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KPA-500 watt meter vs. Palstar

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k2zf50

KPA-500 watt meter vs. Palstar

Hi,

My KPA-500 watt meter and my Palstar watt meter read about the same at the higher power readings. But at the 100 watt and lower ranges there is a significant difference. My question is which is the more correct reading at the lower ranges, the Elecraft or Palstar. If I want to calibrate my K3 which one would be more accurate? Being that the Elecraft is a digital display would that one be more accurate?

Thanks,
Jim Douglas K2ZF

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k2zf50

Re: KPA-500 watt meter vs. Palstar

Hi Ray,

Thanks or your response. I have found that on 20 meters my K3 displays a high current warning above 80 watts displayed on the K3. Other bands I can transmit at 100 watts and no high current warning. I believe that is because the watt meter I have been using is not accurate and the K3 may be putting out in excess at this power level displayed on the K3 meter and therefore the high current warning. That is why I was asking which watt meter, the Palstar or the KPA-500 would be more accurate. I understand that 80 watts or 110 watts on the receiving end is not noticeable but I need to know why the high current warning at 80 watts on the K3? Is it the watt meter I am using to calibrate the K3?

Thanks,

Jim Douglas K2ZF

-----Original Message-----
From: Ray Sills <[hidden email]>
To: k2zf50 <[hidden email]>
Sent: Sun, Sep 18, 2011 5:22 am
Subject: Re: [Elecraft] KPA-500 watt meter vs. Palstar

HI Jim:

Well, as always, measuring equipment has to be calibrated, and as
you've noticed, indicated readings can vary over the range of
operation. Most measuring gear for ham use has about a 10% or so
tolerance, plus and minus, so you can't get truly accurate readings.
To get to precision levels, (1% or so), you need very high quality
instruments (meaning expensive), or at least a way of correlating the
indicated readings to a know level of accuracy.

For many hams Bird wattmeters are the reference measurement, but even
they are not highly accurate, and it's often the case that the
accuracy varies over the range of operation. The fact that the
Elecraft unit has a digital display does not mean it's more
accurate. It may be more "precise" (able to finely resolve a
measurement), but that does not mean it's more accurate. A digital
clock that displays seconds is more precise than an analog clock that
has only a minute hand and hour hand, but the digital clock might
have a bad time base and drift enough to gain or lose time in a day.
The analog clock might be rock solid, and very accurate.. just not as
precise.

So, with regard to your measurements... take your pick. If you want
to be a scientist, you can build a dummy load in a can, fill it with
de-ionized (pure) water, and measure the temperature change over
time of the water to determine how many watts are being dissipated.
Then, make a comparison to what the meter says and construct a
calibration chart.

For me, that would be a lot of work. I'd be happy with approximate
readings... if the 100 watt reading is actually 85 watts or 110
watts, it would not bother me. You'd hardly notice the difference at
the receiving end, maybe not at all.

73 de Ray
K2ULR
FN20kf
Warrington, PA

On Sep 18, 2011, at 8:58 AM, [hidden email] wrote:

>
> Hi,
>
>
>
> My KPA-500 watt meter and my Palstar watt meter read about the same
> at the higher power readings. But at the 100 watt and lower ranges
> there is a significant difference. My question is which is the more
> correct reading at the lower ranges, the Elecraft or Palstar. If I
> want to calibrate my K3 which one would be more accurate? Being
> that the Elecraft is a digital display would that one be more
> accurate?
>
>
> Thanks,
> Jim Douglas K2ZF
>
>
> ______________________________________________________________
> 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

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Grant Youngman

Re: KPA-500 watt meter vs. Palstar

If you've run the TX gain calibration, and that worked properly, it sounds more like you have an actual load problem. Which would cause high current.

Is the high current warning happening both with a known good 50 ohm load connected to the K3 and with the antenna?

