K3S QST Article
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The November issue of QST arrived in the mail today. Nice article about the K3S, in case anyone hasn’t yet seen it.
Ted, KN1CBR ______________________________________________________________ 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 Message delivered to [hidden email] |
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Thank you for noticing :)
73, Wayne N6KR On Oct 12, 2016, at 8:41 PM, "Dauer, Edward" <[hidden email]> wrote: > The November issue of QST arrived in the mail today. Nice article about the K3S, in case anyone hasn’t yet seen it. > > Ted, KN1CBR ______________________________________________________________ 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 Message delivered to [hidden email] |
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Hi,
Very good review - for the most part. I am concerned about the transmit IMD results mentioned only in a side bar "Lab Notes: ..." on page 50. Initially the transmit IMD in the original review sample was less than stellar, but eventually got resolved by Elecraft submitting a new review sample with KPA3A rev C4 and KLPA3 rev B installed. How can I tell if my relatively new K3S ser# 10480 has the new modules installed? If they aren't, is this a warranty repair? AB2TC - Knut |
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I have not seen my QST yet. I think the mailman reads it first. But you ask an
excellent question. On 10/13/2016 2:25 PM, ab2tc wrote: > Hi, > > Very good review - for the most part. > > I am concerned about the transmit IMD results mentioned only in a side bar > "Lab Notes: ..." on page 50. Initially the transmit IMD in the original > review sample was less than stellar, but eventually got resolved by Elecraft > submitting a new review sample with KPA3A rev C4 and KLPA3 rev B installed. > How can I tell if my relatively new K3S ser# 10480 has the new modules > installed? If they aren't, is this a warranty repair? > > AB2TC - Knut > ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by ab2tc
Good question that I would like to know the answer to.
Leroy AB7CE -----Original Message----- From: ab2tc Sent: Thursday, October 13, 2016 3:25 PM To: [hidden email] Subject: Re: [Elecraft] K3S QST Article Hi, Very good review - for the most part. I am concerned about the transmit IMD results mentioned only in a side bar "Lab Notes: ..." on page 50. Initially the transmit IMD in the original review sample was less than stellar, but eventually got resolved by Elecraft submitting a new review sample with KPA3A rev C4 and KLPA3 rev B installed. How can I tell if my relatively new K3S ser# 10480 has the new modules installed? If they aren't, is this a warranty repair? AB2TC - Knut -- View this message in context: http://elecraft.365791.n2.nabble.com/K3S-QST-Article-tp7623295p7623325.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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by Wes Stewart-2
Hi Wes,
You can read it online. I received an Email link from ARRL to my online copy. AB2TC - Knut
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Hi Knut,
Yes, I get a notification about the digital issue, but I prefer to read the paper copy, so I wait. It did come yesterday so I've seen it now. Wes On 10/13/2016 5:35 PM, ab2tc wrote: > Hi Wes, > > You can read it online. I received an Email link from ARRL to my online > copy. > > AB2TC - Knut > > ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by ab2tc
I was not surprised to see a comment about the Tx IMDs in the QST article. One of the first problems I encountered with my new K3s/10 was poor Tx IMD performance. What I observed was flat topping that started at about 5W, and progressively got worse as the power was increased. The distortion was so bad at 10W, the envelope looked more like a squarewave than a two tone signal, and the 3rd order products were down only -18 dBc. After several months of working with Wayne, Rene, and the designer of the KLPA3A amplifier, replacing the KLPA3A three times, and sending the radio to the factory, the problem was reduced, but I still don't see better than -28 dBc at 10W out. Not wanting to send the radio in to the factory a second time, I decided to just live with the performance.
