[Elecraft] K2: KPA100 fan issue + current question

[Jim KO5V]

Thanks again, Don.

It's good to know that the variation in current isn't a problem. I was also a bit surprised with the 12M and 20M measurements. 

I think I will do a complete realignment of the K2, and set up the wattmeter on the KPA when I get the LP100 back. Meanwhile, I'll try a few QSOs at 50W or so and see what happens.

73, Jim KO5V


-----Original Message-----
>From: Don Wilhelm <donwilh at embarqmail.com>
>Sent: Nov 9, 2018 5:15 PM
>To: Jim KO5V <ko5v at earthlink.net>, Bob McGraw K4TAX <rmcgraw at blomand.net>, Elecraft List <elecraft at mailman.qth.net>
>Subject: Re: [Elecraft] K2: KPA100 fan issue + current question
>
>Jim,
>
>That is normal.  The Transmit RF Gain varies from band to band, and that 
>will cause the current draw to vary.  I am surprised that 12M is so low, 
>it is normally on a par with 10 meters.
>
>Part of the RF Gain variation is in the base K2 and some more of it is 
>in the KPA100.
>
>Remember that those are steady state current draws.  The dynamic current 
>such as with SSB operation may peak at greater than what you measured.
>
>Yes, use the LP-100 for calibrating the KPA100 wattmeter.  Since the 
>LP-100 has NIST traceable calibration, I would believe it over the 
>readings on a calibrated BIRD.
>
>73,
>Don W3FPR
>
>On 11/9/2018 5:56 PM, Jim KO5V wrote:
>> Don and Bob,
>>
>> The K2 and amp are both powered from the amp's supply.
>>
>> I used a known good DVM to measure the voltage across R7, and it agrees with old Beckman. I now think my old kit-built Ten Tec power meter may be badly out of calibration. I have a dead LP-100 that is on its way back to Larry for upgrade and calibration, so I'll just wait until it is back to finish calibrating the KPA's power setting.
>>
>> Here are what I measured and calculated at the approximate center of each band, in cw, when the K2's LCD read 100W:
>>
>> 10M: .067V, 13.4A
>> 12M: .049V, 9.8A
>> 15M: .064V, 12.8A
>> 17M: .065V, 13A
>> 20M: .048V, 9.6A
>> 30M: .056V, 11.2A
>> 40M: .052V, 10.4A
>> 60M: .056V, 11.2A
>> 80M: .054V, 10.8A
>>
>> The current seems to vary significantly between bands, but maybe that's normal?
>>
>>
>