[Elecraft] K2 K2/100 post FD review

Tue Jun 30 17:32:38 EDT 2020

Don...

The power supply is an MFJ 13.8V/25A switching power supply. It measures 13.63V at the terminals. 

The K2 shows 13.1V in receive mode. 

During transmit on all bands, the K2 shows 11.3-11.9V, depending on the band. 

All the power connections appear to be tight. 

Thanks,
Mike NJ2OM 

> On Jun 29, 2020, at 12:45 PM, Don Wilhelm <donwilh at embarqmail.com> wrote:
> 
> 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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> 