Re: [Elecraft] [QRO] KPA500 variation of PA current band-by-band
Guys,
On the other hand, there nothing wrong with trying to characterize the
beastie you have as best you can. If for no other reason to see if
something changes with time and how much.
Also, how does my kit comparing to other kits which presumable have
similar but not identical characteristics? Note with the exception of
the dummy load impedance, all instrumentation used is within the
KPA-500. For what it is worth, my measurements were made with a WATERS
1.5 kW dummy load which the KPA-500 thinks is 1.1 to 1 across the 9 HF
bands. Even if it were 1.5 :1 you're talking about introducing 20 watts
of reflected power. I assume the KPA-500 is reading forward power and
not forward-reflected. Thus these kinds of error would make the output
power read higher than reality, not lower.
Also look it at a learning experience. This is my first solid state
amp. I know what to expect from tube amps but not solid state ones.
How does a solid state amp behave in the efficiency department vs
frequency? When one sees it takes 16 amps on one band to produce 500
watts and 11 on another, there is plenty reason to raise questions and
want to understand why.
One thing uncovered already is that current is measured by a Hall effect
device instead of the time honored low value series resistor/voltmeter
combo. What is it's accuracy? Could that device's accuracy explain a
significant amount some of the variations seen.
To me it's about understaning my beastie.
Certainly people should not be castigated for asking questions. We are
not all EE's with 50 years experience and a shop full of precision
measuring equipment.
73 de Brian/K3KO
On 2/8/2012 03:19, Don Wilhelm wrote:
Guy and all,
You are so correct. This is ham radio, and precision instrumentation
for power output levels is not the norm - a 20% error potential should
always be considered.
Yes, I personally have power instrumentation that is calibrated to the 5
% level up to 30 MHz. That level of precision has come at a goodly cost
and effort.
In general, amateur quality power measurement gear should be given a +/-
20% range of error. There are variations due to frequency, variations
due to changes in the dummy load actual impedance, and if one is using
an antenna, any common mode RF current can substantially influence the
readings on the meters.
In other words, what you see on your power meter may or may not reflect
reality. If there is any doubt about your results, tell me what your
results are when driving a known good 50 ohm non-reactive dummy load
(measure it with your antenna analyzer), and if a problem is indicated
with that load, then you can conclude that you have a transceiver
problem. If it is OK into that dummy load, but gives problems driving
your antenna, then you will have to solve the problem in your antenna field.
These are generalized statements and not directed at any particular
installation. If you and your indications are suspect, then investigate
your particular situation carefully (it is possible that we can help).
73,
Don W3FPR
On 2/7/2012 9:40 PM, Guy Olinger K2AV wrote:
Hmmm,
Given that ham-affordable components are full of minor and harmless
frequency dependent characteristics, INCLUDING the antennas and dummy loads
used, is there really any good reason to EXPECT 1.8-30 power output
uniformity beyond what is commonly measured? Quite contrary to amps which
were designed, built and certified to a broadband tight uniformity (and
appropriately priced), if one WANTS exactly 500.0 watts from a KPA500 for
some purpose, and you actually trust your output measuring instrument to
deliver an accurate measurement to four figures, one just adjusts the
drive, does one not?
This is ham gear, not lab instruments, but I would be intrigued to hear
what purpose this debated level of accuracy serves, other than light
entertainment. I have sometimes heard some very interesting stuff coming
from the other side of what I thought was the left field foul line. One
never knows.
???
73, Guy.
On Tue, Feb 7, 2012 at 3:23 PM,n...@n5ge.com wrote:
Is your dummy load absolutely a flat 1.0:1 from 1.0MHz to 30MHz?
73,
Tom
Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member
Only the white eyes would believe they could cut the top
off a blanket, sew it to the bottom and have a longer
blanket.
-- American Indian comment about Daylight Saving Time --
On Tue, 07 Feb 2012 13:35:47 +, Brian Alsopals...@nc.rr.com wrote:
Guys,
I'm also curious about this-- especially what's going on on 15M.
My values at 500 W out into a dummy load are:
(amp), [volts], {efficiency}
1.8MHz DC (11.5) [63.1] {70}
3.5MHz (11.2) [63.5] {71}
7MHz(12.2) [62.5] {67}
10.1MHz (not measured)
14MHz (13.4)[61.8] {60}
18.1MHz (12.9)[62.8] (63}
21MHz (15.8)[61.2] {52}
24.9MHz (14.6) [60.1] {56}
29.7MHz (14.7)[60.4]
Re: [Elecraft] [QRO] KPA500 variation of PA current band-by-band
Guys,
I'm also curious about this-- especially what's going on on 15M.
