example). I don't want to confuse resolution with accuracy but the two parameters go hand-in-hand. That said, I see no real benefit of going from 10% to 5% in accuracy when resolution deficiencies can easily mask the error in accuracy. I may be completely wrong with the manner in which the W2 resolves, so someone set me straight if my assumptions aren't correct. You asked the question about what it takes to achieve better accuracy. You may want to read N8LP's excellent article in QEX from a few years ago, along with articles from Warren Bruene, Roy Lewallen, John Grebenkemper, and others who have published on the accuracy subject. Paul, W9AC - Original Message - From: Phil Hystad k7...@comcast.net To: Elecraft elecraft@mailman.qth.net Sent: Wednesday, December 09, 2009 7:51 PM Subject: [Elecraft] W2 Questions A few questions about the W2 meter: 1. The posted accuracy is +- 0.5 dB which I calculate as about +- 12 %. Is this full scale accuracy and if so is half scale possibly more accurate or is this the most accurate the meter is likely to be. I am not even sure if it makes a difference for full scale or half scale for a digital meter so that part of my question may be moot. 2. What does it take to achieve an accuracy better then 5 % (for example), and is it possible to achieve an accuracy of 1 % or better? I am curious as to where the money needs to be spent in achieving such accuracy. Is it in the directional coupler? 3. I am thinking that the company that can build the best receiver on the market (the K3) can also build the best meter. So, would Elecraft principles consider a future super-accurate, best on the planet, amateur radio RF/SWR power meter? Oh, I think a current meter would be cool too. And, I know that having meter accuracy is of little importance in ham radio but there is some kind of deep seated quirk in me that wants accuracy just for the heck of it. Certainly 5 % is achievable, right? 73, phil, K7PEH __ 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
Re: [Elecraft] W2 Questions
Phil, The W2 wattmeter is similar in its detector accuracy to the Tandem Match (by John Grebenkemper KI6WX) in that its accuracy depends on matching the detector diodes with the compensation diodes. The Gold Standard of power measuring devices is the HP436A wattmeter, and it has a stated accuracy of +/-0.05 dB. That amounts to a +/-1.16% accuracy - you are not going to get much better than that lab instrument in an amateur grade instrument. The Tandem Match that KI6WX built tracks the HP436A within +/- 0.5 dB over a range of 10 mW to 100W (your 11.2% error), and also tracks the HP436A within +/-0.1 dB over a 1W to 100W range for a 2.33 % difference. Power measurement is tough on accuracy as expressed in percentage. Most ham grade wattmeters specify 20% of full scale. The Tandem Match and the W2 wattmeter are percentages of actual readings. Since power is normally best expressed in dB (because the apparent signal strength is related in dB), a specification of 0.5 dB is not bad at all. BTW - I believe that is the accuracy of the power reported using the PC link. The resolution of the LED scale is not adequate to indicate the degree of precision available. The directional coupler will have frequency dependencies as well as accuracy implications. 73, Don W3FPR Phil Hystad wrote: A few questions about the W2 meter: 1. The posted accuracy is +- 0.5 dB which I calculate as about +- 12 %. Is this full scale accuracy and if so is half scale possibly more accurate or is this the most accurate the meter is likely to be. I am not even sure if it makes a difference for full scale or half scale for a digital meter so that part of my question may be moot. 2. What does it take to achieve an accuracy better then 5 % (for example), and is it possible to achieve an accuracy of 1 % or better? I am curious as to where the money needs to be spent in achieving such accuracy. Is it in the directional coupler? 3. I am thinking that the company that can build the best receiver on the market (the K3) can also build the best meter. So, would Elecraft principles consider a future super-accurate, best on the planet, amateur radio RF/SWR power meter? Oh, I think a current meter would be cool too. And, I know that having meter accuracy is of little importance in ham radio but there is some kind of deep seated quirk in me that wants accuracy just for the heck of it. Certainly 5 % is achievable, right? 73, phil, K7PEH __ 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] W2 Questions
Within 0.5 dB worst case of the actual power being measured. Not of full scale. We actually do much better than that. 73, Eric Phil Hystad wrote: A few questions about the W2 meter: 1. The posted accuracy is +- 0.5 dB which I calculate as about +- 12 %. Is this full scale accuracy and if so is half scale possibly more accurate or is this the most accurate the meter is likely to be. I am not even sure if it makes a difference for full scale or half scale for a digital meter so that part of my question may be moot. __ 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] W2 Questions [pending firmware changes and software applications]
