Re: [Elecraft] KPA1500 Linearity
To make these kinds of measurements with amateur equipment and accuracy, I suggest acquiring some directional couplers and/or high power attenuators. A spare K3 or a decent SDR receiver then makes an excellent "power meter" with significant dynamic range. Gain measurements are really ratio measurements and seldom, if ever, require NIST traceability. The ancillary hardware can be characterized by substitution. One further point: Although it's possible that two 10% accuracy power meters will have 20% uncertainty, it's highly improbable. In industry, all uncertainties: mismatch errors due to reflection coefficients of sources and power sensors, linearity errors, noise, temperature effects, etc are combined into one uncertainty by RSSing the individual errors. You never add all the worse cases to get the answer. Wes N7WS On 6/19/2018 3:42 PM, Don Wilhelm wrote: John, You are exactly right for bring that factor to attention. Typically wattmeters use diodes in their detectors, and the response will vary by frequency and by the power level. I would trust only something that has been calibrated to NIST traceable standards. The Telepost LP-100 is one example (and those are used on many Elecraft test benches). While 10% is an OK deviation for amateur purposes, two wattmeters each with 10% accuracy can lead to a 20% error in the final measurements. It is too easy to jump to conclusions by not considering the potential errors in measurement accuracy. If you want 5% accuracy in your conclusions, your measurement tools should be accurate to 0.5% - a far stretch for wattmeters as we know them. 73, Don W3FPR On 6/19/2018 6:25 PM, John Oppenheimer wrote: Hi Scott, I wonder how the linearity of the two power meters was evaluated? Some years ago I checked the K3 and KX3 power meter against two other meters. They were just within 10% http://www.kn5l.net/Elecraft/Power.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 Message delivered to wes_n...@triconet.org __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
The saturation can be due: - transistor limit -not the case here - power supply drop - not if well designed switching PS or a commercial unit - winding ratio in final transistor module You can test the last one by measuring max power at saturation. Should be at least 2 KW. I have Expert 2k-fa that has 6 transistor modules rated at 300W. Saturated power around 2.0 KW as measured by LP100; 2k's meter shows 2.4 K. Ignacy, NO9E -- Sent from: http://elecraft.365791.n2.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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
Yes, the linearity of the two power meters is suspect. However, the compression of interest is near the high end for that of both the KPA1500 and the K3, so I wouldn't expect their nonlinearity there to make much difference. Note that absolute accuracy isn't critical. 73, Scott K9MA On 6/19/2018 17:42, Don Wilhelm wrote: John, You are exactly right for bring that factor to attention. Typically wattmeters use diodes in their detectors, and the response will vary by frequency and by the power level. I would trust only something that has been calibrated to NIST traceable standards. The Telepost LP-100 is one example (and those are used on many Elecraft test benches). While 10% is an OK deviation for amateur purposes, two wattmeters each with 10% accuracy can lead to a 20% error in the final measurements. It is too easy to jump to conclusions by not considering the potential errors in measurement accuracy. If you want 5% accuracy in your conclusions, your measurement tools should be accurate to 0.5% - a far stretch for wattmeters as we know them. 73, Don W3FPR On 6/19/2018 6:25 PM, John Oppenheimer wrote: Hi Scott, I wonder how the linearity of the two power meters was evaluated? Some years ago I checked the K3 and KX3 power meter against two other meters. They were just within 10% http://www.kn5l.net/Elecraft/Power.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 Message delivered to k...@sdellington.us -- Scott K9MA k...@sdellington.us __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