My values at 500 W out into a dummy load are:
(amp), [volts], {efficiency}
1.8MHz DC (11.5) [63.1] {70}
3.5MHz (11.2) [63.5] {71}
7MHz(12.2) [62.5] {67}
10.1MHz (not measured)
14MHz (13.4)[61.8] {60}
18.1MHz (12.9)[62.8] (63}
21MHz (15.8)[61.2] {52}
24.9MHz (14.6) [60.1] {56}
29.7MHz (14.7)[60.4] {56}
These are in reasonable agreement with David's except for perhaps 10M.
The problem with these measurements are the wattmeter accuracy (10%?)
and the current measurement inaccuracy. Default wattmeter calibration
factors were used above. Elecraft is using a Hall effect device to
measure PA current. It would be nice to know just what accuracy to
expect from it.
The efficiencies appear to be in the right ballpark. They tend to fall
on a straight line log plot vs frequency, decreasing at higher freq's.
If nothing else, the above numbers serve as a benchmark for future
comparisons down the road for my amp.
Note: The current measurement can be significantly affected by RF on the
outside shield of the coax. Until a choke was employed on the feedline,
the 24.9 MHz current with a real antenna measured 3 amps too low. With
the choke it agreed with the above dummy load value. I suspect lots of
KPA-500 users do have this condition-- given the types of
antennas/tuners et al described by uses on this reflector.
73 de Brian/K3KO
On 2/4/2012 20:27, david park wrote:
I have recently assembled KPA500 serial number 641. When testing into a
dummy load I find that I get a large variation in the DC power input when
driving for 500W CW when I go from band to band. My worst band is 21MHz,
where I get the highest current (lowest efficiency). The drive was adjusted
to give 500W as indicated by the LCD display. Here are my results:-
1.8MHz DC current 10.0Afan hardly ever comes on
3.5MHz DC current 10.0A fan hardly ever comes on
7MHz 12.0A
10.1MHz12.4A
14MHz 14.3A
18.1MHz13.8A
21MHz 16.4A temperature rises rapidly and fan
soon gets to full speed
24.9MHz13.5A
29.7MHz12.3A
I have no results for 50MHz band as I have no transceiver covering that band.
The readings drift as the heatsink (and the dummy load) warm up, and so I
took readings quickly and allowed time for the heatsink to cool down between
each band. I find that the KPA500 current sensor tends to give low readings.
I would be interested in knowing how other amplifiers perform.
David Park G3PSV
-
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Re: [Elecraft] [QRO] KPA500 variation of PA current band-by-band
When the KPA100 (the K2's 100w amplifier stage) came out, some of us noted
similar issues.
The gain available from a transistor varies in the opposite direction to
frequency, and
the circuits include feedback mechanisms to try to balance it. The
characteristics of real
components have some effect on the behavior of the feedback network; in the
case of the
KPA100, some resistors had more inductance than expected, which resulted in a
severe drop
in gain on some bands.
I guess what I'm saying is that gain variations are expected, and unless the
efficiency is
bad enough to endanger the devices, I wouldn't worry about it.
On 2/7/2012 5:35 AM, Brian Alsop wrote:
Guys,
I'm also curious about this-- especially what's going on on 15M.
My values at 500 W out into a dummy load are:
(amp), [volts], {efficiency}
1.8MHz DC (11.5) [63.1] {70}
3.5MHz (11.2) [63.5] {71}
7MHz(12.2) [62.5] {67}
10.1MHz (not measured)
14MHz (13.4)[61.8] {60}
18.1MHz (12.9)[62.8] (63}
21MHz (15.8)[61.2] {52}
24.9MHz (14.6) [60.1] {56}
29.7MHz (14.7)[60.4] {56}
These are in reasonable agreement with David's except for perhaps 10M.
The problem with these measurements are the wattmeter accuracy (10%?)
and the current measurement inaccuracy. Default wattmeter calibration
factors were used above. Elecraft is using a Hall effect device to
measure PA current. It would be nice to know just what accuracy to
expect from it.
The efficiencies appear to be in the right ballpark. They tend to fall
on a straight line log plot vs frequency, decreasing at higher freq's.
If nothing else, the above numbers serve as a benchmark for future
comparisons down the road for my amp.