The transmit signal generation in the K3s is a complex process based around the internal computer. Signal quality is affected by ALC, transmit power level, configuration settings, and the transmit power CAL, however, from all of the testing that I did, the signal going into the KLPA3A was very clean (-40 dBc). It is also important to note that Elecraft's approach to distortion management includes spreading the energy in the distortion out spectrally by the use of pre-distortion. This results in 5th, 7th, 9th,... order products being higher compared to some radios, as noted in the QST article. The QST article indicated that both the KLPA3A and the KPA3A have been modified to address the Tx IMD problem. I am hopeful that at some point Elecraft will offer some info/options that will allow us to bring the unmodified radios up to the performance shown in the QST article Bill N0CU |
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Based upon your experience and understanding of the issue, would an original K3 (not K3s) with the new synths have better TX IMD? In other words, is the poor TX IMD of the K3s a function of some part of the rig not associated with the new synths? Dave AB7E On 10/14/2016 9:06 AM, Bill Leonard N0CU wrote: > I was not surprised to see a comment about the Tx IMDs in the QST article. > One of the first problems I encountered with my new K3s/10 was poor Tx IMD > performance. What I observed was flat topping that started at about 5W, and > progressively got worse as the power was increased. The distortion was so > bad at 10W, the envelope looked more like a squarewave than a two tone > signal, and the 3rd order products were down only -18 dBc. After several > months of working with Wayne, Rene, and the designer of the KLPA3A > amplifier, replacing the KLPA3A three times, and sending the radio to the > factory, the problem was reduced, but I still don't see better than -28 dBc > at 10W out. Not wanting to send the radio in to the factory a second time, I > decided to just live with the performance. > > The transmit signal generation in the K3s is a complex process based around > the internal computer. Signal quality is affected by ALC, transmit power > level, configuration settings, and the transmit power CAL, however, from all > of the testing that I did, the signal going into the KLPA3A was very clean > (-40 dBc). It is also important to note that Elecraft's approach to > distortion management includes spreading the energy in the distortion out > spectrally by the use of pre-distortion. This results in 5th, 7th, 9th,... > order products being higher compared to some radios, as noted in the QST > article. > > The QST article indicated that both the KLPA3A and the KPA3A have been > modified to address the Tx IMD problem. I am hopeful that at some point > Elecraft will offer some info/options that will allow us to bring the > unmodified radios up to the performance shown in the QST article > > Bill N0CU > > > > -- > View this message in context: http://elecraft.365791.n2.nabble.com/K3S-QST-Article-tp7623295p7623355.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:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by Wes Stewart-2
Hi all,
I, too. prefer the paper copy, but the mention of a K3S review got me too intrigued, so I had to read it online. As for the other comments in this thread, I find this situation more than a little worrisome and certainly an official Elecraft response is hoped for. Are the updates being tested by the ARRL and published as their final findings in their performance tables even into production yet? AB2TC - Knut
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In reply to this post by David Gilbert
I would not expect the synthesizer (old or new) to be a contributor the IMD issue. Hopefully someone will correct me if that is a bad assumption. To me, the primary issue appears to be the linearity of the two RF power amplifiers.
During the course of my troubleshooting, I noticed that a number of changes were made to the original KLPA3 in the process of getting to the new KLPA3A design. I would be interested in knowing how the IMD performance of the original design compares to the new KLPA3A design. Bill N0CU |
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In reply to this post by ab2tc
> Based upon your experience and understanding of the issue, would an original K3 (not K3s) with the new synths have better TX IMD? In other words, is the poor TX IMD of the K3s a function of some part of the rig not associated with the new synths?
> > Dave AB7E Hi all, This has nothing to do with the new synthesizer. Normally, the K3S (or K3) has worst-case TX 3rd-order IMD in the vicinity of -30 dBc (ARRL method) at rated power (10 W/100 W +/- 1 dB on most bands; see specs for exceptions). Nearly all other 12-V-capable transceivers are in this same range, because they all use approximately the same circuitry and PA devices. We have made changes in K3S production that improve average IMD performance at both low and high power levels by as much as 3 dB. We will make these changes free of charge on any K3S returned to the factory for this purpose, whether or not it is still in the warranty period. The only charge would be for return shipping. The changes were phased in at the following serial numbers: KPA3A (100 W PA option): Factory assembled, #10852 Kit, #10864 LPA (10 W module): Factory assembled, #10920 Kit, #10939 Please email [hidden email] if you have any further questions. 73, Wayne N6KR ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by Bill Leonard N0CU
The cause for this is the use of 12V finals. It would be much improved
by moving to 24 or 50V finals. Move the /K3s II/ to 50V finals, say a pair of MRF 150's, limited to 150 or 200W max output. Design/Sell an outboard 50V switching supply capable of 15-20A continuous current, with a 10A 12V switcher built in for the rest of the radio. On 10/14/2016 1:33 PM, Bill Leonard N0CU wrote: > I would not expect the synthesizer (old or new) to be a contributor the IMD > issue. Hopefully someone will correct me if that is a bad assumption. To me, > the primary issue appears to be the linearity of the two RF power > amplifiers. > > -- R. Kevin Stover AC0H ARRL FISTS #11993 SKCC #215 NAQCC #3441 --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ______________________________________________________________ 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 Message delivered to [hidden email] |
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Or, we could all run 32S-3 transmitters and listen on our whiz/bang SDR.
