I wanted to characterize the start-up and steady state power requirements so that I could design a simple power supply to run the Z3801A.
Data was recorded by using the PICDAS. A data acquisition system designed by Steve Hageman. It is described in an ARRL publication, QEX in January 2001 on p 52. The device cannot measure current directly. A current sampling resistor was added into the power supply positive leg. Data resolution was 10mA. At 56.6 vdc this means a resolution of 0.6watts (0.566).
The user manual for the z3801a lists the power requirement as “<25watts (nominal)”. Clearly, that is the steady state power requirement. I allowed the unit to cool to ambient ~60F for three days before startup. I polled the PICDAS approximately every 12.5 seconds. If the computer had other things going on, there might have been a delay here or there, but in 90 minutes it had collected 430 data points. The longest time between samples was 15 seconds.
It appears as if the unit powers up with only one of the two ovens energized (inner). After diagnostics for about seven minutes, it turns on the second, outer oven. Power consumption hits a peak of 39watts. As the oven comes up to temperature, the power consumed is reduced. By 36 minutes or so, the unit is back at the original power consumption. At just over one hour, it has achieved steady state. Likely, it would be longer to steady state if the ambient temp were lower.