Posted by
dave.wilburn on
Jan 14, 2008; 9:46pm
URL: http://elecraft.85.s1.nabble.com/K2-100-Power-investigation-tp458672p458677.html
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
>>
>>
>>
>
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