So far, they're about the cleanest 100 watt transmitter reasonably available. 73, Charlie k3ICH -----Original Message----- From: Elecraft [mailto:[hidden email]] On Behalf Of Kevin Sent: Friday, October 14, 2016 8:14 PM To: [hidden email] Subject: Re: [Elecraft] K3S QST Article The cause for this is the use of 12V finals. It would be much improved by moving to 24 or 50V finals. Move the /K3s II/ to 50V finals, say a pair of MRF 150's, limited to 150 or 200W max output. Design/Sell an outboard 50V switching supply capable of 15-20A continuous current, with a 10A 12V switcher built in for the rest of the radio. ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by kstover
Yaesu FT-990, 12V finals
3rd order TX IMD -38dB ARRL Review 11/91 ARRL heaped glowing praise upon this rig way back in 1991 for its Tx IMD performance. So, what was Yaesu's secret, and why haven't manufacturers figured it out and capitalized on it ever since? Dave Hachadorian, K6LL Yuma, Arizona -----Original Message----- From: Kevin Sent: Friday, October 14, 2016 5:14 PM To: [hidden email] Subject: Re: [Elecraft] K3S QST Article The cause for this is the use of 12V finals. It would be much improved by moving to 24 or 50V finals. Move the /K3s II/ to 50V finals, say a pair of MRF 150's, limited to 150 or 200W max output. Design/Sell an outboard 50V switching supply capable of 15-20A continuous current, with a 10A 12V switcher built in for the rest of the radio. On 10/14/2016 1:33 PM, Bill Leonard N0CU wrote: > I would not expect the synthesizer (old or new) to be a > contributor the IMD > issue. Hopefully someone will correct me if that is a bad > assumption. To me, > the primary issue appears to be the linearity of the two RF > power > amplifiers. > > -- R. Kevin Stover AC0H ARRL FISTS #11993 SKCC #215 NAQCC #3441 --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ______________________________________________________________ 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 Message delivered to [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by Edward A. Dauer
OK. I purchased the K3/10 in 2010 which is able to output up to 12w.
Is the low power amp any better at IMD, or subject to the same limitations because its 12v transistors? I bought the KXPA-100 last year. Would it be any better than the KPA3 or KPA3A? 3rd-order IMD in the vicinity of -30 dBc is about what I have read for specs my many 12v power devices. I bought the new synth because I understood it would improve Rx performance (haven't installed them yet main & sub Rx). Also for K3 use at 630m. Would running the K3/10 at 5w driving a linear amp be lower in IMD? The amp uses 50v devices and made for TV which has greater linearity specs than SSB. I am also running it at about 60% full output on 6m. 73, Ed - KL7UW http://www.kl7uw.com "Kits made by KL7UW" Dubus Mag business: [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by Dave Hachadorian-2
Without too much elaboration let's just say that I discovered this problem long
before ARRL did. (S/N 10020) I can tell you that my measurements show that IMD varies with Vcc (Vdd), drive level, power output and frequency. This latter parameter is, as best as I can determine, inexplicable by anyone, including the manufacturers of the transistors. Initially, I compared my shiny new K3S to my tired old, unmodified K3. At the original test frequency, 3.8 MHz the K3 had much lower IMD that the K3S under otherwise the same test conditions. Moving up to 14 MHz the situation reversed. Each of these radios had a different "sweet spot," neither of which was representative of the general case. If a testing entity happens to test at only one frequency and reports the results as typical then you get a false sense of the general performance. Wes, N7WS On 10/14/2016 8:03 PM, Dave Hachadorian wrote: > Yaesu FT-990, 12V finals > 3rd order TX IMD -38dB > ARRL Review 11/91 > > ARRL heaped glowing praise upon this rig way back in 1991 for its > Tx IMD performance. So, what was Yaesu's secret, and why haven't > manufacturers figured it out and capitalized on it ever since? > > Dave Hachadorian, K6LL > Yuma, Arizona > > > -----Original Message----- From: Kevin > Sent: Friday, October 14, 2016 5:14 PM > To: [hidden email] > Subject: Re: [Elecraft] K3S QST Article > > The cause for this is the use of 12V finals. It would be much > improved > by moving to 24 or 50V finals. > > Move the /K3s II/ to 50V finals, say a pair of MRF 150's, limited > to 150 > or 200W max output. Design/Sell an outboard 50V switching supply > capable > of 15-20A continuous current, with a 10A 12V switcher built in > for the > rest of the radio. > > > On 10/14/2016 1:33 PM, Bill Leonard N0CU wrote: >> I would not expect the synthesizer (old or new) to be a >> contributor the IMD >> issue. Hopefully someone will correct me if that is a bad >> assumption. To me, >> the primary issue appears to be the linearity of the two RF >> power >> amplifiers. >> >> > ______________________________________________________________ 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 Message delivered to [hidden email] |
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The improvements we made this year (referenced in my previous posting) bring up both worst-case and average performance of the K3S on all bands, at all power levels.