Yes and most power meters are voltage sensing instruments which are calibrated to a specific value or load. Thus is the load being used may not be the identical value to which it was calibrated, hence another error enters the equation. To wit, I have 3 "allegedly" 50 ohm dummy loads. Only one is actually 50 ohms but others are as low as 45 ohms and as high as 58 ohms, while one actually measures 50.5 ohms. If one is trying to measure power then both voltage and current should be measured with a known load and then do the math. If you are using an antenna, it most likely is somewhat reactive. This throws another curve into the ballpark in terms of power measurement. 73 Bob, K4TAX On 6/19/2018 7:15 PM, Fred Jensen wrote: Most, if not all analog measurement devices are spec'd at % of full scale which can lead to high absolute variances if the levels being measured are significantly below full scale. A Bird with a 100W slug accurate to 10% of full scale [+/- 5W] would be within spec if it indicated a real 10 W signal at 5 W. Many folks would say, "My K2/10 will only produce half the power it should." Most digital measurements involve processing circuitry/computation, again which can introduce errors in the lower end of a range, and be dependent on frequency as well. Mathematics can be hard. Arithmetic can be tricky. [:-) 73, Fred ["Skip"] K6DGW Sparks NV DM09dn Washoe County __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
Most, if not all analog measurement devices are spec'd at % of full scale which can lead to high absolute variances if the levels being measured are significantly below full scale. A Bird with a 100W slug accurate to 10% of full scale [+/- 5W] would be within spec if it indicated a real 10 W signal at 5 W. Many folks would say, "My K2/10 will only produce half the power it should." Most digital measurements involve processing circuitry/computation, again which can introduce errors in the lower end of a range, and be dependent on frequency as well. Mathematics can be hard. Arithmetic can be tricky. [:-) 73, Fred ["Skip"] K6DGW Sparks NV DM09dn Washoe County On 6/19/2018 3:25 PM, John Oppenheimer wrote: Hi Scott, I wonder how the linearity of the two power meters was evaluated? Some years ago I checked the K3 and KX3 power meter against two other meters. They were just within 10% http://www.kn5l.net/Elecraft/Power.html John KN5L On 06/19/2018 04:56 PM, K9MA wrote: I just repeated the linearity measurements, on both 40 and 15 meters. I used the KPA1500 meter to measure output, and the K3 power setting for input. __ 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 Message delivered to k6...@foothill.net __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
John, You are exactly right for bring that factor to attention. Typically wattmeters use diodes in their detectors, and the response will vary by frequency and by the power level. I would trust only something that has been calibrated to NIST traceable standards. The Telepost LP-100 is one example (and those are used on many Elecraft test benches). While 10% is an OK deviation for amateur purposes, two wattmeters each with 10% accuracy can lead to a 20% error in the final measurements. It is too easy to jump to conclusions by not considering the potential errors in measurement accuracy. If you want 5% accuracy in your conclusions, your measurement tools should be accurate to 0.5% - a far stretch for wattmeters as we know them. 73, Don W3FPR On 6/19/2018 6:25 PM, John Oppenheimer wrote: Hi Scott, I wonder how the linearity of the two power meters was evaluated? Some years ago I checked the K3 and KX3 power meter against two other meters. They were just within 10% http://www.kn5l.net/Elecraft/Power.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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
Hi Scott, I wonder how the linearity of the two power meters was evaluated? Some years ago I checked the K3 and KX3 power meter against two other meters. They were just within 10% http://www.kn5l.net/Elecraft/Power.html John KN5L On 06/19/2018 04:56 PM, K9MA wrote: > I just repeated the linearity measurements, on both 40 and 15 meters. I > used the KPA1500 meter to measure output, and the K3 power setting for > input. __ 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 Message delivered to arch...@mail-archive.com
[Elecraft] KPA1500 Linearity
I just repeated the linearity measurements, on both 40 and 15 meters. I used the KPA1500 meter to measure output, and the K3 power setting for input. Results on the two bands were similar, though 15 required much more drive. On 40, the maximum gain occurred at about 800 W out, 17.2 dB. At 1 kW, it was 16.9 dB, and at 1.5 kW it was 15.7 dB. However, at 1.45 kW the gain was 16.2 dB, so there was a lot of compression in that last 55 W. The gain compression at 1.5 kW vs 1 kW is 1.2 dB, but only 0.7 dB at 1.45 kW. Overall, I'm told this compression is typical of the KPA1500, and probably doesn't indicate excessive IMD, at least compared to other solid-state amplifiers. It's probably a good idea