K1 AutoTuner KAT1
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I recently completed the K1 with the optional KAT1 tuner. I have already aligned and tested the K1 without the autotuner installed and it works perfectly. I am trying to align the KAT1 but I am having an issue with the power calibration. I adjusted C9 to the lowest voltage, about 60mv. After I switch to CLP I make sure the output power is 5w using an oscilloscope. I then try to adjust the reading on the lCD display to match the output power but can never go about 2.2w. The only way to match the power out is to adjust C9. I know I am forgetting a small step somewhere but I am tired of messing with it.
I have also cycled through all of the relay switches to ensure they work. Nate |
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Nate,
I have trouble believing the KAT1 is not differentiating between 2.2 watts and 5 watts. Are you certain you are reading the 'scope correctly? At 5 watts, the peak to peak RF voltage shown on the 'scope will be 44.72 volts. You must use a 10X probe across the dummy load for accurate results and calibrate the probe using the 'scope's calibrator for a nice square wave of the correct amplitude. Actually it is easier to use a 4 watt output - that is exactly 40 volts peak to peak deflection on the 'scope. To quickly (and precisely) calculate the power from the peak to peak voltage, square the peak to peak voltage reading and divide by 400 to obtain the power with a 50 ohm load. Now to answer your question. C9 *must* be set to the null point using a very accurate 50 ohm load. That load must have no reactance if you are to achieve accurate calibration results. Measure the dummy load with an antenna analyzer if you do not know its accuracy. After adjusting C9, and using the same accurate dummy load, adjust the K1 power output to indicate 40 volts peak to peak deflection on the 'scope and adjust the FWD pot to indicate 4 watts on the K1. You my have to make several interative steps until the 'scope indication and the display agree. Expect a +/- 1 digit variation in the K1 power display, so 3.9, 4.0 and 4.1 may all indicate a nominal 4 watts output. dogbulter wrote: > I recently completed the K1 with the optional KAT1 tuner. I have already aligned and tested the K1 without the autotuner installed and it works perfectly. I am trying to align the KAT1 but I am having an issue with the power calibration. I adjusted C9 to the lowest voltage, about 60mv. After I switch to CLP I make sure the output power is 5w using an oscilloscope. I then try to adjust the reading on the lCD display to match the output power but can never go about 2.2w. The only way to match the power out is to adjust C9. I know I am forgetting a small step somewhere but I am tired of messing with it. > > I have also cycled through all of the relay switches to ensure they work. > > Nate > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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I am using the VRMS formula to calculate the power output so my measurements are very accurate. I am using a digital O-scope that even displays the pp voltage which is always above 40vpp depending on the band. I am using a 50ohm dummy load which has been verified with a meter and it exactly 50ohms.
I am calculating the power output by using VRMS= 0.707(Vpp/2) VRMS^2/50ohms= Watts out. So like I said when I adjust R1 I can not get the LCD display to read above 2.2w after adjusting C9. Date: Wed, 25 Mar 2009 05:59:17 -0700 From: [hidden email] To: [hidden email] Subject: Re: K1 AutoTuner KAT1 Nate, I have trouble believing the KAT1 is not differentiating between 2.2 watts and 5 watts. Are you certain you are reading the 'scope correctly? At 5 watts, the peak to peak RF voltage shown on the 'scope will be 44.72 volts. You must use a 10X probe across the dummy load for accurate results and calibrate the probe using the 'scope's calibrator for a nice square wave of the correct amplitude. Actually it is easier to use a 4 watt output - that is exactly 40 volts peak to peak deflection on the 'scope. To quickly (and precisely) calculate the power from the peak to peak voltage, square the peak to peak voltage reading and divide by 400 to obtain the power with a 50 ohm load. Now to answer your question. C9 *must* be set to the null point using a very accurate 50 ohm load. That load must have no reactance if you are to achieve accurate calibration results. Measure the dummy load with an antenna analyzer if you do not know its accuracy. After adjusting C9, and using the same accurate dummy load, adjust the K1 power output to indicate 40 volts peak to peak deflection on the 'scope and adjust the FWD pot to indicate 4 watts on the K1. You my have to make several interative steps until the 'scope indication and the display agree. Expect a +/- 1 digit variation in the K1 power display, so 3.9, 4.0 and 4.1 may all indicate a nominal 4 watts output. dogbulter wrote: > I recently completed the K1 with the optional KAT1 tuner. I have already aligned and tested the K1 without the autotuner installed and it works perfectly. I am trying to align the KAT1 but I am having an issue with the power calibration. I adjusted C9 to