[Elecraft] K3 High Current Warning on 10m

[Malcolm]

"Bryan, ZL1NI" <akiwiham at gmail.com>
Wrote
Subject: [Elecraft] K3 High Current Warning on 10m
To: elecraft at mailman.qth.net
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On 28.010 while in Tune a high current warning came up then a 15A fuse 
went in my Astron power supply. My MFJ-259 shows SWR less than 1.5 at 
this frequency. The antenna is a new SmallIR.
I have since operated my FT-897 on the same antenna and frequency. I can 
key down at 100W as often as I like and for as long as I like and 
nothing bad happens. Rig indicates a low and stable SWR putting out 100W.
This seems to suggest something related to the K3. Has anyone else 
experienced this?



Hi Bryan,

This is caused by the supply voltage at the K3 being below 13.8 Volts because of the 
current being drawn to provide the RF power out on the higher frequencies. The K3 will 
draw a higher current to try and put out the higher power thus compounding the problem.
The voltage drop can be due to using wire that is too thin,  oxidised connectors and that 
includes the fuse connectors or a power supply with insufficient capacity or poor regulation.

I would try measuring the voltages when keying say 50 Watts. Measuring the drop along 
each wire of the cable should show where the problem lies.

Regards

Malcolm
G0MIC