The K3 SSB + CW Power Overshoot behavior has been passed up the Elecraft Tech/Engineering chain. I expect it may take them some time to get to it, so in the meantime it would be useful for those interested to conduct the test below to determine if the behavior is unique to my K3 or more wide spread. My primary concern is operating with the K3 driving an amplifier (KPA 500 in my case). It is often the case that the overshoot is so high that the KPA faults on the first key press when power is set for 500 watts and in SSB +CW mode. __________________________________________________________________________________ Following is a repeatable test that exhibits the overshoot and power adjust instability problem we have been discussing. Setup: 1, Output terminated in dummy load (ANT 1) 2. Config: CW WGHT -- [1] SSB +CW 3. S Meter Peak -- ON 4. Meter Mode -- SWR/RF (to observe output power) 5. Set Power 50 watts (initial setting) 6. Select any band Operation: 1. Select CW mode; VOX on Press key and hold. Note that power ramps up to the set 50 watt value Adjust power up or down; note that the power change is smooth with no jumps or overshoots Press key on/off/on .... -- power always returns to set value Release key and set power to 50 watts 2. Change to SSB mode (upper or lower) Press key and hold while observing watt meter -- note that power overshoots the 50 watt level and then drops to 50 watts. Adjust power up. Note that the power jumps high then returns to set value.
Adjust power down. Note that the power jumps high, than returns to set value. (note that whether the power is adjusted higher or lower, the output power jumps higher, then reduces to the set value). Also note that the power supply current jumps (overshoots high) coincident with each power adjustment. Release key, then press again and hold. Note that the power does not overshoot the set value. Release and hold any number of times and power continues to be stable at set value. Changing now to CW mode with VOX and power is stable. Changing back to SSB +CW and power is unstable and with overshoot with first key press. This phenomenon occurs in both HP and LP modes. This phenomenon is apparent when the K3 is initially turned on from a cold start, but gets progressively more pronounced after about 10 minutes of on time in quiescent state (no RF out). PA Temp at this time is 25C. As requested, fan is set to level 1. Discussion: It is my understanding from old Reflector mail posts that the SSB +CW mode is implemented such that when key is pressed, the K3 changes dynamically from SSB to CW mode. It appears that the CW ALC function is not in play until some time delay after key press, at which time the CW output settles at the set power level. This time delay would appear to be at the root of the problem. When the power is adjusted, it would appear the ALC loop opens up and then re-engages when adjustment stops. The fact that the phenomenon changes in magnitude as the K3 warms up, may simply be a function of linear stages within the ALC loop changing gain with temperature. The above test sequence is easy to apply and as such would be very curious to see if the phenomenon occurs on any of the Elecraft bench test K3's. ______________________________________________________________________________________ Thanks and 73, Dan AC6DM ______________________________________________________________ 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