Note: The current measurement can be significantly affected by RF on the
outside shield of the coax. Until a choke was employed on the feedline,
the 24.9 MHz current with a real antenna measured 3 amps too low. With
the choke it agreed with the above dummy load value. I suspect lots of
KPA-500 users do have this condition-- given the types of
antennas/tuners et al described by uses on this reflector.
73 de Brian/K3KO
On 2/4/2012 20:27, david park wrote:
I have recently assembled KPA500 serial number 641. When testing into a
dummy load I find that I get a large variation in the DC power input when
driving for 500W CW when I go from band to band. My worst band is 21MHz,
where I get the highest current (lowest efficiency). The drive was adjusted
to give 500W as indicated by the LCD display. Here are my results:-
1.8MHz DC current 10.0Afan hardly ever comes on
3.5MHz DC current 10.0A fan hardly ever comes on
7MHz 12.0A
10.1MHz12.4A
14MHz 14.3A
18.1MHz13.8A
21MHz 16.4A temperature rises rapidly and fan
soon gets to full speed
24.9MHz13.5A
29.7MHz12.3A
I have no results for 50MHz band as I have no transceiver covering that band.
The readings drift as the heatsink (and the dummy load) warm up, and so I
took readings quickly and allowed time for the heatsink to cool down between
each band. I find that the KPA500 current sensor tends to give low readings.
I would be interested in knowing how other amplifiers perform.
David Park G3PSV
-
No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1424 / Virus Database: 2112/4794 - Release Date: 02/07/12
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Re: [Elecraft] [QRO] KPA500 variation of PA current band-by-band
Is your dummy load absolutely a flat 1.0:1 from 1.0MHz to 30MHz?
73,
Tom
Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member
Only the white eyes would believe they could cut the top
off a blanket, sew it to the bottom and have a longer
blanket.
-- American Indian comment about Daylight Saving Time --
On Tue, 07 Feb 2012 13:35:47 +, Brian Alsop als...@nc.rr.com wrote:
Guys,
I'm also curious about this-- especially what's going on on 15M.
My values at 500 W out into a dummy load are:
(amp), [volts], {efficiency}
1.8MHz DC (11.5) [63.1] {70}
3.5MHz (11.2) [63.5] {71}
7MHz(12.2) [62.5] {67}
10.1MHz (not measured)
14MHz (13.4)[61.8] {60}
18.1MHz (12.9)[62.8] (63}
21MHz (15.8)[61.2] {52}
24.9MHz (14.6) [60.1] {56}
29.7MHz (14.7)[60.4] {56}
These are in reasonable agreement with David's except for perhaps 10M.
The problem with these measurements are the wattmeter accuracy (10%?)
and the current measurement inaccuracy. Default wattmeter calibration
factors were used above. Elecraft is using a Hall effect device to
measure PA current. It would be nice to know just what accuracy to
expect from it.
The efficiencies appear to be in the right ballpark. They tend to fall
on a straight line log plot vs frequency, decreasing at higher freq's.
If nothing else, the above numbers serve as a benchmark for future
comparisons down the road for my amp.
Note: The current measurement can be significantly affected by RF on the
outside shield of the coax. Until a choke was employed on the feedline,
the 24.9 MHz current with a real antenna measured 3 amps too low. With
the choke it agreed with the above dummy load value. I suspect lots of
KPA-500 users do have this condition-- given the types of
antennas/tuners et al described by uses on this reflector.
73 de Brian/K3KO
On 2/4/2012 20:27, david park wrote:
I have recently assembled KPA500 serial number 641. When testing into a
dummy load I find that I get a large variation in the DC power input when
driving for 500W CW when I go from band to band. My worst band is 21MHz,
where I get the highest current (lowest efficiency). The drive was adjusted
to give 500W as indicated by the LCD display. Here are my results:-
1.8MHz DC current 10.0Afan hardly ever comes on
3.5MHz DC current 10.0A fan hardly ever comes on
7MHz 12.0A
10.1MHz12.4A
14MHz 14.3A
18.1MHz13.8A
21MHz 16.4A temperature rises rapidly and fan
soon gets to full speed
24.9MHz13.5A
29.7MHz12.3A
I have no results for 50MHz band as I have no transceiver covering that band.
The readings drift as the heatsink (and the dummy load) warm up, and so I
took readings quickly and allowed time for the heatsink to cool down between
each band. I find that the KPA500 current sensor tends to give low readings.
I would be interested in knowing how other amplifiers perform.