Sent from my iPhone

On Sep 18, 2011, at 8:45 AM, [hidden email] wrote:

> Hi Ray,
>
>
> Thanks or your response. I have found that on 20 meters my K3 displays a high current warning above 80 watts displayed on the K3. Other bands I can transmit at 100 watts and no high current warning. I believe that is because the watt meter I have been using is not accurate and the K3 may be putting out in excess at this power level displayed on the K3 meter and therefore the high current warning.
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k2zf50

Re: KPA-500 watt meter vs. Palstar

The high current warning on 20 meters happens with either a dummy load or my antenna's through an antenna tuner. It happens only on 20 meters and over 80 watts. If I set the K3 for more than 80 watts the output of the K3 goes into oscillation evident on the K3 watt meter. Lower than 80 watts everything is OK. The TX gain calibration is good.

Thanks,

Jim K2ZF

-----Original Message-----
From: Grant Youngman <[hidden email]>
To: elecraft <[hidden email]>
Sent: Sun, Sep 18, 2011 6:20 am
Subject: Re: [Elecraft] KPA-500 watt meter vs. Palstar

If you've run the TX gain calibration, and that worked properly, it sounds more
like you have an actual load problem. Which would cause high current.

Is the high current warning happening both with a known good 50 ohm load
connected to the K3 and with the antenna?

Sent from my iPhone

On Sep 18, 2011, at 8:45 AM, [hidden email] wrote:

> Hi Ray,
>
>
> Thanks or your response. I have found that on 20 meters my K3 displays a high
current warning above 80 watts displayed on the K3. Other bands I can transmit
at 100 watts and no high current warning. I believe that is because the watt
meter I have been using is not accurate and the K3 may be putting out in excess
at this power level displayed on the K3 meter and therefore the high current
warning.
______________________________________________________________
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w0mu

Re: KPA-500 watt meter vs. Palstar

Sounds like RF. Are all the pl259's and other cabling tight etc?

We were having some strange problems with our Fire radio at the station
and somehow the connector on the back was nearly off. Screwing it back
on solved a bunch of strange oddities that were happening in the comm room.

On 9/18/2011 8:37 AM, [hidden email] wrote:

> The high current warning on 20 meters happens with either a dummy load or my antenna's through an antenna tuner. It happens only on 20 meters and over 80 watts. If I set the K3 for more than 80 watts the output of the K3 goes into oscillation evident on the K3 watt meter. Lower than 80 watts everything is OK. The TX gain calibration is good.
>
>
> Thanks,
>
> Jim K2ZF
>
>
>
>
>
>
> -----Original Message-----
> From: Grant Youngman<[hidden email]>
> To: elecraft<[hidden email]>
> Sent: Sun, Sep 18, 2011 6:20 am
> Subject: Re: [Elecraft] KPA-500 watt meter vs. Palstar
>
> If you've run the TX gain calibration, and that worked properly, it sounds more
> like you have an actual load problem. Which would cause high current.
>
> Is the high current warning happening both with a known good 50 ohm load
> connected to the K3 and with the antenna?
>
> Sent from my iPhone
>
> On Sep 18, 2011, at 8:45 AM, [hidden email] wrote:
>
>> Hi Ray,
>>
>>
>> Thanks or your response. I have found that on 20 meters my K3 displays a high
> current warning above 80 watts displayed on the K3. Other bands I can transmit
> at 100 watts and no high current warning. I believe that is because the watt
> meter I have been using is not accurate and the K3 may be putting out in excess
> at this power level displayed on the K3 meter and therefore the high current
> warning.
> ______________________________________________________________
> 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
>
>
> ______________________________________________________________
> 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

--
J6/W0MU November 21 - December 1 2011 CQ WW DX CW

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k2zf50

Re: KPA-500 watt meter vs. Palstar

All connections are tight. I have substituted coax to address that concern. Its funny it happens only on 20 meters into a dummy load or antenna and tuner.

-----Original Message-----
From: Mike Fatchett W0MU <[hidden email]>
To: k2zf50 <[hidden email]>; elecraft <[hidden email]>
Sent: Sun, Sep 18, 2011 6:58 am
Subject: Re: [Elecraft] KPA-500 watt meter vs. Palstar

Sounds like RF. Are all the pl259's and other cabling tight etc?

We were having some strange problems with our Fire radio at the station
and somehow the connector on the back was nearly off. Screwing it back
on solved a bunch of strange oddities that were happening in the comm room.

