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K2 power out accurate?

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David Dietrich

K2 power out accurate?

Hello All!

My friend and I spent yesterday aligning my Norcal 40A and recently finished K2/10 #7164. We really did not play too much with the K2 after we finished aligning as we were also working on some other things in my shack.

When I was starting to really get to know the ins and outs of the radio, I noticed that the power out indicated on the display when you adjust the power knob is much higher as indicated on my QRP Wattmeter. I set the radio to around 2.0 W, and the Wattmeter is showing around 5W. When I was at about 5-6 W, I pinned the needle on the Wattmeter. We followed the manual to a "T" and used a frequency counter, my Wattmeter, a 'scope, and signal generator to do the alignment.

Any ideas?

Thanks & 73,

David
KC9EHQ
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Chip Stratton

Re: K2 power out accurate?

Well there you go. You used far too may sophisticated instruments to align
it, and it isn't happy.

My K2 with KAT2 are reasonably is reasonably close, but set at 5.0 watts it
puts out 3.2 watts, and set at 5.3 watts its putting out 6 watts, so it
isn't exactly linear.

Chip AE5KA
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Don Wilhelm-4

Re: K2 power out accurate?

In reply to this post by David Dietrich

David,

Yes, I have several "ideas". First of all, how confident are you of
your QRP wattmeter readings? Know that typical wattmeters can be in
error by as much as 20% of full scale - if the full scale is 10 watts,
that is a 2 watt potential error *anywhere* on the meter scale.
Secondly, what is the actual impedance of your dummy load?

If your dummy load is a good 50 ohm resistive load, I would state that
the K2 power indication is more accurate than any external wattmeter -
OTOH, if the dummy load is not 50 ohms resistive (check with an antenna
analyzer), then your readings can be "all over the map".

The base K2 power output reading is only accurate if you are driving a
load that is 50+j0 - in other words, a perfect 50 ohm load. If one adds
the KAT2 or the KAT100 or the KPA100, then that situation changes
because those options add a real wattmeter - the basic K2 uses an RF
voltage detector which is accurate, but only into a 50 ohm resistive
load. In all my testing of the K2 (going on 7 years now), I have found
that the K2 power indication is better than most wattmeters - given the
condition that the dummy load is a good 50 ohm pure resistive load - in
other words, a precision dummy load.

Sources of dummy loads meeting my requirements for measurement accuracy,
try Ridge Equipment https://www.ridgeequipment.com/store/index.html.
They have dummy loads accurate enough for measurement purposes - many
"dummy loads" are sufficient for providing a load on a transceiver, but
may not be of "measurement quality".

73,
Don W3FPR

On 1/10/2012 6:23 PM, David Dietrich wrote:

> Hello All!
>
> My friend and I spent yesterday aligning my Norcal 40A and recently finished K2/10 #7164. We really did not play too much with the K2 after we finished aligning as we were also working on some other things in my shack.
>
> When I was starting to really get to know the ins and outs of the radio, I noticed that the power out indicated on the display when you adjust the power knob is much higher as indicated on my QRP Wattmeter. I set the radio to around 2.0 W, and the Wattmeter is showing around 5W. When I was at about 5-6 W, I pinned the needle on the Wattmeter. We followed the manual to a "T" and used a frequency counter, my Wattmeter, a 'scope, and signal generator to do the alignment.
>
>
> Any ideas?
>
> Thanks& 73,
>
> David
> KC9EHQ
>

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David Dietrich

Re: K2 power out accurate?

Hi Don!

As always, thanks for the reply and info...Much appreciated. I am fairly confident of the Wattmeter's readings. It is an Oak Hills Research QRP Wattmeter. I spent a good 1/2 hour getting the correct readings for alignment with my DMM once the kit was finished. My dummy load is from Oak Hills Research as well, and I built it right around the time I built the Wattmeter this past spring. Again, when I made my final measurements with my DMM, I got a reading of 49.9 Ohms.

Concerning the Wattmeter, I checked power readings into the Wattmeter using the load with my other HF gear. My Norcal 40A was reading 3 W at key down, my Yaesu was reading within a Watt of the meter, and so was my ICOM. I checked my ICOM against my antenna tuner too, and it was almost spot on. However, I did notice that my K1 was only putting out 1 W per the meter at full drive, but that is an issue for another thread.

I was in CW mode when I was noticing this. My K2/10 has the KAT2 installed. I am just wondering if we did something wrong yesterday. We spent a good 3 hours on the procedure.