David Park G3PSV
-
No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1424 / Virus Database: 2112/4794 - Release Date: 02/07/12
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Re: [Elecraft] [QRO] KPA500 variation of PA current band-by-band
Hmmm,
Given that ham-affordable components are full of minor and harmless
frequency dependent characteristics, INCLUDING the antennas and dummy loads
used, is there really any good reason to EXPECT 1.8-30 power output
uniformity beyond what is commonly measured? Quite contrary to amps which
were designed, built and certified to a broadband tight uniformity (and
appropriately priced), if one WANTS exactly 500.0 watts from a KPA500 for
some purpose, and you actually trust your output measuring instrument to
deliver an accurate measurement to four figures, one just adjusts the
drive, does one not?
This is ham gear, not lab instruments, but I would be intrigued to hear
what purpose this debated level of accuracy serves, other than light
entertainment. I have sometimes heard some very interesting stuff coming
from the other side of what I thought was the left field foul line. One
never knows.
???
73, Guy.
On Tue, Feb 7, 2012 at 3:23 PM, n...@n5ge.com wrote:
Is your dummy load absolutely a flat 1.0:1 from 1.0MHz to 30MHz?
73,
Tom
Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member
Only the white eyes would believe they could cut the top
off a blanket, sew it to the bottom and have a longer
blanket.
-- American Indian comment about Daylight Saving Time --
On Tue, 07 Feb 2012 13:35:47 +, Brian Alsop als...@nc.rr.com wrote:
Guys,
I'm also curious about this-- especially what's going on on 15M.
My values at 500 W out into a dummy load are:
(amp), [volts], {efficiency}
1.8MHz DC (11.5) [63.1] {70}
3.5MHz (11.2) [63.5] {71}
7MHz(12.2) [62.5] {67}
10.1MHz (not measured)
14MHz (13.4)[61.8] {60}
18.1MHz (12.9)[62.8] (63}
21MHz (15.8)[61.2] {52}
24.9MHz (14.6) [60.1] {56}
29.7MHz (14.7)[60.4] {56}
These are in reasonable agreement with David's except for perhaps 10M.
The problem with these measurements are the wattmeter accuracy (10%?)
and the current measurement inaccuracy. Default wattmeter calibration
factors were used above. Elecraft is using a Hall effect device to
measure PA current. It would be nice to know just what accuracy to
expect from it.
The efficiencies appear to be in the right ballpark. They tend to fall
on a straight line log plot vs frequency, decreasing at higher freq's.
If nothing else, the above numbers serve as a benchmark for future
comparisons down the road for my amp.
Note: The current measurement can be significantly affected by RF on the
outside shield of the coax. Until a choke was employed on the feedline,
the 24.9 MHz current with a real antenna measured 3 amps too low. With
the choke it agreed with the above dummy load value. I suspect lots of
KPA-500 users do have this condition-- given the types of
antennas/tuners et al described by uses on this reflector.
73 de Brian/K3KO
On 2/4/2012 20:27, david park wrote:
I have recently assembled KPA500 serial number 641. When testing into
a dummy load I find that I get a large variation in the DC power input when
driving for 500W CW when I go from band to band. My worst band is 21MHz,
where I get the highest current (lowest efficiency). The drive was
adjusted to give 500W as indicated by the LCD display. Here are my
results:-
1.8MHz DC current 10.0Afan hardly ever comes on
3.5MHz DC current 10.0A fan hardly ever comes on
7MHz 12.0A
10.1MHz12.4A
14MHz 14.3A
18.1MHz13.8A
21MHz 16.4A temperature rises rapidly and
fan soon gets to full speed
24.9MHz13.5A
29.7MHz12.3A
I have no results for 50MHz band as I have no transceiver covering that
band.
The readings drift as the heatsink (and the dummy load) warm up, and so
I took readings quickly and allowed time for the heatsink to cool down
between each band. I find that the KPA500 current sensor tends to give low
readings.
I would be interested in knowing how other amplifiers perform.
David Park G3PSV
-
No virus found in this message.