On 9/18/2011 8:37 AM, [hidden email] wrote:
> The high current warning on 20 meters happens with either a dummy load or my
antenna's through an antenna tuner. It happens only on 20 meters and over 80
watts. If I set the K3 for more than 80 watts the output of the K3 goes into
oscillation evident on the K3 watt meter. Lower than 80 watts everything is OK.
The TX gain calibration is good.

>
>
> Thanks,
>
> Jim K2ZF
>
>
>
>
>
>
> -----Original Message-----
> From: Grant Youngman<[hidden email]>
> To: elecraft<[hidden email]>
> Sent: Sun, Sep 18, 2011 6:20 am
> Subject: Re: [Elecraft] KPA-500 watt meter vs. Palstar
>
> If you've run the TX gain calibration, and that worked properly, it sounds

> like you have an actual load problem. Which would cause high current.
>
> Is the high current warning happening both with a known good 50 ohm load
> connected to the K3 and with the antenna?
>
> Sent from my iPhone
>
> On Sep 18, 2011, at 8:45 AM, [hidden email] wrote:
>
>> Hi Ray,
>>
>>
>> Thanks or your response. I have found that on 20 meters my K3 displays a high
> current warning above 80 watts displayed on the K3. Other bands I can transmit
> at 100 watts and no high current warning. I believe that is because the watt
> meter I have been using is not accurate and the K3 may be putting out in

excess

> at this power level displayed on the K3 meter and therefore the high current
> warning.
> ______________________________________________________________
> 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
>
>
> ______________________________________________________________
> 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

Tony Estep

Re: KPA-500 watt meter vs. Palstar

On Sun, Sep 18, 2011 at 10:25 AM, <[hidden email]> wrote:

> ... it happens only on 20 meters into a dummy load...

=============
Maybe you can put a scope across the dummy load and calibrate your power
output that way. That has worked for me.

Tony KT0NY

--
http://www.isb.edu/faculty/facultydir.aspx?ddlFaculty=352
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Don Wilhelm-4

Re: KPA-500 watt meter vs. Palstar

In reply to this post by k2zf50

Jim,

Being one not to trust any instrument until it has proven its worth (and
calibration), I would not trust either until calibrated.

OK, that brings up the question of how to do a meaningful calibration.
I connect to a known good (precision) 50 ohm dummy load, and read the RF
voltage at the dummy load with my oscilloscope equipped with an RF
Probe. A coax TEE adapter placed at the dummy load will give you access
to the center conductor. Make certain the 'scope and probe are rated
for greater than 5 times the frequency at which you are doing the
measurement.

A quick and easy formula is to measure the peak to peak RF voltage,
square it and divide by 400.
Quicker and more accurate than doing conversion to RMS and then
calculating - a lot of terms cancel out if you want to attempt to derive
my formula yourself.

Note that many analog wattmeters are only spec'ed for 20% of the full
scale reading. On a 200 watt scale, that means it can be off by 40
watts at any point on the dial. Even the much revered Bird wattmeter is
only to be trusted to 5% of the full scale reading, and that is only
after lab calibration - so with a 100 watt slug, even the Bird can be in
error by as much as 5 watts at any point on the scale. The precision
dummy load and the 'scope can do 5% or better at the level being
measured - i.e. at 5 watts, you may have a 0.25 watt error, and at 50
watts you may have a 2.5 watt error, but that is much better than a
typical analog wattmeter.

73,
Don W3FPR

On 9/18/2011 8:58 AM, [hidden email] wrote:

> Hi,
>
>
>
> My KPA-500 watt meter and my Palstar watt meter read about the same at the higher power readings. But at the 100 watt and lower ranges there is a significant difference. My question is which is the more correct reading at the lower ranges, the Elecraft or Palstar. If I want to calibrate my K3 which one would be more accurate? Being that the Elecraft is a digital display would that one be more accurate?
>
>
> Thanks,
> Jim Douglas K2ZF
>
>
> ______________________________________________________________
> 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
>

k6dgw

Re: KPA-500 watt meter vs. Palstar

On 9/18/2011 10:57 AM, Don Wilhelm wrote:

> Being one not to trust any instrument until it has proven its worth (and
> calibration), I would not trust either until calibrated.

Calibration sticker on it or not, in the final analysis, the only place
a meter can be known to be accurate [unless not working at all], is when
it reads zero.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org
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