[Elecraft] K3 Transmit current drain

[B Hunt]

Remember that at 12 watts and below the KPA3 is in bypass so the current 
will be lower relative to the output power.  Also the K3 configuration 
has something to do with it.  My K3/100 (SN 4113) is bare bones with no 
additional current drawing options.  Using the internal metering in the 
K3 and running into a 50 ohm dummy load, my comparable readings (plus 
supply voltage) are:

Receive = 0.77 A, 13.7 v
Transmit @ 1 w = 2 A, 13.6 v
Transmit @ 5 w = 2.8 A, 13.4 v
Transmit @ 8 w = 3.2 A, 13.3 v
Transmit @ 15 w = 7.8 A, 13.3 v  (KPA3 enabled)
Transmit @ 30 w = 10.3 A, 13.3 v
Transmit @ 100 w = 17 A, 12.9v

I'm using a linear Astron RS-35A power supply which doesn't seem very 
well regulated above 15 amps but the voltage as measured by the K3 
internal metering has all the cable and connector voltage drop in it.

Also you might want to make an independent check of the accuracy of the 
ammeter in the MFJ 4225 (if that is what you are using to measure the 
current).

HTH

73, Brian, K0DTJ

On 2/6/2012 6:14 PM, k6mgo wrote:
> I was playing around with my K3 and MFJ 4225 switching power supply, when I
> noticed a strange thing. As you increase the power output, the input current
> rises very quickly. Example:
> in Receive mode, the K3 was drawing 2 amps.
> In Transmit mode, CW, SK key down, at 1 watt out, it was drawing 4 amps
> 5 watts out, it was drawing 5 amps
> 8 watts out, it was drawing>6 amps
> 15 watts out, it jumped to 15 amps
> 30 watts out, it jumped to 20 amps
>
> Didn't want to increase the power anymore, but, this seems excessive to me,
> anyone else ever notice this?
>
> Would appreciate any comments on this matter,
>
> 73, Bill, k6mgo
>
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