to be very careful not to overdrive it on SSB, though. The gain drops off at low power, to 16.0 dB at 200 W. This is consistent with the BLF188 data sheet. However, the data sheet shows the gain almost perfectly flat to over 1 kW per device. They show maximum gain, in fact, at about 1 kW per device, which means gain ought to be a bit HIGHER at 1.5 kW than 1 kW for two devices. Since there are two of them in the KPA1500, the compression at 1.5 kW is a bit surprising. (That's about what one would expect from ONE device at 1.5 kW.) Yes, the data sheet curves are for a specific test circuit at 108 MHz, but it's still surprising. On the other hand, anyone who has designed electronics knows to take the published data sheets skeptically. Elecraft has, no doubt, tested lots of them, and knows their REAL characteristics. 73, Scott K9MA -- Scott K9MA k...@sdellington.us __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
I'll have to make some more measurements, but Paul's seem to have much less gain compression than mine. (0.6 vs 1.4 dB from 1 kW to 1.5 kW) That's also closer to the specs for a pair of BLF88XR's. 73, Scott K9MA -- Scott Ellington --- via iPad > On Jun 15, 2018, at 11:24 PM, Paul Baldock wrote: > > I received my KPA-1500 yesterday (#244) and did some linearity tests today > > 14.2MHz, Dummy Load, ATU Bypassed. Using KPA-1500 internal Power Meter. > Continuous carrier. > > 10W drive, Gain = 15.6dB 180W > 15W drive, Gain = 15.8dB > 20W drive, Gain = 15.9dB > 25W drive, Gain = 16.0dB 1.0KW > 30W drive, Gain = 15.9dB > 35W drive, Gain = 15.7dB > 40W drive, Gain = 15.6dB > 43W drive, Gain = 15.4dB 1.5KW > 45W drive, Gain = 15.4dB 1.57KW > > Based on this it look like about .6dB compression at 1.5KW. I think that's > pretty good for an SS Amp. > > I also measured the gain on all the bands at 1.5KW out. Drive varied from 31W > on 80M to 47W on 15M. or 16.8dB to 15.0dB. That amount of variation is rather > disappointing. > > I also noted that the internal power meter is pretty inaccurate at low > levels. For Example at 50W on 20M it reads 43W. Its pretty close above 300W > and right on at 1.5KW where its calibrated. > > I would be interested to see any data that others have collected. > > - Paul KW7Y > > > At 02:26 PM 6/14/2018, K9MA wrote: >> The gain compression I measured, between 1000 and 1500 W on 40 meters, was >> 1.4 dB. I used the K3 and KPA1500 power meters. Factory calibration of the >> KPA1500. >> >> Scott K9MA >> >> -- >> >> Scott Ellington >> >> --- via iPad >> >> > On Jun 14, 2018, at 2:51 PM, Paul Baldock wrote: >> > >> > What you report of compression near the maximum power is certainly true of >> > the amplifiers like the SPE-1.5K that use a single device, but I would >> > have thought this would not be true of the KPA1500 that uses 2 devices. >> > This is the reason I returned my SPE and ordered the KPA. Hopefully the >> > compression is less than 1dB. >> > >> > Has anybody else measured it? >> > >> > - Paul - KW7Y >> > >> > >> > >> > At 02:21 PM 6/9/2018, you wrote: >> >> I recently ran a two-tone test and measured CW power gain. (SN1078) It >> >> doesn't look good. The two-tone waveform shows distinct "flat-topping", >> >> and the power gain drops 25 percent from 1000 to 1500 Watts. My old >> >> 3-500Z amplifier is much better. Has anyone measured IMD or linearity, >> >> or seen any test results? While I'm primarily a CW operator, I'd be very >> >> reluctant to use the amplifier on SSB. 73, Scott K9MA -- Scott K9MA >> >> k...@sdellington.us >> >> __ 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 Message delivered to >> >> p...@paulbaldock.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 >> > Message delivered to k...@sdellington.us __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
I received my KPA-1500 yesterday (#244) and did some linearity tests today 14.2MHz, Dummy Load, ATU Bypassed. Using KPA-1500 internal Power Meter. Continuous carrier. 