Ed... Very good data!
I am curious about one part of the warmup process. At around 7 minutes, the power jumps up radically, which you attribute to the outer oven kicking in. It has often been stated on this list that the outer oven was intended for use during really cold starts, which I would expect should cause it to kick on almost immediately during a very cold start. I am assuming your start was from room temperature. For a room temp start, I wouldn't expect it to kick on at all if it's purpose was as reported. Or do I have the oven functions reversed? Tom Holmes, N8ZM -----Original Message----- From: ed breya <[email protected]> Sent: Friday, January 28, 2022 9:50 PM To: [email protected] Subject: [time-nuts] Re: HP Z3801A project update I've been doing some more cold start testing, and thought I'd share this info, for any Z3801A owners who may be curious about the behavior. Some aspects are probably well known since long ago. I've seen it all since first starting work on this some 10-12 years ago, so I know approximately what it does. Now I have been able to make some more convenient observations. The setup is simply measuring the external DC input current and voltage while the process goes, to estimate the input power needed, roughly how much, and when. Only the input P is noted. The total gets used up in running the Z3801A, the other circuits, and conversion losses. Almost all the changes in power are due to the Z3801A going through its cold startup process. Here's a summary from a run I did this afternoon. T=0, start, 33 W The running supplies for everything, and the internal oven of the OCXO are turned on first. When the oven is approaching being warmed up enough, the P gradually drops to about 25 W, at about T+7 min. It then rather suddenly jumps to somewhere around 50 W as the outer oven is turned on, then fairly quickly down to 45 W, then gradually declines. The GPS lock indicator came on at about T+10 min, not coincident with any particular oven condition. The power continues to drop off very gradually (there's a lot of mass to heat up), until reaching nearly steady state around T+50 min, at about 25 W. So, figure it takes about ten minutes to achieve lock (this particular setup), but about an hour for everything to fully warm up. Ed _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
