The basic K2 power ouput indication is very accurate when operating into a 50 ohm non-reactive load. If it is driving anything other than that load, the indication will be inaccurate - he basic K2 does not have a wattmeter, t does have an RF Probe type detector which reports the RF Voltage to the microprocessor and the 'power' is computed based on the assumption that the load is 50 ohms.
If the KAT2, KAT100 or KPA100 is intalled, the RF Probe type detector is not used, but the real wattmeter in these options is used instead (the firmware knows which to use with no user input), and the power readings on the K2 will be asaccurate as your calibration allowed. Be aware that wattmeters are notorious for inaccuracies, many staqte their accuracy based on a percentage of full scale - even the Bird does this, so with a recently calibrated Bird with a 100 watt slug, the error can be as great as 5 watts anywhere on the scale. How many hams have properly calibrated wattmeters? Youn can actually calibrate your wattmeter with the RF Probe in the basic K2 - all it takes is a known non-reactive 50 ohm load. I use 1% precision thick film power resistors, so I know my dummy loads are good to 50 MHz or more, and with these loads, I know the base K2 power indication to be accurate. If you have the basic K2, the power control circuits will adjust the power to make the RF voltage at the power detector probe equal to that required to produce the requested power into a 50 ohm load -- but if the load is different than 50 ohms (as it will be with a 1.2 SWR), then the power indication will not be correct - tosay how far off it will be requires knowledge of the resistive and reactive components of the 1.2 SWR (all 1.2 SWRs are not equal, the range of possibilities form a circle on the Smith Chart). 73, Don W3FPR -----Original Message----- My K2 and my watt meter do not agree. When I set the K2 power output at 5 watts I get almost 10 according to the external watt meter. Setting K2 power output at about 12 watts gives something between 15 and 20 out on the external meter. At settings above about 13 watts on the K2 knob, I get the high current warning. This is all driving a 1.2 : 1 or lower SWR, btw. It leads me to believe the K2's power output is fine but it's ability to measure and report it is off. How accurate is the power output control knob supposed to be? I don't recall doing any calibration steps or alignment steps that affect that part of the rig. I have not (yet) measured voltage into a 50 ohm dummy load but am seriously considering dragging the rig, PS, dummy load & cables into work to have access to a scope. - Keith KD1E - - K2 5411 - -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.394 / Virus Database: 268.7.0/346 - Release Date: 5/23/2006 _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
