[Elecraft] K2 K2/100 post FD review

[Don Wilhelm]

Mike,

It is not reasonable to expect a normal wattmeter to have greater than a 
10% accuracy.
Consider that the spec for a Bird wattmeter is only 5% right after 
calibration.
Digital wattmeters can be much more accurate, such as the LP-100 from 
Telepostinc, but they are calibrated to NIST traceable standards.

73,
Don W3FPR

On 6/29/2020 8:50 AM, Mike Kopacki wrote:
> Okay. I will go back to your first reply and run through the items you suggested.
>
> Does the fact that on 40 and 80 meters, when I set the requested power to 100w, I actually see a little more - like 103w - but the power drops off on other bands - is that a clue to anything?
>
> Thanks,
> Mike NJ2OM
>
>> On Jun 28, 2020, at 10:50 PM, Don Wilhelm <donwilh at embarqmail.com> wrote:
>>
>> Mike,
>>
>> No, the KPA100 wattmeter will display the actual power being produced if it is well calibrated.
>> That is not necessarily the same as the requested power, although with a properly working KPA100 and a calibrated KPA100 wattmeter, the reading should be the same.
>>
>> 73,
>> Don W3FPR
>>
>>> On 6/28/2020 9:41 PM, Mike Kopacki wrote:
>>> I can run through some of the items you suggest. But I don’t have an external wattmeter that can measure 100 watts. I do have a QRP wattmeter.
>>>
>>> I will start tomorrow to try and work through the question.
>>>
>>> But to be completely accurate...you are saying that the KPA100 wattmeter (which is what I see when pressing TUNE and DISPLAY together), should read the same as the REQUESTED power (which is what the power knob sets)?
>>>
>>> Thanks,
>>> Mike NJ2OM
>>>
>>>>> On Jun 28, 2020, at 8:58 PM, Eric Norris <norrislawfirm2 at gmail.com> wrote:
>>>> 
>>>> Congratulations, Mike!  Please let us ALL know how it goes, as we of the K2 clan learn something with every post.
>>>>
>>>> 73 Eric WD6DBM
>>>>
>>>>> On Sun, Jun 28, 2020, 2:12 PM Mike Kopacki <mikekopacki at gmail.com <mailto:mikekopacki at gmail.com>> wrote:
>>>>     Well, that gives me something to do!  I’ll let you know how it goes.
>>>>
>>>>     Thanks,
>>>>     Mike NJ2OM
>>>>
>>>>     > On Jun 28, 2020, at 4:41 PM, Don Wilhelm
>>>>     <donwilh at embarqmail.com <mailto:donwilh at embarqmail.com>> wrote:
>>>>     >
>>>>     > Mike,
>>>>     >
>>>>     > Congratulations on finishing the K2/100.
>>>>     >
>>>>     > On the power output variation, that is not normal.
>>>>     > First check the voltage delivered to the K2 while in transmit.
>>>>     > You should do that by tapping DISPLAY and scrolling to the
>>>>     voltage display.  Your power source should provide at least 13.8
>>>>     volts, but higher (up to 15 volts) is better.  If the voltage
>>>>     shown by the K2 display during transmit is less than 12.6, make
>>>>     certain all power cable connections are tight.
>>>>     >
>>>>     > If the power supply voltage is not the problem, then remove the
>>>>     KPA100 from the base K2 and realign the bandpass filters.
>>>>     Connect a dummy load to the base K2 BNC ANT jack.  After that,
>>>>     check the maximum power from the base K2 - you should have at
>>>>     least 10 watts on each band.  Record the power for each band.
>>>>     >
>>>>     > Using a dummy load takes away any question about your
>>>>     antennas.  Always check into a dummy load - with an in-line
>>>>     wattmeter if necessary.
>>>>     >
>>>>     > The other possibility is that you have a problem in the Low
>>>>     Pass Filter in the KPA100.  To check for that, re-install the
>>>>     KPA100, but power the base K2 from the coaxial power jack (no
>>>>     power to the KPA100 - connect the dummy load to the SO2339 jack
>>>>     on the KPA100.
>>>>     > Again check the maximum power on each band from the base K2.
>>>>     It should be no more than 5% less than you found with the base K2
>>>>     only.
>>>>     > If there is a substantial difference in power, then check the
>>>>     KPA100 Low Pass Filter - particularly checking the number of
>>>>     turns on the toroids.
>>>>     >
>>>>     > 73,
>>>>     > Don W3FPR
>>>>     >
>>>>     >
>>>>     >> On 6/28/2020 4:04 PM, NJMike wrote:
>>>>     >> I did notice a variation on the power output on different bands:
>>>>     >> 80m - 100w
>>>>     >> 40m - 100w
>>>>     >> 20m - 80w
>>>>     >> 15m - 50w
>>>>     >> 10m - 30w
>>>>     >> SWR was never above 1.3-1.
>>>>     >> Does that sound normal?
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