Re: [Elecraft] KPA-1500 ATU not working well
I'm not clear whether you are talking about the SWR before or after the tuner, but efficiency is determined by the load seen by the PA, which has two degrees of freedom (reactance and resistance), both of which can vary either side of the ideal. SWR reduces this to a single variable, that doesn't even respect the sign of the deviation from the ideal load. That means that efficiency may even be better than the nominal efficiency at a particular SWR, whereas that same SWR can also produce a lowered efficiency. (Similarly, an SWR may destroy a PA or be safe, depending on the fine details.) In particular, a higher load resistance may result in a higher efficiency, at the expense of a lower maximum output. There is actually a K2 build option, that winds the output transformer to impose a higher load resistance, in order give better efficiencies at low powers. Tuning across the band will change at least the reactance component of the load on the PA. Also, if input SWR isn't 1:1, I think you will find that the measured forward power doesn't reflect what is actually available to go out through the antenna. Whilst some of it will circulate back and forth and eventually make its way out in the right direction, some will also get absorbed by the PA. On 22/06/18 20:36, Paul Baldock wrote: I have found that if the KPA1500 is feeding a largish SWR (like 1.5:1 as you suggest) then the drive power required to maintain a constant output will vary significantly as you tune across a band. This means you have to keep adjusting the power control within a single band. This appears not to occur if the SWR is 1.1:1 or better. I don't know, but I would guess a solid state untuned amplifier efficiency is better into a 1:1 SWR than a 1:5:1. This could lead to the dreaded more fan noise. __ 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] KPA-1500 ATU not working well
Can we change subject matter. Min is on the way and this is way to freakey!!! 73, Bill K9YEQ https://wrj-tech.com/ -Original Message- From: elecraft-boun...@mailman.qth.net On Behalf Of John Oppenheimer Sent: Friday, June 22, 2018 5:27 PM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] KPA-1500 ATU not working well Here is a picture and some plot images: http://www.kn5l.net/Elecraft/CP1/ Not super accurate 60 and 100 Ohm loads, but provides an insight of the coupler operation. John KN5L On 06/22/2018 04:15 PM, Wes Stewart wrote: > I don't quite understand your methodology but there is one, apparently > little known caveat with the use of the "Elecraft" coupler topology. > AFAIK, this was first used by John Grebenkemper, KI6WX, in his Tandem > Match, described in QST, January 1987. > > Paul Kiciak, N2PK, mentions in his paper, "An HF In-Line Return Loss > And Power Meter", that this coupler suffers from poor input match at lower > frequencies. > So the SWR meter has high SWR! > > If the CP1 wasn't so expensive, I'd buy one just to measure it. __ 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...@live.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] KPA-1500 ATU not working well
Hi John, Well if a picture is worth a thousand words a graph is worth at least 10,000. THANKS for the posting! 73, Bob K2TK ex KN2TKR (1956) & K2TKR On 6/22/2018 6:27 PM, John Oppenheimer wrote: Here is a picture and some plot images: http://www.kn5l.net/Elecraft/CP1/ Not super accurate 60 and 100 Ohm loads, but provides an insight of the coupler operation. John KN5L __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] KPA-1500 ATU not working well
Offhand, since they are adamantly opposed to using operational ALC, I could see incorporating a "1500 W" gain calibration, as they do with K3s. They could read the output power at several frequencies per band and save the gain settings. This assumes they have enough memory in the K3 to save the values. Of course fixing the root cause would be better. Wes N7WS On 6/22/2018 2:31 PM, K9MA wrote: My observation , also. Another approach would be for automatic drive adjustment, or ALC that worked. The latter, I know, is very difficult to do with an amp. Scott K9MA -- Scott Ellington --- via iPad On Jun 22, 2018, at 2:36 PM, Paul Baldock wrote: I have found that if the KPA1500 is feeding a largish SWR (like 1.5:1 as you suggest) then the drive power required to maintain a constant output will vary significantly as you tune across a band. This means you have to keep adjusting the power control within a single band. This appears not to occur if the SWR is 1.1:1 or better. __ 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] KPA-1500 ATU not working well
