Antenna mask of zero degrees is actually NOT good. You get satellites going in and out of your antenna's view too often (because satellite can pop in and out of horizon, and other obstructions), cause switches in satellite used, and that contribute to fluctuations. 10 to 20 degree, in most cases, will give you better results. I'd suggest seeing what it is set to and adjust accordingly. "Auto" anything will assume a lot of things, and what it arrives isn't always the best.
Also, what T-bolt outputs and LH displays isn't an actual measurement of the output. It's a computed figure. I don't actually look at it... as long as it's locked, I'm pretty happy. By the way... I have a lot of GPSDO in my lab. Short term fluctuation of output vary quiet a bit. That is quite normal. It is designed to give you a good average over time. (hours to days) --------------------------------------- (Mr.) Taka Kamiya KB4EMF / ex JF2DKG On Friday, March 20, 2020, 5:51:27 PM EDT, Frank O'Donnell <t...@inkbox.net> wrote: I hope you all don't mind a novice-level question, but I'd be interested in any feedback on what I'm seeing with the accuracy of the 10 MHz signal out on my Trimble Thunderbolt. I bought the Thunderbolt last year used on eBay, and it appears to be of about 2001 vintage. Most recently it's been running continuously for about 2 1/2 months, attached to a roof-mounted Lucent PCTEL 26db twist antenna with a clear view of the sky, with the receiver located in a room with a relatively stable temperature. Lady Heather and Thunderbolt Monitor both appear to report it to be well settled-in. My main use of the Thunderbolt is to supply a 10 MHz reference signal to an HP3586B and HP3336B for frequency measurement purposes. At the beginning of this month I remember typically seeing about 20 ppt accuracy for the 10 MHz reference as reported in Heather. I then used Heather commands to initiate an autoset of oscillator parameters (set antenna elevation mask angle to 0 with FE keyboard command and set signal level mask to 1 with FL command in order to allow collection of signal level data across full sky; clear signal level history with CM keyboard command; let run at least 6-12 hours to build up new satellite signal level map; issue “&a” autotune command, allow time to complete). Now I seem to be seeing about 60 ppt accuracy on average. For my purposes, these differences are probably academic -- if I'm doing my math right, 60 ppt in a 10 MHz signal is 0.0006 Hz, far down in the noise of frequency variation due to Doppler etc. Still, I guess I've drunk enough of the Koolaid to wonder about the accuracy level and any ways to improve it. So, some questions. Is it possible that the increase in the error seen could be due to the oscillator parameter autoset sequence that I ran? If so, is there a way to remedy this? What would be typical accuracy for the 10 MHz reference on a Thunderbolt? Is there anything else I can do with the Thunderbolt itself to increase the accuracy? If I want to consider an alternative to the Thunderbolt that might offer better accuracy, is there a logical next step? Thanks for any suggestions, Frank _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.