10W drive, Gain = 15.6dB 180W 15W drive, Gain = 15.8dB 20W drive, Gain = 15.9dB 25W drive, Gain = 16.0dB 1.0KW 30W drive, Gain = 15.9dB 35W drive, Gain = 15.7dB 40W drive, Gain = 15.6dB 43W drive, Gain = 15.4dB 1.5KW 45W drive, Gain = 15.4dB 1.57KW Based on this it look like about .6dB compression at 1.5KW. I think that's pretty good for an SS Amp. I also measured the gain on all the bands at 1.5KW out. Drive varied from 31W on 80M to 47W on 15M. or 16.8dB to 15.0dB. That amount of variation is rather disappointing. I also noted that the internal power meter is pretty inaccurate at low levels. For Example at 50W on 20M it reads 43W. Its pretty close above 300W and right on at 1.5KW where its calibrated. I would be interested to see any data that others have collected. - Paul KW7Y At 02:26 PM 6/14/2018, K9MA wrote: The gain compression I measured, between 1000 and 1500 W on 40 meters, was 1.4 dB. I used the K3 and KPA1500 power meters. Factory calibration of the KPA1500. Scott K9MA -- Scott Ellington --- via iPad > On Jun 14, 2018, at 2:51 PM, Paul Baldock wrote: > > What you report of compression near the maximum power is certainly true of the amplifiers like the SPE-1.5K that use a single device, but I would have thought this would not be true of the KPA1500 that uses 2 devices. This is the reason I returned my SPE and ordered the KPA. Hopefully the compression is less than 1dB. > > Has anybody else measured it? > > - Paul - KW7Y > > > > At 02:21 PM 6/9/2018, you wrote: >> I recently ran a two-tone test and measured CW power gain. (SN1078)Ã It doesn't look good.Ã The two-tone waveform shows distinct "flat-topping", and the power gain drops 25 percent from 1000 to 1500 Watts.Ã My old 3-500Z amplifier is much better.Ã Has anyone measured IMD or linearity, or seen any test results? While I'm primarily a CW operator, I'd be very reluctant to use the amplifier on SSB. 73, Scott K9MA -- Scott K9MA k...@sdellington.us __ 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 Message delivered to p...@paulbaldock.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 > Message delivered to k...@sdellington.us __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
The gain compression I measured, between 1000 and 1500 W on 40 meters, was 1.4 dB. I used the K3 and KPA1500 power meters. Factory calibration of the KPA1500. Scott K9MA -- Scott Ellington --- via iPad > On Jun 14, 2018, at 2:51 PM, Paul Baldock wrote: > > What you report of compression near the maximum power is certainly true of > the amplifiers like the SPE-1.5K that use a single device, but I would have > thought this would not be true of the KPA1500 that uses 2 devices. This is > the reason I returned my SPE and ordered the KPA. Hopefully the compression > is less than 1dB. > > Has anybody else measured it? > > - Paul - KW7Y > > > > At 02:21 PM 6/9/2018, you wrote: >> I recently ran a two-tone test and measured CW power gain. (SN1078) It >> doesn't look good. The two-tone waveform shows distinct "flat-topping", >> and the power gain drops 25 percent from 1000 to 1500 Watts. My old 3-500Z >> amplifier is much better. Has anyone measured IMD or linearity, or seen >> any test results? While I'm primarily a CW operator, I'd be very reluctant >> to use the amplifier on SSB. 73, Scott K9MA -- Scott K9MA >> k...@sdellington.us >> __ 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 Message delivered to p...@paulbaldock.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 > Message delivered to k...@sdellington.us __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
What you report of compression near the maximum power is certainly true of the amplifiers like the SPE-1.5K that use a single device, but I would have thought this would not be true of the KPA1500 that uses 2 devices. This is the reason I returned my SPE and ordered the KPA. Hopefully the compression is less than 1dB. Has anybody else measured it? - Paul - KW7Y At 02:21 PM 6/9/2018, you wrote: I recently ran a two-tone test and measured CW power gain. (SN1078) It doesn't look good. The two-tone waveform shows distinct "flat-topping", and the power gain drops 25 percent from 1000 to 1500 Watts. My old 3-500Z amplifier is much better. Has anyone measured IMD or linearity, or seen any test results? While I'm primarily a CW operator, I'd be very reluctant to use the amplifier on SSB. 73, Scott K9MA -- Scott K9MA k...@sdellington.us __ 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 Message delivered to p...@paulbaldock.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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
On 6/9/2018 2:21 PM, K9MA wrote: While I'm primarily a CW operator, I'd be very reluctant to use the amplifier on SSB. CW is 100% Amplitude Modulation of a carrier by a rectangular wave, so the transitions are rich in harmonics that are heard as clicks, and they WILL excite IM in a non-linear path. 73, Jim K9YC __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
Thank you for posting this. I have been saying it for years on these forums and getting told that I didn't know what I was talking about. Now maybe the naysayers will take note. Wes N7WS On 6/9/2018 6:28 PM, Wayne Burdick wrote: Finally, both the transceiver and amp will vary from band to band somewhat in IMD. You might for example see -40 dBc on one, but in the low 30’s on the other, on a given band. Again, this is typical of all such SS rigs/amps except those running class A or using closed-loop feedback (predistortion). __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