Here is a picture and some plot images: http://www.kn5l.net/Elecraft/CP1/ Not super accurate 60 and 100 Ohm loads, but provides an insight of the coupler operation. John KN5L On 06/22/2018 04:15 PM, Wes Stewart wrote: > I don't quite understand your methodology but there is one, apparently little > known caveat with the use of the "Elecraft" coupler topology. AFAIK, this > was > first used by John Grebenkemper, KI6WX, in his Tandem Match, described in > QST, > January 1987. > > Paul Kiciak, N2PK, mentions in his paper, "An HF In-Line Return Loss And > Power > Meter", that this coupler suffers from poor input match at lower frequencies. > > So the SWR meter has high SWR! > > If the CP1 wasn't so expensive, I'd buy one just to measure it. __ 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] KPA-1500 ATU not working well
Wes, so well put. The expectations expressed don't include a whole new set of variables when dealing with full power. The good thing: this list may help those challenged to get help to figure out their issues. I can't wait to get mine on the air! 72 & 73, Bill K9YEQ FT’er for K2, KX1, KX3, KXPA100, KAT500, W2, etc. -Original Message- From: elecraft-boun...@mailman.qth.net On Behalf Of Wes Stewart Sent: Friday, June 22, 2018 3:45 PM To: Paul Baldock ; elecraft@mailman.qth.net Subject: Re: [Elecraft] KPA-1500 ATU not working well OK, note my qualifier, "If". If there are other detrimental issues with greater load mismatch then they might need to be addressed. Unfortunately, Elecraft doesn't specify a load requirement for rated output. Gain ripple that you observe is possibly a reflection (no pun intended) of the LPFs rather than the intrinsic performance of the transistors, although as I have reported elsewhere K3S IMD is frequency sensitive, but not overly so within a band. One point I would like to make is that guys who wring their hands because the SWR meters on the K3, KAT500 and KPAs all read differently should lighten up. There are reasons why this can be without there being product defects. Wes N7WS .On 6/22/2018 12:36 PM, Paul Baldock wrote: > I have found that if the KPA1500 is feeding a largish SWR (like 1.5:1 > as you > suggest) then the drive power required to maintain a constant output > will vary significantly as you tune across a band. This means you have > to keep adjusting the power control within a single band. This appears > not to occur if the SWR is 1.1:1 or better. > > I don't know, but I would guess a solid state untuned amplifier > efficiency is better into a 1:1 SWR than a 1:5:1. This could lead to > the dreaded more fan noise. > > By the way by suggesting 1.0:1. I did not mean exactly > 1.000:1. I tired to infer 1 digit resolution/accuracy. > > - Paul KW7Y > > > At 11:11 AM 6/22/2018, Wes Stewart wrote: >> I do not, and probably never will, have a KPA1500. I do have a >> KPA500 and >> KAT500 so I think I can comment. In my opinion, the function of >> these tuners is to provide a match into which the amp can deliver >> full power. If >> 1.5:1 does this, then that's good enough in my book. Furthermore, a >> better match might entail higher tuner losses. So why worry about >> it? Another thing; a 1.0:1 SWR infers infinite return loss. To >> measure infinite return loss, you need a directional coupler with >> infinite directivity or some mathematical correction derived from >> very well known calibration standards and no other errors, So maybe >> you say, 1.0:1 can't be measured (you would be correct), let's shoot >> for 1.22:1.  That's a return loss of ~20 dB. Now I have no idea >> of what the directivity of the coupler is in the KAT500 or >> KPA1500 but considering it has to work from 1.8 to 54 MHz and to keep >> the numbers easy, 20 dB wouldn't be unreasonable. (Note: I'm only >> considering the directivity error, there are several others, internal >> mismatches, frequency tracking, detector non-linearities, etc.) If we >> measure a load with 20 dB RL using a directional coupler with 20 dB >> directivity the answer can be anywhere between infinity to 14 dB. >> (Full cancellation of the two reflection coefficients to the sum of >> the reflection coefficients) In SWR terms, a >> 1.22:1 load can measure anywhere between 1.0:1 and 1.5:1. A >> "perfect" load will measure 1.22:1. Folks, these things aren't >> laboratory instruments and until Elecraft builds in vector network >> analyzers with full error correction this is what we get. Wes N7WS >> On 6/21/2018 11:17 PM, Paul Baldock wrote: > First let me say that >> other than some issues with the ATU, I am after a week >> > of use, very happy with the KPA1500. > > So here's the ATU issues: >> > > > I >> find that the ATU very rarely will learn a setting to get the SWR >> below > >> 1.2:1 on any band. I can usually tweak it down to 1.0:1 using the >> Utility > Program. And yes, before anybody asks, I have ATU STOP >> TUNE and the ATU > BYPASS set at 1.0:1. > > On 6M into a perfect load >> (laboratory quality to >> 8GHz) with the ATU bypassed, > the internal SWR meter reads 1.4:1 I >> would have expected it to be 1.0:1, but > Elecraft tell me it is >> normal. So the ATU on 6M will have to tune out what is > left when >> the 1.4:1 internal mismatch sees your external antenna mismatch. > >> Maybe this is contributing to your problem. Try adding a qua