Regarding the Yaesu radio that hit -38 dBc worst-case using the same PA topology: luck of the draw. There are many factors, including things as esoteric as the quality of the ferrite in the output transformers. We've measured similar rigs from all major manufacturers that were right around -30. In addition, many radios will not hit 100 W on all bands, even at 14 V. 73, Wayne N6KR On Oct 14, 2016, at 9:30 PM, Wes Stewart <[hidden email]> wrote: > Without too much elaboration let's just say that I discovered this problem long before ARRL did. (S/N 10020) > > I can tell you that my measurements show that IMD varies with Vcc (Vdd), drive level, power output and frequency…. ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by Edward R Cole
My experience suggests that running the low power amp in a K3(S) above 10W is a
disaster. In a K3(S)/100 the HPA isn't activated until above 12W. IMHO, again based only on my measurements of my K3 and my K3S (before mods), I would recommend that Elecraft change firmware to set the max power out at 10W (LP) and switch in the KPA100 above 10W, not 12. On 10/14/2016 9:17 PM, Edward R Cole wrote: > OK. I purchased the K3/10 in 2010 which is able to output up to 12w. > > Is the low power amp any better at IMD, or subject to the same limitations > because its 12v transistors? > I bought the KXPA-100 last year. Would it be any better than the KPA3 or > KPA3A? 3rd-order IMD in the vicinity of -30 dBc is about what I have read for > specs my many 12v power devices. > > I bought the new synth because I understood it would improve Rx performance > (haven't installed them yet main & sub Rx). Also for K3 use at 630m. > > Would running the K3/10 at 5w driving a linear amp be lower in IMD? The amp > uses 50v devices and made for TV which has greater linearity specs than SSB. I > am also running it at about 60% full output on 6m. > > 73, Ed - KL7UW > http://www.kl7uw.com > "Kits made by KL7UW" > Dubus Mag business: > [hidden email] ______________________________________________________________ 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 Message delivered to [hidden email] |
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In reply to this post by Dave Hachadorian-2
Yaesu's secret was the ARRL. Unless things have changed they test at one
frequency and assume the other bands produce the same results. I'll reverse the question, what has Yaesu done to rigs since 1991 that they can't reproduce those numbers? On 10/14/2016 10:03 PM, Dave Hachadorian wrote: > Yaesu FT-990, 12V finals > 3rd order TX IMD -38dB > ARRL Review 11/91 > > ARRL heaped glowing praise upon this rig way back in 1991 for its > Tx IMD performance. So, what was Yaesu's secret, and why haven't > manufacturers figured it out and capitalized on it ever since? > > Dave Hachadorian, K6LL > Yuma, Arizona > > > -----Original Message----- From: Kevin > Sent: Friday, October 14, 2016 5:14 PM > To: [hidden email] > Subject: Re: [Elecraft] K3S QST Article > > The cause for this is the use of 12V finals. It would be much > improved > by moving to 24 or 50V finals. > > Move the /K3s II/ to 50V finals, say a pair of MRF 150's, limited > to 150 > or 200W max output. Design/Sell an outboard 50V switching supply > capable > of 15-20A continuous current, with a 10A 12V switcher built in > for the > rest of the radio. > > > On 10/14/2016 1:33 PM, Bill Leonard N0CU wrote: >> I would not expect the synthesizer (old or new) to be a >> contributor the IMD >> issue. Hopefully someone will correct me if that is a bad >> assumption. To me, >> the primary issue appears to be the linearity of the two RF >> power >> amplifiers. >> >> > -- R. Kevin Stover AC0H ARRL FISTS #11993 SKCC #215 NAQCC #3441 --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ______________________________________________________________ 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 Message delivered to [hidden email] |
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