[Elecraft] Question about K2 power meter

Discussion:

Jeff Kinzli N6GQ

2007-04-23 01:13:03 UTC

Don and others,

A few weeks back, a user posted about an issue with low power output

If you do not have either the KAT2, the KPA100, or the KAT100 installed, the
K2 does not display the actual power output on the LCD (the requested power
is displayed briefly when the power control is changed). What is the
indication on the LED bargraph during transmit?

I'm going through an issue with my K2 where it *appears* to be putting
out too much power. With the KPA100 installed, the output sometimes
jumps up to 150+W.

I removed the KPA100 from the picture and have been seeing if I can
reproduce higher than normal output with just the base K2. So far, the
behavior is that if I enter TUNE mode, the indicated power on the
display of the K2 will rise to 16-17W. My watt meter isn't accurate
enough to tell me what it's *really* putting out though, although with
the KPA100 it is accurate enough to see the 150W+ peaks.

So I was trying to think if it's really putting out 16+W, or if the
power meter is really telling me it's TRYING to put it out (because my
external wattmeter looks like actually less, but again not accurate).

I also thought maybe it's an ALC issue, because if I rotate the power
knob back then back up to max, the indicated power on the K2 will go
to about 15W, but the next time I do TUNE again, it again goes back up
to 16+W.

Any thoughts on this? Should I keep chasing ALC issues? I've already
gone through the base K2 RF board resoldering T1-T4, reheating
anything that looks suspect, etc. to no avail.

I also sent something to this effect to ***@Support, I'm just hoping
someone might have any ideas that I could chase down.

Thanks,

Jeff

Don Wilhelm

2007-04-23 01:37:27 UTC

Permalink

Jeff,

Is this into an antenna or into a dummy load? If it is into an antenna,
'strange things can happen' in the basic K2 configuration when the
antenna is not 50 ohms pure resistive.

Work into a dummy load first to resolve the situation (or answer your
questions). The LED bargraph should be fairly accurate (but it only
goes up to 10 watts).

If your external wattmeter does not give a good indication at a 5 to 10
watt level, you may find success in measuring the RF voltage across the
dummy load with the RF probe, then calculating the power output from the
voltage (P=V^2/R if your probe reads RF volts RMS - the one provided
with the K2 does read RMS voltage). A high range external wattmeter can
be really far off when indicating lower powers - 20% of the full range
value is a common spec for wattmeter accuracy, and on a 200 watt scale,
that is 40 watts potential error!

Yes, stick with the basic K2 until you can answer the question of how
much power is actually being developed. Once you determine that, you
can chase the cause of the problem if one exists. Don't jump to
conclusions before knowing the answer to this part of the question.

73,
Don W3FPR

Post by Jeff Kinzli N6GQ
Don and others,
A few weeks back, a user posted about an issue with low power output

If you do not have either the KAT2, the KPA100, or the KAT100
installed, the
K2 does not display the actual power output on the LCD (the requested power
is displayed briefly when the power control is changed). What is the
indication on the LED bargraph during transmit?

I'm going through an issue with my K2 where it *appears* to be putting
out too much power. With the KPA100 installed, the output sometimes
jumps up to 150+W.
I removed the KPA100 from the picture and have been seeing if I can
reproduce higher than normal output with just the base K2. So far, the
behavior is that if I enter TUNE mode, the indicated power on the
display of the K2 will rise to 16-17W. My watt meter isn't accurate
enough to tell me what it's *really* putting out though, although with
the KPA100 it is accurate enough to see the 150W+ peaks.
So I was trying to think if it's really putting out 16+W, or if the
power meter is really telling me it's TRYING to put it out (because my
external wattmeter looks like actually less, but again not accurate).
I also thought maybe it's an ALC issue, because if I rotate the power
knob back then back up to max, the indicated power on the K2 will go
to about 15W, but the next time I do TUNE again, it again goes back up
to 16+W.
Any thoughts on this? Should I keep chasing ALC issues? I've already
gone through the base K2 RF board resoldering T1-T4, reheating
anything that looks suspect, etc. to no avail.
someone might have any ideas that I could chase down.
Thanks,
Jeff
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Don Wilhelm

2007-04-23 01:44:14 UTC

Permalink

Jeff,

Another thought and a question - does the K2 control power properly
(check with TUNE) when the requested power is set to 5 watts? If you
get somewhere between 4.5 and 5.5 watts output with the requested power
set to 5, then the power control circuits are working as they should be.

Setting the power to maximum will not readily reveal any problems with
the power control.

OTOH, if the power output is always high then you do have a problem in
the power control (ALC) loop.

73,
Don W3FPR

Post by Jeff Kinzli N6GQ
Don and others,
A few weeks back, a user posted about an issue with low power output

If you do not have either the KAT2, the KPA100, or the KAT100
installed, the
K2 does not display the actual power output on the LCD (the requested power
is displayed briefly when the power control is changed). What is the
indication on the LED bargraph during transmit?