73,

David
KC9EHQ

________________________________
From: Don Wilhelm <[hidden email]>
To: David Dietrich <[hidden email]>
Cc: "[hidden email]" <[hidden email]>
Sent: Tuesday, January 10, 2012 6:03 PM
Subject: Re: [Elecraft] K2 power out accurate?

David,

Yes, I have several "ideas". First of all, how confident are you of your QRP wattmeter readings? Know that typical wattmeters can be in error by as much as 20% of full scale - if the full scale is 10 watts, that is a 2 watt potential error *anywhere* on the meter scale. Secondly, what is the actual impedance of your dummy load?

If your dummy load is a good 50 ohm resistive load, I would state that the K2 power indication is more accurate than any external wattmeter - OTOH, if the dummy load is not 50 ohms resistive (check with an antenna analyzer), then your readings can be "all over the map".

The base K2 power output reading is only accurate if you are driving a load that is 50+j0 - in other words, a perfect 50 ohm load. If one adds the KAT2 or the KAT100 or the KPA100, then that situation changes because those options add a real wattmeter - the basic K2 uses an RF voltage detector which is accurate, but only into a 50 ohm resistive load. In all my testing of the K2 (going on 7 years now), I have found that the K2 power indication is better than most wattmeters - given the condition that the dummy load is a good 50 ohm pure resistive load - in other words, a precision dummy load.

Sources of dummy loads meeting my requirements for measurement accuracy, try Ridge Equipment https://www.ridgeequipment.com/store/index.html. They have dummy loads accurate enough for measurement purposes - many "dummy loads" are sufficient for providing a load on a transceiver, but may not be of "measurement quality".

73,
Don W3FPR

On 1/10/2012 6:23 PM, David Dietrich wrote:

David Dietrich

K2 power out accurate? (UPDATE/CLARIFICATION)

Evening All,

I neglected to mention this one piece of information with my issue on the K2/10. The pinning of my Wattmeter happens when I have the K2 connected to my outside antenna in this order: K2 to Wattmeter to outside antenna. This is after I do a tune and get a low SWR. My K2 DOES have the KAT2 tuner installed. My antenna is a simple G5RV Jr. I originally said that I had it connected to a dummy load and that was happening. Sorry about that.

I did connect the K2 to my Wattmeter, and then to my Dummy Load, and power output was within a Watt or so on different power settings. So, that tells me the Wattmeter is calibrated within tolerances and the power out appears to be accurate. I also verified this with my other HF radios, both kit AND commercially produced.

Still, I wonder what would cause my Wattmeter to be pinned at 5W when transmitting into an actual antenna?

The Wattmeter is the QRP Wattmeter from Oak Hills Research, and the 100 W dummy load is from them as well.

73,

David
KC9EHQ
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Don Wilhelm-4

Re: K2 power out accurate?

In reply to this post by David Dietrich

David,

OK on your wattmeter and dummy load.
Since you have the KAT2 installed in your K2, check the wattmeter
balance (null adjustment), and then calibrate the forward power so it
agrees with your wattmeter.
If you have the KAT1 installed in your K1, the same thing applies -
those wattmeters must be calibrated against some instrument that you can
trust for accuracy. Your response indicates that you are willing to
trust your OHR QRP Wattmeter, so use that as your "standard".
Keep the cable between the K2, the wattmeter, and the dummy load to a
minimum when making those adjustments - zero length is good. When doing
the balance adjustment, connect the K2 directly to the dummy load.

73,
Don W3FPR

On 1/10/2012 9:05 PM, David Dietrich wrote:

> Hi Don!
>
> As always, thanks for the reply and info...Much appreciated. I am fairly confident of the Wattmeter's readings. It is an Oak Hills Research QRP Wattmeter. I spent a good 1/2 hour getting the correct readings for alignment with my DMM once the kit was finished. My dummy load is from Oak Hills Research as well, and I built it right around the time I built the Wattmeter this past spring. Again, when I made my final measurements with my DMM, I got a reading of 49.9 Ohms.
>
> Concerning the Wattmeter, I checked power readings into the Wattmeter using the load with my other HF gear. My Norcal 40A was reading 3 W at key down, my Yaesu was reading within a Watt of the meter, and so was my ICOM. I checked my ICOM against my antenna tuner too, and it was almost spot on. However, I did notice that my K1 was only putting out 1 W per the meter at full drive, but that is an issue for another thread.
>
>
> I was in CW mode when I was noticing this. My K2/10 has the KAT2 installed. I am just wondering if we did something wrong yesterday. We spent a good 3 hours on the procedure.
>
>
> 73,
>
> David
> KC9EHQ
>
>
>
> ________________________________
> From: Don Wilhelm<[hidden email]>
> To: David Dietrich<[hidden email]>
> Cc: "[hidden email]"<[hidden email]>
> Sent: Tuesday, January 10, 2012 6:03 PM
> Subject: Re: [Elecraft] K2 power out accurate?
>
> David,
>
> Yes, I have several "ideas". First of all, how confident are you of your QRP wattmeter readings? Know that typical wattmeters can be in error by as much as 20% of full scale - if the full scale is 10 watts, that is a 2 watt potential error *anywhere* on the meter scale. Secondly, what is the actual impedance of your dummy load?
>
> If your dummy load is a good 50 ohm resistive load, I would state that the K2 power indication is more accurate than any external wattmeter - OTOH, if the dummy load is not 50 ohms resistive (check with an antenna analyzer), then your readings can be "all over the map".
>
> The base K2 power output reading is only accurate if you are driving a load that is 50+j0 - in other words, a perfect 50 ohm load. If one adds the KAT2 or the KAT100 or the KPA100, then that situation changes because those options add a real wattmeter - the basic K2 uses an RF voltage detector which is accurate, but only into a 50 ohm resistive load. In all my testing of the K2 (going on 7 years now), I have found that the K2 power indication is better than most wattmeters - given the condition that the dummy load is a good 50 ohm pure resistive load - in other words, a precision dummy load.
>
> Sources of dummy loads meeting my requirements for measurement accuracy, try Ridge Equipment https://www.ridgeequipment.com/store/index.html. They have dummy loads accurate enough for measurement purposes - many "dummy loads" are sufficient for providing a load on a transceiver, but may not be of "measurement quality".
>
> 73,
> Don W3FPR
>
> On 1/10/2012 6:23 PM, David Dietrich wrote:
>> Hello All!
>>
>> My friend and I spent yesterday aligning my Norcal 40A and recently finished K2/10 #7164. We really did not play too much with the K2 after we finished aligning as we were also working on some other things in my shack.
>>
>> When I was starting to really get to know the ins and outs of the radio, I noticed that the power out indicated on the display when you adjust the power knob is much higher as indicated on my QRP Wattmeter. I set the radio to around 2.0 W, and the Wattmeter is showing around 5W. When I was at about 5-6 W, I pinned the needle on the Wattmeter. We followed the manual to a "T" and used a frequency counter, my Wattmeter, a 'scope, and signal generator to do the alignment.
>>
>> Any ideas?
>>
>> Thanks& 73,
>>
>> David
>> KC9EHQ
>>
> ______________________________________________________________
> 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
>

Don Wilhelm-4

Re: K2 power out accurate? (UPDATE/CLARIFICATION)

In reply to this post by David Dietrich

David,

That piece of information indicates to me that your wattmeter is not
accurate for power readings when the impedance is not 50 ohms.

You have the KAT2, and I presume you have calibrated it to agree with
your QRP Wattmeter when it is connected to a 50 ohm load.

The KAT2 does not change anything on the antenna side, it only creates a
low SWR on its input side so the K2 PA transistors are "happy" - there
will be no change of the antenna SWR (which is what the wattmeter is
reading).

With your report, I would hesitate to trust the reading of your QRP
Wattmeter when it is connected to something other than a 50 ohm
resistive load.

73,
Don W3FPR

On 1/10/2012 11:46 PM, David Dietrich wrote:

> Evening All,
>
> I neglected to mention this one piece of information with my issue on the K2/10. The pinning of my Wattmeter happens when I have the K2 connected to my outside antenna in this order: K2 to Wattmeter to outside antenna. This is after I do a tune and get a low SWR. My K2 DOES have the KAT2 tuner installed. My antenna is a simple G5RV Jr. I originally said that I had it connected to a dummy load and that was happening. Sorry about that.
>
> I did connect the K2 to my Wattmeter, and then to my Dummy Load, and power output was within a Watt or so on different power settings. So, that tells me the Wattmeter is calibrated within tolerances and the power out appears to be accurate. I also verified this with my other HF radios, both kit AND commercially produced.
>
> Still, I wonder what would cause my Wattmeter to be pinned at 5W when transmitting into an actual antenna?
>
> The Wattmeter is the QRP Wattmeter from Oak Hills Research, and the 100 W dummy load is from them as well.
>