Checked by AVG - www.avg.com
Version: 10.0.1424 / Virus Database: 2112/4794 - Release Date: 02/07/12
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Re: [Elecraft] [QRO] KPA500 variation of PA current band-by-band
On Tue, Feb 7, 2012 at 3:23 PM, n...@n5ge.com wrote: Is your dummy load absolutely a flat 1.0:1 from 1.0MHz to 30MHz? Suppose that the SWR is 1.2. This means that 0.8% of the power is reflected (80 milliwatts reflected for 10 forward). If the SWR is 1.1, the reflected power is 0.2%. A simple coax jumper can sometimes cause an impedance bump large enough to reflect more power than that. A few minutes spent on a test bench with even the fanciest precision equipment will quickly disabuse one of the notion that a dummy load can be trusted to be absolutely flat 1.0:1 from 1.0MHz to 30MHz. Tony KT0NY __ 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
Re: [Elecraft] [QRO] KPA500 variation of PA current band-by-band
Guy and all,
You are so correct. This is ham radio, and precision instrumentation
for power output levels is not the norm - a 20% error potential should
always be considered.
Yes, I personally have power instrumentation that is calibrated to the 5
% level up to 30 MHz. That level of precision has come at a goodly cost
and effort.
In general, amateur quality power measurement gear should be given a +/-
20% range of error. There are variations due to frequency, variations
due to changes in the dummy load actual impedance, and if one is using
an antenna, any common mode RF current can substantially influence the
readings on the meters.
In other words, what you see on your power meter may or may not reflect
reality. If there is any doubt about your results, tell me what your
results are when driving a known good 50 ohm non-reactive dummy load
(measure it with your antenna analyzer), and if a problem is indicated
with that load, then you can conclude that you have a transceiver
problem. If it is OK into that dummy load, but gives problems driving
your antenna, then you will have to solve the problem in your antenna field.
These are generalized statements and not directed at any particular
installation. If you and your indications are suspect, then investigate
your particular situation carefully (it is possible that we can help).
73,
Don W3FPR
On 2/7/2012 9:40 PM, Guy Olinger K2AV wrote:
Hmmm,
Given that ham-affordable components are full of minor and harmless
frequency dependent characteristics, INCLUDING the antennas and dummy loads
used, is there really any good reason to EXPECT 1.8-30 power output
uniformity beyond what is commonly measured? Quite contrary to amps which
were designed, built and certified to a broadband tight uniformity (and
appropriately priced), if one WANTS exactly 500.0 watts from a KPA500 for
some purpose, and you actually trust your output measuring instrument to
deliver an accurate measurement to four figures, one just adjusts the
drive, does one not?
This is ham gear, not lab instruments, but I would be intrigued to hear
what purpose this debated level of accuracy serves, other than light
entertainment. I have sometimes heard some very interesting stuff coming
from the other side of what I thought was the left field foul line. One
never knows.
???
73, Guy.
On Tue, Feb 7, 2012 at 3:23 PM,n...@n5ge.com wrote:
Is your dummy load absolutely a flat 1.0:1 from 1.0MHz to 30MHz?
73,
Tom
Amateur Radio Operator N5GE
ARRL Lifetime Member
QCWA Lifetime Member
Only the white eyes would believe they could cut the top
off a blanket, sew it to the bottom and have a longer
blanket.
-- American Indian comment about Daylight Saving Time --
On Tue, 07 Feb 2012 13:35:47 +, Brian Alsopals...@nc.rr.com wrote:
Guys,
I'm also curious about this-- especially what's going on on 15M.
My values at 500 W out into a dummy load are:
(amp), [volts], {efficiency}
1.8MHz DC (11.5) [63.1] {70}
3.5MHz (11.2) [63.5] {71}
7MHz(12.2) [62.5] {67}
10.1MHz (not measured)
14MHz (13.4)[61.8] {60}
18.1MHz (12.9)[62.8] (63}
21MHz (15.8)[61.2] {52}
24.9MHz (14.6) [60.1] {56}
29.7MHz (14.7)[60.4] {56}
These are in reasonable agreement with David's except for perhaps 10M.
The problem with these measurements are the wattmeter accuracy (10%?)
and the current measurement inaccuracy. Default wattmeter calibration
factors were used above. Elecraft is using a Hall effect device to
measure PA current. It would be nice to know just what accuracy to
expect from it.
The efficiencies appear to be in the right ballpark. They tend to fall
on a straight line log plot vs frequency, decreasing at higher freq's.
If nothing else, the above numbers serve as a benchmark for future
comparisons down the road for my amp.
Note: The current measurement can be significantly affected by RF on the
outside shield of the coax. Until a choke was employed on the feedline,
the 24.9 MHz current with a real antenna measured 3 amps too low. With
the choke it agreed with the above dummy load value. I suspect lots of
KPA-500 users do have this condition-- given the types of
antennas/tuners et al described by uses on this reflector.