Re: [Elecraft] KPA-1500 ATU not working well
My observation , also. Another approach would be for automatic drive adjustment, or ALC that worked. The latter, I know, is very difficult to do with an amp. Scott K9MA -- Scott Ellington --- via iPad > On Jun 22, 2018, at 2:36 PM, Paul Baldock wrote: > > I have found that if the KPA1500 is feeding a largish SWR (like 1.5:1 as you > suggest) then the drive power required to maintain a constant output will > vary significantly as you tune across a band. This means you have to keep > adjusting the power control within a single band. This appears not to occur > if the SWR is 1.1:1 or better. __ 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] KPA-1500 ATU not working well
I don't quite understand your methodology but there is one, apparently little known caveat with the use of the "Elecraft" coupler topology. AFAIK, this was first used by John Grebenkemper, KI6WX, in his Tandem Match, described in QST, January 1987. Paul Kiciak, N2PK, mentions in his paper, "An HF In-Line Return Loss And Power Meter", that this coupler suffers from poor input match at lower frequencies. So the SWR meter has high SWR! If the CP1 wasn't so expensive, I'd buy one just to measure it. Wes N7WS On 6/22/2018 1:20 PM, John Oppenheimer wrote: Putting the Elecraft CP1 through the paces with a 2 port VNA can be enlightening. The CP1 seems to be representative of Elecraft directional couplers across the line. There's a picture of the W2 high power HF coupler in the manual, it's just larger cores. Sweeping a 20 dB CP1 across the band with a VNWA with a 60 Ohm load, 1.2:1, results with a relative constant -40 dB reflected gain and a -20 forward gain. A closer match to 50 Ohm fall's apart with a wide -40 db to -70 dB dip at 7 MHz reflected across the band at 50 Ohm. I can agree, 1.2 : 1 is about the limit. John KN5L On 06/22/2018 01:11 PM, Wes Stewart wrote: That's a return loss of ~20 dB. Now I have no idea of what the directivity of the coupler is in the KAT500 or KPA1500 but considering it has to work from 1.8 to 54 MHz and to keep the numbers easy, 20 dB wouldn't be unreasonable. __ 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] KPA-1500 ATU not working well
OK, note my qualifier, "If". If there are other detrimental issues with greater load mismatch then they might need to be addressed. Unfortunately, Elecraft doesn't specify a load requirement for rated output. Gain ripple that you observe is possibly a reflection (no pun intended) of the LPFs rather than the intrinsic performance of the transistors, although as I have reported elsewhere K3S IMD is frequency sensitive, but not overly so within a band. One point I would like to make is that guys who wring their hands because the SWR meters on the K3, KAT500 and KPAs all read differently should lighten up. There are reasons why this can be without there being product defects. Wes N7WS .On 6/22/2018 12:36 PM, Paul Baldock wrote: I have found that if the KPA1500 is feeding a largish SWR (like 1.5:1 as you suggest) then the drive power required to maintain a constant output will vary significantly as you tune across a band. This means you have to keep adjusting the power control within a single band. This appears not to occur if the SWR is 1.1:1 or better. I don't know, but I would guess a solid state untuned amplifier efficiency is better into a 1:1 SWR than a 1:5:1. This could lead to the dreaded more fan noise. By the way by suggesting 1.0:1. I did not mean exactly 1.000:1. I tired to infer 1 digit resolution/accuracy. - Paul KW7Y At 11:11 AM 6/22/2018, Wes Stewart wrote: I do not, and probably never will, have a KPA1500. I do have a KPA500 and KAT500 so I think I can comment. In my opinion, the function of these tuners is to provide a match into which the amp can deliver full power. If 1.5:1 does this, then that's good enough in my book. Furthermore, a better match might entail higher tuner losses. So why worry about it? Another thing; a 1.0:1 SWR infers infinite return loss. To measure infinite return loss, you need a directional coupler with infinite directivity or some mathematical correction derived from very well known calibration standards and no other errors, So maybe you say, 1.0:1 can't be measured (you would be correct), let's shoot for 1.22:1.  