Thanks, Wayne. I'm glad to hear this isn't typical. I sent a report to tech support with all the details. I'll call later next week, as I'll be out of town with the KX2 until Thursday. 73, Scott K9MA -- Scott Ellington --- via iPad > On Jun 9, 2018, at 8:28 PM, Wayne Burdick wrote: > > Scott, > > I’m not sure how you’re doing the test, but this is definitely not > characteristic. > > We test every amp for IMD, and we see an average of about -35 dBc (3rd order, > ARRL method) across all bands. This is state of the art for an LDMOS deign > running class AB. Other SS amps using similar designs have have similar > performance. > > Any amp’s gain levels off as it approaches peak power (ie, is slightly in > compression). But it should not be flat-topping unless it’s over driven or is > starved for supply current/voltage. > > Finally, both the transceiver and amp will vary from band to band somewhat in > IMD. You might for example see -40 dBc on one, but in the low 30’s on the > other, on a given band. Again, this is typical of all such SS rigs/amps > except those running class A or using closed-loop feedback (predistortion). > > Please call Monday to discuss your test method with one of our technical > staff. > > 73, > Wayne > N6KR > > > > http://www.elecraft.com > >> On Jun 9, 2018, at 2:21 PM, K9MA wrote: >> >> I recently ran a two-tone test and measured CW power gain. (SN1078) It >> doesn't look good. The two-tone waveform shows distinct "flat-topping", and >> the power gain drops 25 percent from 1000 to 1500 Watts. My old 3-500Z >> amplifier is much better. Has anyone measured IMD or linearity, or seen any >> test results? >> >> While I'm primarily a CW operator, I'd be very reluctant to use the >> amplifier on SSB. >> >> 73, >> >> Scott K9MA >> >> -- >> Scott K9MA >> >> k...@sdellington.us >> >> __ >> 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 >> Message delivered to n...@elecraft.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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
Scott, I don’t know if this helps much but several of the locals have constructed BLF-188 amps (singles and pairs) in the past two years. The W7, Israeli and Russian boards were used and they all suffered the same fate in various degrees. They would cease being very linear at about 75% of their CW output. Careful selection of bias and feedback levels would allow some improvement but in none of the cases were the devices even close to acceptable IMD wise at their data sheet output levels. The only one that am aware of that worked well was a W8 friend who is driving it (EB-104 water cooled Russian amplifier) with an Anan and used Pure Signal to effectively clean it up. On all of the others when the output came up to the target level you could immediately start seeing them in the opposite sideband. All of the data sheets that we saw at the time talked about CW/FM applications and none provided specs for SSB linear service. These have been my observations of the BLF-188 amps. Very 73 - Mike - K9JRI > On Jun 9, 2018, at 9:08 PM, K9MA wrote: > > I did look at the K3 output, and it's much, much better than the KPA1500 > output. I also checked that the KPA1500 supply voltage was not dropping > much: 53 V in standby, 52 V at 1500 W. > > 73, > Scott K9MA > > -- > > Scott Ellington > > --- via iPad > >> On Jun 9, 2018, at 7:26 PM, Wes Stewart wrote: >> >> I don't have a KPA1500 or enough power attenuators to test my KPA500, but I >> have spent many dozens of hours looking at TX IMD on my two K3s. >> >> I will simply say, if you haven't already, check the IMD of the bare K3 >> before blaming the KPA1500. Garbage in, garbage out. That of course doesn't >> pardon the KPA for dropping gain. >> >> Wes N7WS >> >> >>> On 6/9/2018 2:21 PM, K9MA wrote: >>> I recently ran a two-tone test and measured CW power gain. (SN1078) It >>> doesn't look good. The two-tone waveform shows distinct "flat-topping", >>> and the power gain drops 25 percent from 1000 to 1500 Watts. My old 3-500Z >>> amplifier is much better. Has anyone measured IMD or linearity, or seen >>> any test results? >>> >>> While I'm primarily a CW operator, I'd be very reluctant to use the >>> amplifier on SSB. >>> >>> 73, >>> >>> Scott K9MA >>> >> >> __ >> 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 >> Message delivered to k...@sdellington.us > > __ > 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 > Message delivered to k9...@mac.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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