the lowest voltage, about 60mv. After I switch to CLP I make sure the output power is 5w using an oscilloscope. I then try to adjust the reading on the lCD display to match the output power but can never go about 2.2w. The only way to match the power out is to adjust C9. I know I am forgetting a small step somewhere but I am tired of messing with it. > > I have also cycled through all of the relay switches to ensure they work. > > Nate > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@... This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html This email is a reply to your post @ http://n2.nabble.com/K1-AutoTuner-KAT1-tp2532020p2532234.html You can reply by email or by visting the link above. Internet Explorer 8 – Now Available. Faster, safer, easier. Download FREE now! |
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Nate,
You are doing the math correctly, but it is not only easier to use the Vp-p^2/400 formula, but is slightly more accurate because it is derived using sqrt(2)/2 for the RMS conversion rather than using the approximation of .707. That still does not explain the large discrepancy, either you have a fault with the wattmeter section of the KAT1 or you may have forgotten to change the jumper at the back of the RF board from K1 to KAT1. Do check your dummy load too. If the dummy load resistance is high, that would explain why you are seeing a greater RF voltage on your 'scope - check it at the frequency of operation with an antenna analyzer, you are looking for 50 ohms pure resistance and no reactance. A little bit of variation from that can make a big difference in the power measurement technique you are using - it does depend on the accuracy of the dummy load. 73, Don W3FPR dogbulter wrote: > I am using the VRMS formula to calculate the power output so my measurements are very accurate. I am using a digital O-scope that even displays the pp voltage which is always above 40vpp depending on the band. I am using a 50ohm dummy load which has been verified with a meter and it exactly 50ohms. > > > > I am calculating the power output by using VRMS= 0.707(Vpp/2) VRMS^2/50ohms= Watts out. > > > > So like I said when I adjust R1 I can not get the LCD display to read above 2.2w after adjusting C9. > > > > > > > Date: Wed, 25 Mar 2009 05:59:17 -0700 > From: [hidden email] > To: [hidden email] > Subject: Re: K1 AutoTuner KAT1 > > Nate, > > I have trouble believing the KAT1 is not differentiating between 2.2 > watts and 5 watts. > Are you certain you are reading the 'scope correctly? At 5 watts, the > peak to peak RF voltage shown on the 'scope will be 44.72 volts. You > must use a 10X probe across the dummy load for accurate results and > calibrate the probe using the 'scope's calibrator for a nice square wave > of the correct amplitude. > > Actually it is easier to use a 4 watt output - that is exactly 40 volts > peak to peak deflection on the 'scope. > To quickly (and precisely) calculate the power from the peak to peak > voltage, square the peak to peak voltage reading and divide by 400 to > obtain the power with a 50 ohm load. > > Now to answer your question. C9 *must* be set to the null point using a > very accurate 50 ohm load. That load must have no reactance if you are > to achieve accurate calibration results. Measure the dummy load with an > antenna analyzer if you do not know its accuracy. > > After adjusting C9, and using the same accurate dummy load, adjust the > K1 power output to indicate 40 volts peak to peak deflection on the > 'scope and adjust the FWD pot to indicate 4 watts on the K1. You my > have to make several interative steps until the 'scope indication and > the display agree. Expect a +/- 1 digit variation in the K1 power > display, so 3.9, 4.0 and 4.1 may all indicate a nominal 4 watts output. > > dogbulter wrote: > >> I recently completed the K1 with the optional KAT1 tuner. I have already aligned and tested the K1 without the autotuner installed and it works perfectly. I am trying to align the KAT1 but I am having an issue with the power calibration. I adjusted C9 to the lowest voltage, about 60mv. After I switch to CLP I make sure the output power is 5w using an oscilloscope. I then try to adjust the reading on the lCD display to match the output power but can never go about 2.2w. The only way to match the power out is to adjust C9. I know I am forgetting a small step somewhere but I am tired of messing with it. >> >> I have also cycled through all of the relay switches to ensure they work. >> >> Nate >> >> >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@... > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > > > > > > This email is a reply to your post @ http://n2.nabble.com/K1-AutoTuner-KAT1-tp2532020p2532234.html > You can reply by email or by visting the link above. > > > _________________________________________________________________ > Internet Explorer 8 – Now Available. Faster, safer, easier. > http://clk.atdmt.com/MRT/go/141323790/direct/01/ > > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.0.238 / Virus Database: 270.11.28/2022 - Release Date: 03/25/09 07:16:00 > > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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