Leigh, I agree with Chuck. I have both an FE-5650A and an FE-5680A. With the former I was concerned about the heat, and so ran it only for short periods, until I understood what was going on. I had the impression from the data sheet that there were different heatsink options for different temperature ranges, and I now believe this led me astray.
With the FE-5680A I had the opportunity to study things in more detail. There is no temperature range specification that I could find, and no particular advice in the manual regarding installation. I ran the unit from regulated 15V DC, and monitored the supply current. With no extra cooling, the steady state current was about 700mA. With air blown over it, the current increased. With the unit placed in a poly bag, the current decreased to about 650mA. By the way, the current also decreased when operated from 17V DC. This tells me that the whole structure is part of the thermal package, and we should not attempt to force down the case temperature just because the unit runs hot. My experience with high performance OCXOs tells me that the thermal environment is carefully designed, and part of the calibration process - if you modify this environment (by cooling or extra insulation) you modify the thermal environment, and are at risk of modifying the performance. I'd leave well alone, and run the unit in an open, breeze-free environment. 73, Murray ZL1BPU _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.