Scott, I’m not sure how you’re doing the test, but this is definitely not characteristic. We test every amp for IMD, and we see an average of about -35 dBc (3rd order, ARRL method) across all bands. This is state of the art for an LDMOS deign running class AB. Other SS amps using similar designs have have similar performance. Any amp’s gain levels off as it approaches peak power (ie, is slightly in compression). But it should not be flat-topping unless it’s over driven or is starved for supply current/voltage. Finally, both the transceiver and amp will vary from band to band somewhat in IMD. You might for example see -40 dBc on one, but in the low 30’s on the other, on a given band. Again, this is typical of all such SS rigs/amps except those running class A or using closed-loop feedback (predistortion). Please call Monday to discuss your test method with one of our technical staff. 73, Wayne N6KR http://www.elecraft.com > On Jun 9, 2018, at 2:21 PM, K9MA wrote: > > I recently ran a two-tone test and measured CW power gain. (SN1078) It > doesn't look good. The two-tone waveform shows distinct "flat-topping", and > the power gain drops 25 percent from 1000 to 1500 Watts. My old 3-500Z > amplifier is much better. Has anyone measured IMD or linearity, or seen any > test results? > > While I'm primarily a CW operator, I'd be very reluctant to use the amplifier > on SSB. > > 73, > > Scott K9MA > > -- > Scott K9MA > > k...@sdellington.us > > __ > 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 > Message delivered to n...@elecraft.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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
I did look at the K3 output, and it's much, much better than the KPA1500 output. I also checked that the KPA1500 supply voltage was not dropping much: 53 V in standby, 52 V at 1500 W. 73, Scott K9MA -- Scott Ellington --- via iPad > On Jun 9, 2018, at 7:26 PM, Wes Stewart wrote: > > I don't have a KPA1500 or enough power attenuators to test my KPA500, but I > have spent many dozens of hours looking at TX IMD on my two K3s. > > I will simply say, if you haven't already, check the IMD of the bare K3 > before blaming the KPA1500. Garbage in, garbage out. That of course doesn't > pardon the KPA for dropping gain. > > Wes N7WS > > >> On 6/9/2018 2:21 PM, K9MA wrote: >> I recently ran a two-tone test and measured CW power gain. (SN1078) It >> doesn't look good. The two-tone waveform shows distinct "flat-topping", and >> the power gain drops 25 percent from 1000 to 1500 Watts. My old 3-500Z >> amplifier is much better. Has anyone measured IMD or linearity, or seen any >> test results? >> >> While I'm primarily a CW operator, I'd be very reluctant to use the >> amplifier on SSB. >> >> 73, >> >> Scott K9MA >> > > __ > 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 > Message delivered to k...@sdellington.us __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA1500 Linearity
I don't have a KPA1500 or enough power attenuators to test my KPA500, but I have spent many dozens of hours looking at TX IMD on my two K3s. I will simply say, if you haven't already, check the IMD of the bare K3 before blaming the KPA1500. Garbage in, garbage out. That of course doesn't pardon the KPA for dropping gain. Wes N7WS On 6/9/2018 2:21 PM, K9MA wrote: I recently ran a two-tone test and measured CW power gain. (SN1078) It doesn't look good. The two-tone waveform shows distinct "flat-topping", and the power gain drops 25 percent from 1000 to 1500 Watts. My old 3-500Z amplifier is much better. Has anyone measured IMD or linearity, or seen any test results? While I'm primarily a CW operator, I'd be very reluctant to use the amplifier on SSB. 73, Scott K9MA __ 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 Message delivered to arch...@mail-archive.com
[Elecraft] KPA1500 Linearity
I recently ran a two-tone test and measured CW power gain. (SN1078) It doesn't look good. The two-tone waveform shows distinct "flat-topping", and the power gain drops 25 percent from 1000 to 1500 Watts. My old 3-500Z amplifier is much better. Has anyone measured IMD or linearity, or seen any test results? While I'm primarily a CW operator, I'd be very reluctant to use the amplifier on SSB. 73, Scott K9MA -- Scott K9MA k...@sdellington.us __ 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 Message delivered to arch...@mail-archive.com
