Thanks to all of you so far that made comments on the GPSDO plots; I'll handle this one first.
> Tom > > Both the Thunderbolt and Miller designs appear to measure at least 10x > better than the most optimistic expectations. Bruce, Interesting thought. What calculations did you use to set your expectations? The free OCXO in both those GPSDO are well within reason, no? And both GPSDO follow a fairly standard couple of ns over root tau line, yes? > One possibility is injection locking of the OCXO via its EFC due to > inadequate shielding or via its output due to its buffer amplifier > having inadequate isolation. To prevent, or at least detect, this effect I allow my 10 MHz house reference to drift off-frequency by quite a bit (last month it was 1.7e-12 off). That way there are no on-time or on-frequency sources near the test setup. > What cable types did you use to connect the GPSDO's and the reference > signal to the Allen deviation measurement instrument? For these tests I used a TSC 5120A; a 3 meter mil-spec RG58C cable to the UUT; the reference comes into the lab from another room over Andrew heliax FSJ1-50A. I get the same performance with and without 10 dB pads, and with or without RF isolators. Between the deliberate frequency offset, the cables, and the pads/isolators I'm pretty confident of the test setup. If you have additional ideas, let me know, and I'll give them a try. > Is there any way to measure the Allen deviation of the 10kHz GPS > receiver output, or at least verify that the 10KHz phase is jerked every > second. > The jerk may be done by adjusting the length of the 10kHz cycle just > before the second marker. Yeah, I will try to measure the 10 kHz directly for you. I was curious also, having never examined a Jupiter GPS in detail before. p.s. It's Allan, not Allen. /tvb _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
