I believe most every electrical device and piece of equipment will have some type efficiency curve for power in and power out. A motor sitting at idle is using power, but doing almost no real work. However, at no load it is still using watts. Typically a motor has the best efficiency at around 75% load or so.
I am sure an amplifier or any electronic device is similar to a motor or transformer. There are always "no load losses", that you need to have regardless of the load on the device or output of the device. Also, I am not sure you are looking at the entire picture with your numbers. I see that you are multiplying the DC amperes x DC volts. In reality, the power supply has to make that DC power, and it also has some electrical power loss. You should really use a power meter on the 240V feed from your panel to get the exact input power required for the KPA-1500. That is why Elecraft recommends a 20A feeder at nominal 240V input. The range of the power supply is 195V to 250V. At maximum power output of the amp there will be less amperes used at 250V than 195V but it will require the same input power. There is a maximum power dissipation hard fault @ 2050 watts. So, that would say if you are dissipating 2050 watts, and putting out 1500 watts RF, that would require 3550 watts of input power. At 240V that is about 15 amps and at 195V that is over 18 amps. You don't want to run it that high or at that efficiency. You need to make some changes in your setup to keep below that level. The calculations are even worse for the "efficiency" using the power used on the 240V side, but that is what you are really paying for in your monthly electric bill. What you did probably is close enough for discussion and Elecraft metering reflects those numbers, but it is worth noting there are many factors that enter into an "efficiency" calculation. Loading the amp into a dummy load gives you one set of data. However, the better your antenna matches at each frequency without needing the tuner, the less heat the tuner will create doing it's job to match to 50 ohms, so the amp can put out maximum power. Of course, if your antenna has a high SWR, because of it's electrical design, you are just making heat somewhere, and not putting your power used to good RF output production for getting your station heard on the airwaves. Bill, K8ZCT -- Sent from: http://elecraft.365791.n2.nabble.com/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