That's a return loss of ~20 dB. Now I have no idea of what the directivity of the coupler is in the KAT500 or KPA1500 but considering it has to work from 1.8 to 54 MHz and to keep the numbers easy, 20 dB wouldn't be unreasonable. (Note: I'm only considering the directivity error, there are several others, internal mismatches, frequency tracking, detector non-linearities, etc.) If we measure a load with 20 dB RL using a directional coupler with 20 dB directivity the answer can be anywhere between infinity to 14 dB. (Full cancellation of the two reflection coefficients to the sum of the reflection coefficients) In SWR terms, a 1.22:1 load can measure anywhere between 1.0:1 and 1.5:1. A "perfect" load will measure 1.22:1. Folks, these things aren't laboratory instruments and until Elecraft builds in vector network analyzers with full error correction this is what we get. Wes N7WS On 6/21/2018 11:17 PM, Paul Baldock wrote: > First let me say that other than some issues with the ATU, I am after a week > of use, very happy with the KPA1500. > > So here's the ATU issues: > > I find that the ATU very rarely will learn a setting to get the SWR below > 1.2:1 on any band. I can usually tweak it down to 1.0:1 using the Utility > Program. And yes, before anybody asks, I have ATU STOP TUNE and the ATU > BYPASS set at 1.0:1. > > On 6M into a perfect load (laboratory quality to 8GHz) with the ATU bypassed, > the internal SWR meter reads 1.4:1 I would have expected it to be 1.0:1, but > Elecraft tell me it is normal. So the ATU on 6M will have to tune out what is > left when the 1.4:1 internal mismatch sees your external antenna mismatch. > Maybe this is contributing to your problem. Try adding a quarter wave of coax, > maybe it will achieve a better match. Fortunately my 6M antenna is flat enough > that I can work CW, SSB and FT-8 in BYPASS. > > For your interest, on 10M in to perfect load with ATU bypassed the internal > SWR meter reads 1.2:1. Not 1.0:1. > > Another issue I have with the ATU is that the internal frequency counter has > 8KHz resolution which according to one of the Elecraft techs can lead to a > 16KHz error in measurement. It appears that during "learning" that the ATU is > based on the internal frequency counter measurement, not the frequency you > transceiver sends to the KPA1500.This means that on the bands that have 10KHz > or 20KHz segments, you cannot be sure which segment you are using, and when > you use the tuner it could be in a different segment. Being off by a segment > could be a problem with a high Q antenna. > > Apparently the counter originally had 1KHz resolution but was changed to fix > some other problem. An Elecraft tech told me they currently have no plan to > change it back to 1KHz. I am not suggesting that the
Re: [Elecraft] KPA-1500 ATU not working well
Putting the Elecraft CP1 through the paces with a 2 port VNA can be enlightening. The CP1 seems to be representative of Elecraft directional couplers across the line. There's a picture of the W2 high power HF coupler in the manual, it's just larger cores. Sweeping a 20 dB CP1 across the band with a VNWA with a 60 Ohm load, 1.2:1, results with a relative constant -40 dB reflected gain and a -20 forward gain. A closer match to 50 Ohm fall's apart with a wide -40 db to -70 dB dip at 7 MHz reflected across the band at 50 Ohm. I can agree, 1.2 : 1 is about the limit. John KN5L On 06/22/2018 01:11 PM, Wes Stewart wrote: > That's a return loss of ~20 dB. Now I have > no idea of what the directivity of the coupler is in the KAT500 or KPA1500 > but > considering it has to work from 1.8 to 54 MHz and to keep the numbers easy, > 20 > dB wouldn't be unreasonable. __ 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] KPA-1500 ATU not working well
"If 1.5:1 does this, then that's good enough in my book. Furthermore, a better match might entail higher tuner losses. So why worry about it? My test data for my KPA500 show there is a very significant difference in PA dissipation and also in harmonic output for loads giving indicated 1.4:1 SWR and loads giving 1.0:1 SWR.When I have a more complete data set I'll make it available for peer review. My tentative conclusion is that even a moderate mismatch of KPA500 load is quite detrimental. 73, Andy k3wyc __ 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] KPA-1500 ATU not working well
I have found that if the KPA1500 is feeding a largish SWR (like 1.5:1 as you suggest) then the drive power required to maintain a constant output will vary significantly as you tune across a band. This means you have to keep adjusting the power control within a single band. This appears not to occur if the SWR is 1.1:1 or better. I don't know, but I would guess a solid state untuned amplifier efficiency is better into a 1:1 SWR than a 1:5:1. This could lead to the dreaded more fan noise. By the way by suggesting 1.0:1. I did not mean exactly 1.000:1. I tired to infer 1 digit resolution/accuracy. - Paul KW7Y At 11:11 AM 6/22/2018, Wes Stewart wrote: I do not, and probably never will, have a KPA1500. I do have a KPA500 and KAT500 so I think I can comment. In my opinion, the function of these tuners is to provide a match into which the amp can deliver full power. If 1.5:1 does this, then that's good enough in my book. Furthermore, a better match might entail higher tuner losses. So why worry about it? Another thing; a 1.0:1 SWR infers infinite return loss. To measure infinite return loss, you need a directional coupler with infinite directivity or some mathematical correction derived from very well known calibration standards and no other errors, So maybe you say, 1.0:1 can't be measured (you would be correct), let's shoot for 1.22:1.  