Experience with KXPA100
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Experience with KXPA100
 
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Hello,
My KXPA100 ser.nr. 00822 has now been on the air for several months and produced several hundred QSO's. The performance however, is mixed. The output power varies from one band to another with the output set on the KX3 to 110 Watts and using the KXPA100 utility for meetering and a dummy load. The antenna tuner is in manual and SWR indicated to be between 1:1 and 1:1.1 from 160 M to 10 M. The best band is 20 M, where the KXPA100 will produce 112 Watts out with 5.5 Watts driving power and an indicated power dissipation of 62 Watts. The worst band is 40 M where the KXPA 100 only will produce 83 watts out with 2.8 Watts drive and an indicated power dissipation of 92 Watts. On 80 M the KXPA100 utility shows a power dissipation of 118 Watts and an output power of 89 Watts. Except on 20 M no band produce more than 90 to 95 Watts output. I am surprised by the big variation in efficiency. Almost twice the loss on 80 M compared to 20 M. Besides there seems to be plenty of drive power, so why less than full power on most bands? Has anyone else observed similar variations? 73 OZ7BQ, Hans Jørgen (Joe) ______________________________________________________________ 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 Hans
My kapa100 kit serial #360 is doing the same as yours I was under the impression that there was a refinement to the firmware that was going to fix this issue. Regards Art ka9zap /* On 6/24/2014 2:11 PM, Hans J Rasmusen OZ7BQ wrote: > Hello, > > My KXPA100 ser.nr. 00822 has now been on the air for several months and produced several hundred QSO's. The performance however, is mixed. > The output power varies from one band to another with the output set on the KX3 to 110 Watts and using the KXPA100 utility for meetering and a dummy load. The antenna tuner is in manual and SWR indicated to be between 1:1 and 1:1.1 from 160 M to 10 M. > > The best band is 20 M, where the KXPA100 will produce 112 Watts out with 5.5 Watts driving power and an indicated power dissipation of 62 Watts. > The worst band is 40 M where the KXPA 100 only will produce 83 watts out with 2.8 Watts drive and an indicated power dissipation of 92 Watts. > On 80 M the KXPA100 utility shows a power dissipation of 118 Watts and an output power of 89 Watts. > Except on 20 M no band produce more than 90 to 95 Watts output. > > > I am surprised by the big variation in efficiency. Almost twice the loss on 80 M compared to 20 M. Besides there seems to be plenty of drive power, so why less than full power on most bands? > > Has anyone else observed similar variations? > > 73 OZ7BQ, Hans Jørgen (Joe) > ______________________________________________________________ > 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 Hans J Rasmusen OZ7BQ
Hi Hans,
The first thing to check for is insufficient power-supply voltage as measured by KXPA Utility on key-down at full power. This is the usual reason for lower power output. If it's too low, you might try any of the following: shorten the supply cable, double up the cable (there are two APP jacks), adjust the supply voltage slightly higher (it's rated at up to 15 V), or make sure you don't have high-drop fuses or other devices in-line with the cable. Power output of the KXPA100 is specified as: Max. 100 W @ 13.8 V, 1.8 to 29.7 MHz (80 watts 50-54 MHz) PEP, CW/SSB/DATA, +/- 1 dB And as noted in the specs, maximum power output, as well as the drive power to reach a given power output, both vary per-band. Your results do fall into that +/- 1 dB spec range. However, we actually test the amps at 100 W in the factory and it is very rare that they don't make 100+ W on all HF bands. (We could have specified it as -0.5/+1.0 dB based on our cumulative test results.) We tested competing amplifiers that use the same PA devices, and they too have a wide range of drive required and max output, varying per-band, and sometimes a dB below 100 W. This is typical of available 12-V-class MOSFETs. I do have a task on my list to increase the maximum allowed drive from the KX3 when higher power levels are used. We've been very conservative in this regard, so far, since KXPA100s are often used with marginal power sources and antennas in the field, or mobile. We don't want to over-drive, which could result in splatter or distortion of the KX3's virtually click-free CW key shaping. If you need further assistance with this, please contact customer support. 73, Wayne N6KR On Jun 24, 2014, at 12:11 PM, Hans J Rasmusen OZ7BQ <[hidden email]> wrote: > Hello, > > My KXPA100 ser.nr. 00822 has now been on the air for several months ….power varies from one band to another…. ______________________________________________________________ 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 Hans J Rasmusen OZ7BQ