73 de Brian/K3KO
__
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Re: [Elecraft] [QRO] KPA500 variation of PA current band-by-band
Tony, All you say is true. and should be heeded by all hams. I have dummy loads that are known to be flat (within 5%) to 1 GHz, and I have several more that are flat to within 500 MHz. Others will display the same characteristics to 60 MHz. I know which ones are which, and I rely on them to give me precision power measurement capability. I do not depend on anything other than the RF voltage measured across that known good dummy load for true calculation of RF power (although I do have one wattmeter calibrated to NIST standards that I use as a secondary standard to calibrate my other meters). In other words, I have become more and more distrustful of in-line wattmeters which may be in error by a substantial amount (20% of the full scale reading) - just try to measure 5 watts with a wattmeter having a 200 watt scale - the error may be as much as 40 watts anywhere on the scale - so a reading of 5 watts might be anywhere between zero and 45 watts actual power - does that seem ridiculous - certainly, but it is true - some wattmeters can be in error by that much when used at levels considerably less than their full scale reading. OK, this is my wattmeter inaccuracy rant for Feb 2012 - thanks for listening. 73, Don W3FPR On 2/7/2012 10:09 PM, Tony Estep wrote: On Tue, Feb 7, 2012 at 3:23 PM,n...@n5ge.com wrote: Is your dummy load absolutely a flat 1.0:1 from 1.0MHz to 30MHz? Suppose that the SWR is 1.2. This means that 0.8% of the power is reflected (80 milliwatts reflected for 10 forward). If the SWR is 1.1, the reflected power is 0.2%. A simple coax jumper can sometimes cause an impedance bump large enough to reflect more power than that. A few minutes spent on a test bench with even the fanciest precision equipment will quickly disabuse one of the notion that a dummy load can be trusted to be absolutely flat 1.0:1 from 1.0MHz to 30MHz. Tony KT0NY __ 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
Re: [Elecraft] [QRO] KPA500 variation of PA current band-by-band
120 or 240 volts supply? On Feb 4, 2012, at 2:27 PM, david park contrast...@yahoo.com wrote: I have recently assembled KPA500 serial number 641. When testing into a dummy load I find that I get a large variation in the DC power input when driving for 500W CW when I go from band to band. My worst band is 21MHz, where I get the highest current (lowest efficiency). The drive was adjusted to give 500W as indicated by the LCD display. Here are my results:- 1.8MHz DC current 10.0Afan hardly ever comes on 3.5MHz DC current 10.0A fan hardly ever comes on 7MHz 12.0A 10.1MHz12.4A 14MHz 14.3A 18.1MHz13.8A 21MHz 16.4A temperature rises rapidly and fan soon gets to full speed 24.9MHz13.5A 29.7MHz12.3A I have no results for 50MHz band as I have no transceiver covering that band. The readings drift as the heatsink (and the dummy load) warm up, and so I took readings quickly and allowed time for the heatsink to cool down between each band. I find that the KPA500 current sensor tends to give low readings. I would be interested in knowing how other amplifiers perform. David Park G3PSV __ 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 __ 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
Re: [Elecraft] [QRO] KPA500 variation of PA current band-by-band
Given that the poster is in the UK can probably assume 240Vac. Regards, Mike VP8NO On 04/02/2012 17:31, Jack Berry wrote: 120 or 240 volts supply? On Feb 4, 2012, at 2:27 PM, david parkcontrast...@yahoo.com wrote: I have recently assembled KPA500 serial number 641. When testing into a dummy load I find that I get a large variation in the DC power input when driving for 500W CW when I go from band to band. My worst band is 21MHz, where I get the highest current (lowest efficiency). The drive was adjusted to give 500W as indicated by the LCD display. Here are my results:- 1.8MHz DC current 10.0Afan hardly ever comes on 3.5MHz DC current 10.0A fan hardly ever comes on 7MHz 12.0A 10.1MHz12.4A 14MHz 14.3A 18.1MHz13.8A 21MHz 16.4A temperature rises rapidly and fan soon gets to full speed 24.9MHz13.5A 29.7MHz12.3A I have no results for 50MHz band as I have no transceiver covering that band. The readings drift as the heatsink (and the dummy load) warm up, and so I took readings quickly and allowed time for the heatsink to cool down between each band. I find that the KPA500 current sensor tends to give low readings. I would be interested in knowing how other amplifiers perform. David Park G3PSV __ 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 __ 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 __ 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