I'm going through an issue with my K2 where it *appears* to be putting
out too much power. With the KPA100 installed, the output sometimes
jumps up to 150+W.
I removed the KPA100 from the picture and have been seeing if I can
reproduce higher than normal output with just the base K2. So far, the
behavior is that if I enter TUNE mode, the indicated power on the
display of the K2 will rise to 16-17W. My watt meter isn't accurate
enough to tell me what it's *really* putting out though, although with
the KPA100 it is accurate enough to see the 150W+ peaks.
So I was trying to think if it's really putting out 16+W, or if the
power meter is really telling me it's TRYING to put it out (because my
external wattmeter looks like actually less, but again not accurate).
I also thought maybe it's an ALC issue, because if I rotate the power
knob back then back up to max, the indicated power on the K2 will go
to about 15W, but the next time I do TUNE again, it again goes back up
to 16+W.
Any thoughts on this? Should I keep chasing ALC issues? I've already
gone through the base K2 RF board resoldering T1-T4, reheating
anything that looks suspect, etc. to no avail.
someone might have any ideas that I could chase down.
Thanks,
Jeff
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Jeff Kinzli N6GQ

2007-04-23 04:56:21 UTC

Permalink

Hi Don,

Thanks for the replies.

To answer your questions, the problem occurs into a dummy load.

I set the base K2 (without KPA100 connected) to 5.0W, and then TUNE,
and it starts at 5.0W and heads upwards to 5.7-6.0W (read from the
display, as well as the S-meter). After about 10 seconds in TUNE, it's
up to 5.7 or 6W and the next LED on the S-meter is starting to flicker
some.

Moving the power knob will allow me to bring it back to 5.0W, but the
next TUNE will see the power climb back up again.

I'm not sure if I should still be looking on the RF board at this
point, or start focusing on the control board...?

Thanks, 73,

Jeff

Post by Don Wilhelm
Jeff,
Another thought and a question - does the K2 control power properly
(check with TUNE) when the requested power is set to 5 watts? If you
get somewhere between 4.5 and 5.5 watts output with the requested power
set to 5, then the power control circuits are working as they should be.
Setting the power to maximum will not readily reveal any problems with
the power control.
OTOH, if the power output is always high then you do have a problem in
the power control (ALC) loop.
73,
Don W3FPR

Post by Jeff Kinzli N6GQ
Don and others,
A few weeks back, a user posted about an issue with low power output

I'm going through an issue with my K2 where it *appears* to be putting
out too much power. With the KPA100 installed, the output sometimes
jumps up to 150+W.
I removed the KPA100 from the picture and have been seeing if I can
reproduce higher than normal output with just the base K2. So far, the
behavior is that if I enter TUNE mode, the indicated power on the
display of the K2 will rise to 16-17W. My watt meter isn't accurate
enough to tell me what it's *really* putting out though, although with
the KPA100 it is accurate enough to see the 150W+ peaks.
So I was trying to think if it's really putting out 16+W, or if the
power meter is really telling me it's TRYING to put it out (because my
external wattmeter looks like actually less, but again not accurate).
I also thought maybe it's an ALC issue, because if I rotate the power
knob back then back up to max, the indicated power on the K2 will go
to about 15W, but the next time I do TUNE again, it again goes back up
to 16+W.
Any thoughts on this? Should I keep chasing ALC issues? I've already
gone through the base K2 RF board resoldering T1-T4, reheating
anything that looks suspect, etc. to no avail.
someone might have any ideas that I could chase down.
Thanks,
Jeff
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Don Wilhelm

2007-04-23 13:20:33 UTC

Permalink

Jeff,

That is normal behavior - the power will climb a bit if left in TUNE for
a period of time. It is mostly the result of heating in the PA
transistors. In normal operation, either with CW or SSB, there is not a
constant carrier being transmitted and the same conditions will not be
present.

Do not leave the K2 in TUNE at high power for any significant length of
time - remember that TUNE is transmitting at a 100% duty cycle. OK for
short bursts, but not good for longer periods. The base K2 shoud be
limited to 5 watts or less for a 100% duty cycle transmission and to 35
watts or less with the KPA100.