Hans,
I did the same tests and indeed the lowest efficiency is on 10v and 160m bands with output power of 94 W and dissipated power of 135 W. I did not measure 6m. But compromise like that might have been expected in the unit covering such a great span of frequencies. Regarding the low output power, it much depends on the voltage of the power supply and voltage drop on the feeding wires. With factory supplied feeding wires and voltage of 14.8 V set on the power supply I can get between 94 and 110 W out on all the bands. The voltage drop at this power is about 1.2 V according to KX3 meter. Therefore at 13.6 V by the meter KXPA100 indeed delivers close to 100 W. I get only around 84 W on 10m band when the amp is fed from 13.2V LiFePO4 battery. The voltage meter of KX3 shows then 11.1 V at that power. IMHO KXPA100 is pretty sensitive to voltage of the power supply. 73, Igor UA9CDC ----- Original Message ----- From: "Hans J Rasmusen OZ7BQ" <[hidden email]> To: <[hidden email]> Sent: Wednesday, June 25, 2014 1:11 AM Subject: [Elecraft] Experience with KXPA100 Hello, My KXPA100 ser.nr. 00822 has now been on the air for several months and produced several hundred QSO's. The performance however, is mixed. The output power varies from one band to another with the output set on the KX3 to 110 Watts and using the KXPA100 utility for meetering and a dummy load. The antenna tuner is in manual and SWR indicated to be between 1:1 and 1:1.1 from 160 M to 10 M. The best band is 20 M, where the KXPA100 will produce 112 Watts out with 5.5 Watts driving power and an indicated power dissipation of 62 Watts. The worst band is 40 M where the KXPA 100 only will produce 83 watts out with 2.8 Watts drive and an indicated power dissipation of 92 Watts. On 80 M the KXPA100 utility shows a power dissipation of 118 Watts and an output power of 89 Watts. Except on 20 M no band produce more than 90 to 95 Watts output. I am surprised by the big variation in efficiency. Almost twice the loss on 80 M compared to 20 M. Besides there seems to be plenty of drive power, so why less than full power on most bands? Has anyone else observed similar variations? 73 OZ7BQ, Hans Jørgen (Joe) ______________________________________________________________ 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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Er... um... is such a large voltage drop typical? We don't see that
happening on Brand X amps using good power supplies. I understand the voltage drop when going from, say, 10 to 100 watts should be minimal, like no more than .2 volts. I have also seen this sort of power output weakness in some transceivers which are rather picky about voltage sag when running full tilt. I would check the power supply and try one that does not sag more than .1 or .2 volts on full power. I suspect the amp is good, the power supply not. Just My take. -------------------- K8JHR -------------- On 6/24/2014 4:46 PM, Igor Sokolov wrote: it much depends on the voltage of the > power supply and voltage drop on the feeding wires. The voltage drop at this power is about 1.2 V according to KX3 meter. The voltage meter of KX3 shows then 11.1 V at that power. > IMHO KXPA100 is pretty sensitive to voltage of the power supply. ================================================ / ______________________________________________________________ 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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Really depends on the gauge and length of wire you're using. Find your wire
data, for instance at http://www.powerstream.com/Wire_Size.htm. You'll be shocked at how much voltage you can drop at 100 watts using a few feet of what you thought was heavy gauge wire. Example: 12 gauge wire is 1.6 milli-ohm per foot. Two conductors -> 3.2 milli ohms per foot. Six feet of wire = 19 milli ohms. 19 milli ohms x 20 amps = 0.4 volts. So yeah, it's easy to lose more then 0.2 volts. 73, Carl WS7L On Tue, Jun 24, 2014 at 5:37 PM, K8JHR <[hidden email]> wrote: > Er... um... is such a large voltage drop typical? We don't see that > happening on Brand X amps using good power supplies. I understand the > voltage drop when going from, say, 10 to 100 watts should be minimal, like > no more than .2 volts. ______________________________________________________________ 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 JHRichards
