[Elecraft] Question about 120 volts vs. 240 volts house supply to KPA 500

[Andy Durbin]

"No need to do that -- we can read DC voltage inside the amp on the built-in panel meter, and that's what matters."

The DC meter voltage difference between RX and TX depends on the stability of the AC feed voltage and the drop inside the KPA500.  The drop inside the KPA500 depends strongly on output power, band, and load matching.  Measuring only the DC voltage provides no direct information on the quality of the AC feed.

I suggest that to understand the full picture on would need both the DC drop inside the KPA500, the PA current,  the AC voltage drop at the nearest possible measurement point to the KPA500, and the AC current draw.

I have my KPA500 permanently connected to a KillaWatt and my KPA500 60 V  supply voltage and current are continuusly logged while transmitting and for 20 seconds after TX stops so I have lots of data to look at.  My conclusion was the the biggest external factor influencing my nominal 60 V supply voltage was the load on my street transformer.  That variation of service voltage with load would not be improved by changing from 120 to 240 service because the load that pulls that transformer output down is not just my house it's all the other houses in the street that are on the same transformer.

I try to minimize my 60 V sag by getting the best possible load match.  I have no plans to change to a 240 V feed even though my service panel is probably less than 15 feet from my KPA500.

73,
Andy, k3wyc