That's a return loss of ~20 dB. Now I have no idea of what the directivity of the coupler is in the KAT500 or KPA1500 but considering it has to work from 1.8 to 54 MHz and to keep the numbers easy, 20 dB wouldn't be unreasonable. (Note: I'm only considering the directivity error, there are several others, internal mismatches, frequency tracking, detector non-linearities, etc.) If we measure a load with 20 dB RL using a directional coupler with 20 dB directivity the answer can be anywhere between infinity to 14 dB. (Full cancellation of the two reflection coefficients to the sum of the reflection coefficients) In SWR terms, a 1.22:1 load can measure anywhere between 1.0:1 and 1.5:1. A "perfect" load will measure 1.22:1. Folks, these things aren't laboratory instruments and until Elecraft builds in vector network analyzers with full error correction this is what we get. Wes N7WS On 6/21/2018 11:17 PM, Paul Baldock wrote: > First let me say that other than some issues with the ATU, I am after a week > of use, very happy with the KPA1500. > > So here's the ATU issues: > > I find that the ATU very rarely will learn a setting to get the SWR below > 1.2:1 on any band. I can usually tweak it down to 1.0:1 using the Utility > Program. And yes, before anybody asks, I have ATU STOP TUNE and the ATU > BYPASS set at 1.0:1. > > On 6M into a perfect load (laboratory quality to 8GHz) with the ATU bypassed, > the internal SWR meter reads 1.4:1 I would have expected it to be 1.0:1, but > Elecraft tell me it is normal. So the ATU on 6M will have to tune out what is > left when the 1.4:1 internal mismatch sees your external antenna mismatch. > Maybe this is contributing to your problem. Try adding a quarter wave of coax, > maybe it will achieve a better match. Fortunately my 6M antenna is flat enough > that I can work CW, SSB and FT-8 in BYPASS. > > For your interest, on 10M in to perfect load with ATU bypassed the internal > SWR meter reads 1.2:1. Not 1.0:1. > > Another issue I have with the ATU is that the internal frequency counter has > 8KHz resolution which according to one of the Elecraft techs can lead to a > 16KHz error in measurement. It appears that during "learning" that the ATU is > based on the internal frequency counter measurement, not the frequency you > transceiver sends to the KPA1500.This means that on the bands that have 10KHz > or 20KHz segments, you cannot be sure which segment you are using, and when > you use the tuner it could be in a different segment. Being off by a segment > could be a problem with a high Q antenna. > > Apparently the counter originally had 1KHz resolution but was changed to fix > some other problem. An Elecraft tech told me they currently have no plan to > change it back to 1KHz. I am not suggesting that the tuner should change > segments exactly on their edge. Clearly there has to be some hysteresis to > stop hunting. 25% of a segment width might width be a good number to choose, > but this would require the current frequency counter to have improved resolution. > > > - Paul KW7Y __ 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
Re: [Elecraft] KPA-1500 ATU not working well
I do not, and probably never will, have a KPA1500. I do have a KPA500 and KAT500 so I think I can comment. In my opinion, the function of these tuners is to provide a match into which the amp can deliver full power. If 1.5:1 does this, then that's good enough in my book. Furthermore, a better match might entail higher tuner losses. So why worry about it? Another thing; a 1.0:1 SWR infers infinite return loss. To measure infinite return loss, you need a directional coupler with infinite directivity or some mathematical correction derived from very well known calibration standards and no other errors, So maybe you say, 1.0:1 can't be measured (you would be correct), let's shoot for 1.22:1. That's a return loss of ~20 dB. Now I have no idea of what the directivity of the coupler is in the KAT500 or KPA1500 but considering it has to work from 1.8 to 54 MHz and to keep the numbers easy, 20 dB wouldn't be unreasonable. (Note: I'm only considering the directivity error, there are several others, internal mismatches, frequency tracking, detector non-linearities, etc.) If we measure a load with 20 dB RL using