[Elecraft] K2/100 - Power investigation

[David Wilburn]

Yea, not having a good day.  Switching dummie loads and powers and 
such.  Smoked the DL1, small dummy load, large power.  Hobbies are 
supposed to be fun....right?  ;)


Dave Wilburn
K4DGW
K2/100 - S/N 5982


Don Wilhelm wrote:
> David,
> 
> You are chasing your tail since you are trying to use all those 
> wattmeters - they will all be different.
> You say that you are using a wattmeter between the KPA100 and the KAT100 
> - that in itself can lead to a variety of readings.  The only thing you 
> can really trust is a good dummy load.  The DL1 is good.
> 
> Because of the scaling done in the KPA100 for the output of the 
> wattmeter to the K2, you can calibrate it at low power.  Disconnect the 
> power cable from the KPA100 and power only the base K2.  Now, you can 
> use your DL1 dummy load and do the calibration at 10 watts (the power 
> control is a lot easier to use with no PS connected to the KPA100).  Be 
> certain your KPA100 wattmeter is balanced first (do that into a good 50 
> ohm dummy load or it will not be correct - use your DL1).   Then set the 
> KPA100 forward power pot so the K2 display matches the power calculated 
> from the DL1/DMM reading.  You may have to make several trials to 
> average things out, but once calibrated that way, your KPA100 wattmeter 
> will have greater accuracy than the run of the mill wattmeters - and it 
> will be accurate on both the low and high power scales.
> 
> If you do it right, you can judge the accuracy of those external 
> wattmeters by comparing them to your KPA100.
> 
> You can expect some variation from band to band because the diodes are 
> not entirely linear with frequency.  Pick one band and stick with it 
> while doing the calibration.  Attempting to calibrate on several bands 
> is an exercise in frustration.  I like to use 40 or 30 meters, but if 
> your operation is mostly on 20 meters, then that may be a better choice 
> for you.
> 
> If you are attempting to compare wattmeters  with a live antenna, 
> remember that common mode current on the feedline can also have some 
> influence, and the amount of influence may be vastly different from one 
> meter to another - as I said, the only thing you can trust during these 
> calibrations is a known dummy load.
> 
> 73,
> Don W3FPR
> 
> David Wilburn wrote:
>> Ok, I got all kinds of numbers off of the DL1.  The Bird seems a touch 
>> low, showing 80 - 100w across all bands.  Every time I measure it a 
>> different way, I get different numbers.  Very frustrating.  The W1 
>> quit after about 5 min.  The MFJ meter gives one reading, the Bird 
>> another, using the DL1 and doing a calculation, goes crazy on 10&12m 
>> but more stable, and once again different on others.  Friend is going 
>> to loan me his Bird, think it is a 4309, and we will see what it 
>> shows.  I have put the Bird between the K2 & the KAT100, and 
>> transmitted and then ID'ed, and got the 80 - 100w.  Am I chasing my tail?
>>
>>
>> Dave Wilburn
>> K4DGW
>> K2/100 - S/N 5982
>>
>>
>>
>