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Re: KX3 Power Cable

Posted by hhoyt on Feb 07, 2018; 3:04pm
URL: http://elecraft.85.s1.nabble.com/KX3-Power-cable-tp7637906p7637963.html

Dave,

The vast majority of the voltage drop you see is not in the DC Power cable, it is in the anti-parallel polarity protection diode in the KX3 itself and all KX3 users see this drop regardless of what gauge cable you power the KX3 with.  A 1 M length of 18 gauge cable will drop less than 0.1 V at the maximum current of 2.5 A the KX3 can draw at 15 W.

Your internal voltage reading of 11.4 V is too low for the KX3 to allow operation over 5 W, and the problem is your power supply voltage is too low.  I suggest you use a power supply which delivers at least 13.8 V with a receive load of 0.2 A.  That will fix your transmit power issue, and it is the reason we designed the Kx33 Low-RFI power supply to output 14.2 V at a KX3 receive load of 0.2 A.  There are other advantages as well to this higher supply voltage such as higher power output with lower IMD in digital and SSB modes.

Cheers & 73,
Howie - WA4PSC
www.proaudioeng.com


>>I am using the standard power cable that is supplied with the KX3.  Using a
>>digital multi meter and the built in voltage monitoring capability of the
>>KX3, it looks like the supply voltage is dropped by 0.5 volts in the power
>>cord when transmitting with 5 watts

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