a directional coupler with 20 dB directivity the answer can be anywhere between infinity to 14 dB. (Full cancellation of the two reflection coefficients to the sum of the reflection coefficients) In SWR terms, a 1.22:1 load can measure anywhere between 1.0:1 and 1.5:1. A "perfect" load will measure 1.22:1. Folks, these things aren't laboratory instruments and until Elecraft builds in vector network analyzers with full error correction this is what we get. Wes N7WS On 6/21/2018 11:17 PM, Paul Baldock wrote: First let me say that other than some issues with the ATU, I am after a week of use, very happy with the KPA1500. So here's the ATU issues: I find that the ATU very rarely will learn a setting to get the SWR below 1.2:1 on any band. I can usually tweak it down to 1.0:1 using the Utility Program. And yes, before anybody asks, I have ATU STOP TUNE and the ATU BYPASS set at 1.0:1. On 6M into a perfect load (laboratory quality to 8GHz) with the ATU bypassed, the internal SWR meter reads 1.4:1 I would have expected it to be 1.0:1, but Elecraft tell me it is normal. So the ATU on 6M will have to tune out what is left when the 1.4:1 internal mismatch sees your external antenna mismatch. Maybe this is contributing to your problem. Try adding a quarter wave of coax, maybe it will achieve a better match. Fortunately my 6M antenna is flat enough that I can work CW, SSB and FT-8 in BYPASS. For your interest, on 10M in to perfect load with ATU bypassed the internal SWR meter reads 1.2:1. Not 1.0:1. Another issue I have with the ATU is that the internal frequency counter has 8KHz resolution which according to one of the Elecraft techs can lead to a 16KHz error in measurement. It appears that during "learning" that the ATU is based on the internal frequency counter measurement, not the frequency you transceiver sends to the KPA1500.This means that on the bands that have 10KHz or 20KHz segments, you cannot be sure which segment you are using, and when you use the tuner it could be in a different segment. Being off by a segment could be a problem with a high Q antenna. Apparently the counter originally had 1KHz resolution but was changed to fix some other problem. An Elecraft tech told me they currently have no plan to change it back to 1KHz. I am not suggesting that the tuner should change segments exactly on their edge. Clearly there has to be some hysteresis to stop hunting. 25% of a segment width might width be a good number to choose, but this would require the current frequency counter to have improved resolution. - Paul KW7Y __ 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] KPA-1500 ATU not working well
At 09:28 AM 6/22/2018, K9MA wrote: That would explain why I sometimes hear the relays click again when I transmit (I think). Seems that could be fixed by simply requiring that the difference be more than, say, 20 kHz before the counter takes priority. Scott K9MA You are not imagining it. I have EMailed supp...@elecraft.com with my concerns. Maybe if others do also, they will consider a change. - Paul On 6/22/2018 11:00, Paul Baldock wrote: True, it then double checks with the internal frequency counter once rf is applied, and may choose a different segment if the internal counter disagrees. - Paul At 08:48 AM 6/22/2018, K9MA wrote: But wait! I know I hear the ATU relays switch when I stop tuning the K3, before transmitting. Scott K9MA On 6/22/2018 10:01, Paul Baldock wrote: They want to be certain that the amp is on the correct band, should the data from the radio be incorrect. - PaulàKW7Y I wonder why this is so. Scott K9MA -- Scott Ellington à --- via iPad > On Jun 22, 2018, at 1:17 AM, Paul Baldock wrote: > > frequency counter measurement, not the frequency you transceiver sends to the KPA1500. -- Scott K9MA 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] KPA-1500 ATU not working well
That would explain why I sometimes hear the relays click again when I transmit (I think). Seems that could be fixed by simply requiring that the difference be more than, say, 20 kHz before the counter takes priority. Scott K9MA On 6/22/2018 11:00, Paul Baldock wrote: True, it then double checks with the internal frequency counter once rf is applied, and may choose a different segment if the internal counter disagrees. - Paul At 08:48 AM 6/22/2018, K9MA wrote: But wait! I know I hear the ATU relays switch when I stop tuning the K3, before transmitting. Scott K9MA On 6/22/2018 10:01, Paul Baldock wrote: They want to be certain that the amp is on the correct band, should the data from the radio be incorrect. - Paul KW7Y I wonder why this is so. Scott K9MA -- Scott Ellington  --- via iPad > On Jun 22, 2018, at 1:17 AM, Paul Baldock wrote: > > frequency counter measurement, not the frequency you transceiver sends to the KPA1500. -- Scott K9MA 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] KPA-1500 ATU not working well
