[Elecraft] K3 voltage reading

[Don Wilhelm]

  Steve,

I don't think that is unusual.  The K3 display reads the voltage after 
the protective diode, so there you should consider a 0.3 volt drop due 
to the diode, that leaves 0.4 volts of drop from the power supply to the 
inside of the connector on the K3.  If I assume 17 amps current draw, 
that says the resistance is 0.023 ohms.  You have 10 feet of #12 
conductors (yes, one must count the return conductor too) for which the 
resistance is 0.016 ohms, and add a few extra milliohms for each 
connector - 2 at the power supply and 2 at the K3, so a 0.4 volt drop 
across the cable is not unreasonable at 17 amps current draw.

The conclusion is that you can reduce the drop by shortening the power 
cable - and make certain the connections at the power supply are tight.  
With some power supplies, the loose connections are on the inside - 
worthy of a check.

73,
Don W3FPR

On 11/17/2010 10:02 AM, Steve Ellington wrote:
> Can someone take a look at their voltage reading on their K3's DISP-V window and tell me what they get with key down, full power output into 50 ohms?
> My PS shows 13.7v at it's terminals and the K3's display indicates 13.1v. I'm just wondering if there is excessive voltage drop on the power leads. I'm using the factory cable. I'm not sure if the K3 is indicating the voltage at rig's connector or the voltage on the final amp. transistors.
>
> Steve N4LQ
>