We'll be making a number of improvements to W2 firmware in future releases (starting in January). Firmware updates are very easy to do on the W2, and the required serial cable is supplied. For example, the last LED segment illuminated will be able to show a range of intensities (from off to fully on), allowing you to resolve power steps with finer granularity than the panel labeling. This will be especially useful when peaking amplifiers. We also have PC and Mac software applications in the works that will provide very high-resolution bargraphs and additional features. 73, Wayne N6KR __ 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] W2 Questions
And take a look at HP's note AN64 (cp.literature.agilent.com/litweb/pdf/5965-6630E.pdf), particularly chapter VII. After that, the question about whether more resolution is necessary or meaningful might be moot. --- On Wed, 12/9/09, Paul Christensen w...@arrl.net wrote: You asked the question about what it takes to achieve better accuracy. You may want to read N8LP's excellent article in QEX from a few years ago, along with articles from Warren Bruene, Roy Lewallen, John Grebenkemper, and others who have published on the accuracy subject. Paul, W9AC - Original Message - From: Phil Hystad k7...@comcast.net To: Elecraft elecraft@mailman.qth.net Sent: Wednesday, December 09, 2009 7:51 PM Subject: [Elecraft] W2 Questions A few questions about the W2 meter: 1. The posted accuracy is +- 0.5 dB which I calculate as about +- 12 %. Is this full scale accuracy and if so is half scale possibly more accurate or is this the most accurate the meter is likely to be. I am not even sure if it makes a difference for full scale or half scale for a digital meter so that part of my question may be moot. 2. What does it take to achieve an accuracy better then 5 % (for example), and is it possible to achieve an accuracy of 1 % or better? I am curious as to where the money needs to be spent in achieving such accuracy. Is it in the directional coupler? 3. I am thinking that the company that can build the best receiver on the market (the K3) can also build the best meter. So, would Elecraft principles consider a future super-accurate, best on the planet, amateur radio RF/SWR power meter? Oh, I think a current meter would be cool too. And, I know that having meter accuracy is of little importance in ham radio but there is some kind of deep seated quirk in me that wants accuracy just for the heck of it. Certainly 5 % is achievable, right? 73, phil, K7PEH __ 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] W2 Questions
Don: All I've done is read the spec sheet, but Minicircuits has a relatively new sensitive termination wattmeter with USB interface for a quite reasonable price, at least by Agilent standards. http://www.minicircuits.com/pdfs/PWR-6G+.pdf -- it's a virtual instrument as it consists of the sensor and a USB port to plug into your computer. At $700, it isn't much more than you might pay for a single used Agilent sensor in decent shape and calibration. Depending on frequency and power range, the typical error runs from +/- 0.1 db to +/- 0.35 dB. power range from -30 to +20 dBm, frequency range 1 MHz - 6 GHz. If I didn't already have a 437B and 8481A and 8482A sensors, I would give the Minicircuits product serious consideration. Jack K8ZOA Don Wilhelm wrote: Phil, The W2 wattmeter is similar in its detector accuracy to the Tandem Match (by John Grebenkemper KI6WX) in that its accuracy depends on matching the detector diodes with the compensation diodes. The Gold Standard of power measuring devices is the HP436A wattmeter, and it has a stated accuracy of +/-0.05 dB. That amounts to a +/-1.16% accuracy - you are not going to get much better than that lab instrument in an amateur grade instrument. The Tandem Match that KI6WX built tracks the HP436A within +/- 0.5 dB over a range of 10 mW to 100W (your 11.2% error), and also tracks the HP436A within +/-0.1 dB over a 1W to 100W range for a 2.33 % difference. Power measurement is tough on accuracy as expressed in percentage. Most ham grade wattmeters specify 20% of full scale. The Tandem Match and the W2 wattmeter are percentages of actual readings. Since power is normally best expressed in dB (because the apparent signal strength is related in dB), a specification of 0.5 dB is not bad at all. BTW - I believe that is the accuracy of the power reported using the PC link. The resolution of the LED scale is not adequate to indicate the degree of precision available. The directional coupler will have frequency dependencies as well as accuracy implications. 