It was worth mentioning that my KX3 is supplied from the second pair of APP
connectors of KXPA100. Therefore KX3 shows the total voltage drop on all the wires including relatively thin wires going from KXPA100 to KX3. These wires add about 0.6V drop to the picture. The power supply though is pretty good. It is ALINCO 330 capable of 30 amps. I just wanted to stress that output power of KXPA100 is pretty dependant on PS voltage and voltage drop in the wires. 73, Igor UA9CDC ----- Original Message ----- From: "K8JHR" <[hidden email]> To: <[hidden email]> Sent: Wednesday, June 25, 2014 6:37 AM Subject: Re: [Elecraft] Experience with KXPA100 > Er... um... is such a large voltage drop typical? We don't see that > happening on Brand X amps using good power supplies. I understand the > voltage drop when going from, say, 10 to 100 watts should be minimal, like > no more than .2 volts. I have also seen this sort of power output > weakness in some transceivers which are rather picky about voltage sag > when running full tilt. > > I would check the power supply and try one that does not sag more than .1 > or .2 volts on full power. I suspect the amp is good, the power supply > not. > > Just My take. > -------------------- K8JHR -------------- > > On 6/24/2014 4:46 PM, Igor Sokolov wrote: > > it much depends on the voltage of the >> power supply and voltage drop on the feeding wires. > > The voltage drop at this power is about 1.2 V according > to KX3 meter. > > The voltage meter of KX3 shows then 11.1 V at that power. >> IMHO KXPA100 is pretty sensitive to voltage of the power supply. > > > ================================================ > > > > > > / > ______________________________________________________________ > 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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I also use the same Alinco 330 PSU. It is a good PSU with stable output and no noticeable RFI.
73 Johnny VR2XMC ________________________________ 寄件人︰ Igor Sokolov <[hidden email]> 收件人︰ K8JHR <[hidden email]>; [hidden email] 傳送日期︰ 2014年06月26日 (週四) 10:27 AM 主題︰ Re: [Elecraft] Experience with KXPA100 It was worth mentioning that my KX3 is supplied from the second pair of APP connectors of KXPA100. Therefore KX3 shows the total voltage drop on all the wires including relatively thin wires going from KXPA100 to KX3. These wires add about 0.6V drop to the picture. The power supply though is pretty good. It is ALINCO 330 capable of 30 amps. I just wanted to stress that output power of KXPA100 is pretty dependant on PS voltage and voltage drop in the wires. 73, Igor UA9CDC ----- Original Message ----- From: "K8JHR" <[hidden email]> To: <[hidden email]> Sent: Wednesday, June 25, 2014 6:37 AM Subject: Re: [Elecraft] Experience with KXPA100 > Er... um... is such a large voltage drop typical? We don't see that > happening on Brand X amps using good power supplies. I understand the > voltage drop when going from, say, 10 to 100 watts should be minimal, like > no more than .2 volts. I have also seen this sort of power output > weakness in some transceivers which are rather picky about voltage sag > when running full tilt. > > I would check the power supply and try one that does not sag more than .1 > or .2 volts on full power. I suspect the amp is good, the power supply > not. > > Just My take. > -------------------- K8JHR -------------- > > On 6/24/2014 4:46 PM, Igor Sokolov wrote: > > it much depends on the voltage of the >> power supply and voltage drop on the feeding wires. > > The voltage drop at this power is about 1.2 V according > to KX3 meter. > > The voltage meter of KX3 shows then 11.1 V at that power. >> IMHO KXPA100 is pretty sensitive to voltage of the power supply. > > > ================================================ > > > > > > / > ______________________________________________________________ > 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] ______________________________________________________________ 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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