73,
Don W3FPR

Post by Jeff Kinzli N6GQ
Hi Don,
Thanks for the replies.
To answer your questions, the problem occurs into a dummy load.
I set the base K2 (without KPA100 connected) to 5.0W, and then TUNE,
and it starts at 5.0W and heads upwards to 5.7-6.0W (read from the
display, as well as the S-meter). After about 10 seconds in TUNE, it's
up to 5.7 or 6W and the next LED on the S-meter is starting to flicker
some.
Moving the power knob will allow me to bring it back to 5.0W, but the
next TUNE will see the power climb back up again.
I'm not sure if I should still be looking on the RF board at this
point, or start focusing on the control board...?
Thanks, 73,
Jeff

Post by Jeff Kinzli N6GQ
Don and others,
A few weeks back, a user posted about an issue with low power output

I'm going through an issue with my K2 where it *appears* to be putting
out too much power. With the KPA100 installed, the output sometimes
jumps up to 150+W.
I removed the KPA100 from the picture and have been seeing if I can
reproduce higher than normal output with just the base K2. So far, the
behavior is that if I enter TUNE mode, the indicated power on the
display of the K2 will rise to 16-17W. My watt meter isn't accurate
enough to tell me what it's *really* putting out though, although with
the KPA100 it is accurate enough to see the 150W+ peaks.
So I was trying to think if it's really putting out 16+W, or if the
power meter is really telling me it's TRYING to put it out (because my
external wattmeter looks like actually less, but again not accurate).
I also thought maybe it's an ALC issue, because if I rotate the power
knob back then back up to max, the indicated power on the K2 will go
to about 15W, but the next time I do TUNE again, it again goes back up
to 16+W.
Any thoughts on this? Should I keep chasing ALC issues? I've already
gone through the base K2 RF board resoldering T1-T4, reheating
anything that looks suspect, etc. to no avail.
someone might have any ideas that I could chase down.
Thanks,
Jeff
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Jeff Kinzli N6GQ

2007-04-23 14:21:49 UTC

Permalink

Thanks Don and others for the answers.

In my case, I'm trying to run down a proble where the KPA100 will be
fine, then all of a sudden it's output will jump up over 140W. I
thought that the high output in the base K2 might be the cause. So are
we saying that some variation is ok, and once in a while if the KPA100
gets up over 150W then we're ok? This is not apparently an oscillation
issue, as I don't see high SWRs.

Thanks,

Jeff

Post by Don Wilhelm
Jeff,
That is normal behavior - the power will climb a bit if left in TUNE for
a period of time. It is mostly the result of heating in the PA
transistors. In normal operation, either with CW or SSB, there is not a
constant carrier being transmitted and the same conditions will not be
present.
Do not leave the K2 in TUNE at high power for any significant length of
time - remember that TUNE is transmitting at a 100% duty cycle. OK for
short bursts, but not good for longer periods. The base K2 shoud be
limited to 5 watts or less for a 100% duty cycle transmission and to 35
watts or less with the KPA100.
73,
Don W3FPR

Post by Jeff Kinzli N6GQ
Don and others,
A few weeks back, a user posted about an issue with low power output

I'm going through an issue with my K2 where it *appears* to be putting
out too much power. With the KPA100 installed, the output sometimes
jumps up to 150+W.
I removed the KPA100 from the picture and have been seeing if I can
reproduce higher than normal output with just the base K2. So far, the
behavior is that if I enter TUNE mode, the indicated power on the
display of the K2 will rise to 16-17W. My watt meter isn't accurate
enough to tell me what it's *really* putting out though, although with
the KPA100 it is accurate enough to see the 150W+ peaks.
So I was trying to think if it's really putting out 16+W, or if the
power meter is really telling me it's TRYING to put it out (because my
external wattmeter looks like actually less, but again not accurate).
I also thought maybe it's an ALC issue, because if I rotate the power
knob back then back up to max, the indicated power on the K2 will go
to about 15W, but the next time I do TUNE again, it again goes back up
to 16+W.
Any thoughts on this? Should I keep chasing ALC issues? I've already
gone through the base K2 RF board resoldering T1-T4, reheating
anything that looks suspect, etc. to no avail.
someone might have any ideas that I could chase down.
Thanks,
Jeff
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Don Wilhelm

2007-04-23 14:54:46 UTC

Permalink

Jeff,

If you are saying that you see an occasional jump from 120 watts power
to 140 or even 160, I would say that *MAY* be possible, but if it jumps
from 50 (or even 80) watts to 160, then you do have a problem - and my
first reaction is that it is an indication of a transient oscillation.

How long does the power stay at 160 watts? Is this on 40 meters, or
does it occur on all bands? What level is your KPA100? If it has RFC10
installed and the L15 position has a toroid and L16 has a toroid with a
red core - you do not have the latest update - that update was designed
to combat a parasitic on 40 meters. In your case, I would recommend the
KPA100UPKT if it is not already installed just to be rid of the
possibility that the 40 meter parasitic is what is causing your problem.

73,
Don W3FPR

Post by Jeff Kinzli N6GQ
Thanks Don and others for the answers.
In my case, I'm trying to run down a proble where the KPA100 will be
fine, then all of a sudden it's output will jump up over 140W. I
thought that the high output in the base K2 might be the cause. So are
we saying that some variation is ok, and once in a while if the KPA100
gets up over 150W then we're ok? This is not apparently an oscillation
issue, as I don't see high SWRs.
Thanks,
Jeff

power