73, Don W3FPR Phil Hystad wrote: A few questions about the W2 meter: 1. The posted accuracy is +- 0.5 dB which I calculate as about +- 12 %. Is this full scale accuracy and if so is half scale possibly more accurate or is this the most accurate the meter is likely to be. I am not even sure if it makes a difference for full scale or half scale for a digital meter so that part of my question may be moot. 2. What does it take to achieve an accuracy better then 5 % (for example), and is it possible to achieve an accuracy of 1 % or better? I am curious as to where the money needs to be spent in achieving such accuracy. Is it in the directional coupler? 3. I am thinking that the company that can build the best receiver on the market (the K3) can also build the best meter. So, would Elecraft principles consider a future super-accurate, best on the planet, amateur radio RF/SWR power meter? Oh, I think a current meter would be cool too. And, I know that having meter accuracy is of little importance in ham radio but there is some kind of deep seated quirk in me that wants accuracy just for the heck of it. Certainly 5 % is achievable, right? 73, phil, K7PEH __ 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] W2 Questions
Wes, Thanks for the link to what looks like a very interesting document. Just what I have been looking for. And, thanks to others for the suggested resources. phil On Dec 9, 2009, at 7:01 PM, Wes Stewart wrote: And take a look at HP's note AN64 (cp.literature.agilent.com/litweb/pdf/5965-6630E.pdf), particularly chapter VII. After that, the question about whether more resolution is necessary or meaningful might be moot. --- On Wed, 12/9/09, Paul Christensen w...@arrl.net wrote: You asked the question about what it takes to achieve better accuracy. You may want to read N8LP's excellent article in QEX from a few years ago, along with articles from Warren Bruene, Roy Lewallen, John Grebenkemper, and others who have published on the accuracy subject. Paul, W9AC - Original Message - From: Phil Hystad k7...@comcast.net To: Elecraft elecraft@mailman.qth.net Sent: Wednesday, December 09, 2009 7:51 PM Subject: [Elecraft] W2 Questions A few questions about the W2 meter: 1. The posted accuracy is +- 0.5 dB which I calculate as about +- 12 %. Is this full scale accuracy and if so is half scale possibly more accurate or is this the most accurate the meter is likely to be. I am not even sure if it makes a difference for full scale or half scale for a digital meter so that part of my question may be moot. 2. What does it take to achieve an accuracy better then 5 % (for example), and is it possible to achieve an accuracy of 1 % or better? I am curious as to where the money needs to be spent in achieving such accuracy. Is it in the directional coupler? 3. I am thinking that the company that can build the best receiver on the market (the K3) can also build the best meter. So, would Elecraft principles consider a future super-accurate, best on the planet, amateur radio RF/SWR power meter? Oh, I think a current meter would be cool too. And, I know that having meter accuracy is of little importance in ham radio but there is some kind of deep seated quirk in me that wants accuracy just for the heck of it. Certainly 5 % is achievable, right? 73, phil, K7PEH __ 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 __ 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] W2 Questions
Jack, At $700 I will stick with my W7ZOI power meter with its 40 dB power tap and my Tandem Match! I have calibration data that Bob Friess provided on my Power meter from 1 MHz to 500 MHz (and ham band intervals in between). The Tandem Match tracks that data quite well in its basic metering, but is limited to 30 MHz with the couplers available. I really like the Tandem Match for general purposes, but the parallax from the analog meters must be taken into consideration too (op amp accuracy is a great thing indeed, nothing like analog computers using precision resistors - but then I am partly old school). That is certainly good enough to give me ± 5% power measurement accuracy from 1 MHz to 500 MHz, and that is more than I require at the moment. The world of Power measurement is getting better, but it still is not down to really precise accuracy, no matter what the instrument. Thanks for the information. Perhaps one day when the ham budget allows and I have a purpose for it, I will make the investment. 73, Don W3FPR Jack Smith wrote: Don: All I've done is read the spec sheet, but Minicircuits has a relatively new sensitive termination wattmeter with USB interface for a quite reasonable price, at least by Agilent standards. http://www.minicircuits.com/pdfs/PWR-6G+.pdf -- it's a virtual instrument as it consists of the sensor and a USB port to plug into your computer. At $700, it isn't much more than you might pay for a single used Agilent sensor in decent shape and calibration. Depending on frequency and power range, the typical error runs from +/- 0.1 db to +/- 0.35 dB. power range from -30 to +20 dBm, frequency range 1 MHz - 6 GHz. If I didn't already have a 437B and 8481A and 8482A sensors, I would give the Minicircuits product serious consideration. Jack K8ZOA __ 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