True, it then double checks with the internal frequency counter once rf is applied, and may choose a different segment if the internal counter disagrees. - Paul At 08:48 AM 6/22/2018, K9MA wrote: But wait! I know I hear the ATU relays switch when I stop tuning the K3, before transmitting. Scott K9MA On 6/22/2018 10:01, Paul Baldock wrote: They want to be certain that the amp is on the correct band, should the data from the radio be incorrect. - Paul KW7Y I wonder why this is so. Scott K9MA -- Scott Ellington  --- via iPad > On Jun 22, 2018, at 1:17 AM, Paul Baldock wrote: > > frequency counter measurement, not the frequency you transceiver sends to the KPA1500. -- 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] KPA-1500 ATU not working well
But wait! I know I hear the ATU relays switch when I stop tuning the K3, before transmitting. Scott K9MA On 6/22/2018 10:01, Paul Baldock wrote: They want to be certain that the amp is on the correct band, should the data from the radio be incorrect. - Paul KW7Y I wonder why this is so. Scott K9MA -- Scott Ellington --- via iPad > On Jun 22, 2018, at 1:17 AM, Paul Baldock wrote: > > frequency counter measurement, not the frequency you transceiver sends to the KPA1500. -- 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] KPA-1500 ATU not working well
"It might be but the amp is designed to work with radios other than K3s." The KPA1500 and KPA500 are both capable of receiving frequency from transceivers other than the K3S, so is the KAT500. I don't see how not using a K3S puts any limitation on my proposal. 73, Andy k3wyc __ 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] KPA-1500 ATU not working well
They want to be certain that the amp is on the correct band, should the data from the radio be incorrect. - Paul KW7Y I wonder why this is so. Scott K9MA -- Scott Ellington --- via iPad > On Jun 22, 2018, at 1:17 AM, Paul Baldock wrote: > > frequency counter measurement, not the frequency you transceiver sends to the KPA1500. __ 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] KPA-1500 ATU not working well
Andy - Sounds like a great idea. - Paul 6/22/2018, ANDY DURBIN wrote: "Clearly there has to be some hysteresis to stop hunting. 25% of a segment width might width be a good number to choose, but this would require the current frequency counter to have improved resolution." Why wouldn't it be preferable to use the transceiver's exact TX frequency, if available, for learning and selection ? Yes, I understand that Elecraft likes to give the detected RF frequency the highest priority. However, the logic required to allow use of transceiver frequency if difference from RF defected frequency did not exceed a defined limit would not seem to be too complex. 73, Andy k3wyc __ 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] KPA-1500 ATU not working well
I wonder why this is so. Scott K9MA -- Scott Ellington --- via iPad > On Jun 22, 2018, at 1:17 AM, Paul Baldock wrote: > > frequency counter measurement, not the frequency you transceiver sends to the > KPA1500. __ 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] KPA-1500 ATU not working well
It might be but the amp is designed to work with radios other than K3s. On 6/22/2018 5:01 AM, ANDY DURBIN wrote: Why wouldn't it be preferable to use the transceiver's exact TX frequency, if available, __ 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] KPA-1500 ATU not working well
"Clearly there has to be some hysteresis to stop hunting. 25% of a segment width might width be a good number to choose, but this would require the current frequency counter to have improved resolution." Why wouldn't it be preferable to use the transceiver's exact TX frequency, if available, for learning and selection ? Yes, I understand that Elecraft likes to give the detected RF frequency the highest priority. However, the logic required to allow use of transceiver frequency if difference from RF defected frequency did not exceed a defined limit would not seem to be too complex. 73, Andy k3wyc __ 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] KPA-1500 ATU not working well
First let me say that other than some issues with the ATU, I am after a week of use, very happy with the KPA1500. So here's the ATU issues: I find that the ATU very rarely will learn a setting to get the SWR below 1.2:1 on any band. I can usually tweak it down to 1.0:1 using the Utility Program. And yes, before anybody asks, I have ATU STOP TUNE and the ATU BYPASS set at 1.0:1. On 6M into a perfect load (laboratory quality to 8GHz) with the ATU bypassed, the internal SWR meter reads 1.4:1 I would have expected it to be 1.0:1, but Elecraft tell me it is normal. So the ATU on 6M will have to tune out what is left when the 1.4:1 internal mismatch sees your external antenna mismatch. Maybe this is contributing to your problem. Try adding a quarter wave of coax, maybe it will achieve a better match. Fortunately my 6M antenna is flat enough that I can work CW, SSB and FT-8 in BYPASS. For your interest, on 10M in to perfect load with ATU bypassed the internal SWR meter reads 1.2:1. Not 1.0:1. Another issue I have with the ATU is that the internal frequency counter has 8KHz resolution which according to one of the Elecraft techs can lead to a 16KHz error in measurement. It appears that during "learning" that the ATU is based on the internal frequency counter measurement, not the frequency you transceiver sends to the KPA1500.This means that on the bands that have 10KHz or 20KHz segments, you cannot be sure which segment you are using, and when you use the tuner it could be in a different segment. Being off by a segment could be a problem with a high Q antenna. Apparently the counter originally had 1KHz resolution but was changed to fix some other problem. An Elecraft tech told me they currently have no plan to change it back to 1KHz. I am not suggesting that the tuner should change segments exactly on their edge. Clearly there has to be some hysteresis to stop hunting. 25% of a segment width might width be a good number to choose, but this would require the current frequency counter to have improved resolution. - Paul KW7Y At 08:53 PM 6/21/2018, K9MA wrote: Dick, Have you tried manually adjusting the ATU? I haven't used mine on 6 meters, but on other bands, no matter what I do, it sometimes doesn't get a very good match automatically, and I can do better manually. On the other hand, it may be that the L and C step sizes are just too big to get a good match on 6. Or there could actually be something wrong. If you have a good 50 MHz dummy load, try that with the ATU in. 73, Scott K9MA On 6/21/2018 22:40, Dick via Elecraft wrote: > I'm wondering if anyone else is having problems with their KPA-1500 ATU on 6-meters? My antenna is cut for 50.100 and has a 2.2:1 SWR at the 50.313 FT-8 frequency. The very best the ATU will do is to lower the SWR from 2.2:1 down to 2.0:1 which is almost no improvement. The 2.0 to 1 is with exciter power, when I switch the KPA-1500 to operate and transmit at 1,200 watts the SWR increases to aprx. 2.2 to 1 and the KPA-1500 will fault and trip off occassionally. Hoping there's a fix for this. > > I'm using the latest KPA-1500 firmware. > > Thanks, > Dick- K9OM > > > > __ > 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 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] KPA-1500 ATU not working well
Hi, I am currently out of the office until July 1, 2018. If you purchased a license, and have not received it, it is almost 100% sure to be in your spam, junk or other such folder. In Gmail it will be in the web version of gmail. Please check for it there. All my websites have a section called Documentation. In there you will find video tutorials and lot's of help. 73 Tom --- 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: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] KPA-1500 ATU not working well
Dick, Have you tried manually adjusting the ATU? I haven't used mine on 6 meters, but on other bands, no matter what I do, it sometimes doesn't get a very good match automatically, and I can do better manually. On the other hand, it may be that the L and C step sizes are just too big to get a good match on 6. Or there could actually be something wrong. If you have a good 50 MHz dummy load, try that with the ATU in. 73, Scott K9MA On 6/21/2018 22:40, Dick via Elecraft wrote: I'm wondering if anyone else is having problems with their KPA-1500 ATU on 6-meters? My antenna is cut for 50.100 and has a 2.2:1 SWR at the 50.313 FT-8 frequency. The very best the ATU will do is to lower the SWR from 2.2:1 down to 2.0:1 which is almost no improvement. The 2.0 to 1 is with exciter power, when I switch the KPA-1500 to operate and transmit at 1,200 watts the SWR increases to aprx. 2.2 to 1 and the KPA-1500 will fault and trip off occassionally. Hoping there's a fix for this. I'm using the latest KPA-1500 firmware. Thanks, Dick- K9OM __ 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
[Elecraft] KPA-1500 ATU not working well
I'm wondering if anyone else is having problems with their KPA-1500 ATU on 6-meters? My antenna is cut for 50.100 and has a 2.2:1 SWR at the 50.313 FT-8 frequency. The very best the ATU will do is to lower the SWR from 2.2:1 down to 2.0:1 which is almost no improvement. The 2.0 to 1 is with exciter power, when I switch the KPA-1500 to operate and transmit at 1,200 watts the SWR increases to aprx. 2.2 to 1 and the KPA-1500 will fault and trip off occassionally. Hoping there's a fix for this. I'm using the latest KPA-1500 firmware. Thanks, Dick- K9OM __ 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
