Re: [time-nuts] inexpensive fiber optic distribution

We've tinkered with SFP-to-SMA adapter boards like this: https://github.com/aewallin/SFP2SMA_2018.03 http://www.anderswallin.net/2018/04/500-mhz-sfp-board-v4/ although designed for 1 Gbit (1.25 GHz, or 800 ps 'bits') they work down to 10 MHz (and 5 MHz IIRC). With a decent interface-board and a sh

Re: [time-nuts] Distribution amplifier for 10MHz and 1 pps

Yo Bubba Dudes! Wrote: Gosh. This topic comes up at least once every 6 months. Adiligent search of the time-nuts database would turn up amazing things. . . Yep, it does and it always will for at least two reasons. One, we have new people joining the list.  Which is great. They're at the beginnin

[time-nuts] inexpensive fiber optic distribution

While researching this for a radio telescope, I found amazingly inexpensive (<$10) fiber optic transceivers for 1Gbps sorts of rates.. They take a standard singlemode duplex fiber and have a pinout suitable for plugging into a Cisco, etc. switch. Apparently, there's some internal programming w

Re: [time-nuts] Yet another GPSDO project.

Hi One nice thing about just getting the TICC from TAPR: https://www.tapr.org/kits_ticc.html Is that all of the glue and hook it up stuff has already been done and debugged. There’s also code on the attached MCU to take care of all sorts of odd stuff. John

Re: [time-nuts] Yet another GPSDO project.

Tobias, If your controller has a 10 bit ADC available, I would suggest using the TIC circuit in Lars's GPSDO. For a 10 MHz input, it needs only a 74HC390 divide by 10, a 74HC4046 phase detector, plus 1 diode, 1 capacitor, and 2 resistors to produce a 1 nsec resolution TIC. You get a fresh TIC valu

Re: [time-nuts] Yet another GPSDO project.

Hi Bob yes, this is exactly what I do currently. My microcontroller offers some 32 bit counters. I use the OCXO as clock for one of these and let the counter run all the time, it is never stopped. With every rising edge of the 1PPS signal, the counter value is copied into some register (input c

Re: [time-nuts] Yet another GPSDO project.

Thanks Achim :-) I actually have no idea what foam it is *exactly*, but I would call it Sagex, though, because it is somewhat similar. But it is mich lighter and quite hard, so it is not exactly Sagex, you are right! I used this name just because I lacked a better one. My GPS module indeed has b

Re: [time-nuts] Yet another GPSDO project.

Hi again Bob, I read some documentation about your TICC and tried to figure out how I could implement something similar in my GPSDO, but having only one channel. I ended up with this: https://hb9fsx.ch/wordpress/wp-content/uploads/2019/03/20190320_214120.jpg It works as follows. The GPS 1PPS i

Re: [time-nuts] Yet another GPSDO project.

Hi Bernd, awesome that you still remember this :-) sure, I believe you since my primary requirement was phase noise. This is because I'd like to use the OCXO as reference for my spectrum analyzer and also for my HP 8663 signal generator to do phase noise measurements - the signal generator can

Re: [time-nuts] Yet another GPSDO project.

Hi Tobias, Indeed the OCXO which you got from us (AXTAL) was an item from stock, which was not particularly designed for low ADEV. As it is from an older production lot, the aging may meanwhile be much lower than specified. If you want, you may ship your OCXO back to us. We will be glad to measur

Re: [time-nuts] Yet another GPSDO project.

Tobias Pluess writes: > By the way, this is the unit I built: > > https://hb9fsx.ch/wordpress/index.php/2018/11/14/my-own-gpsdo-part-i/ Nice build. Minor nit: Whatever foam you used to isolate your OCXO further is probably not SAGEX, but looks to be either cross-linked PE foam or (more likely) PU

Re: [time-nuts] Yet another GPSDO project.

Hi Indeed you want a digital “phase detector” of some sort. Your counter on the micro is a phase detector. If you clock it off of the OCXO and read it based on the PPS, what you get is phase. If you never arbitrarily reset the running counter, it reads phase forever and ever (no slips). If yo

Re: [time-nuts] Frequency Ensemble

Oops, units for TDEV are seconds, not nanoseconds! On Wed, 20 Mar 2019 at 7:41 pm, Michael Wouters wrote: > Hello Dan, > > > As promised here is a comparison of the ZED-F9P and NEO-M8T > sawtooth-corrected PPS. The PPS is measured against a 5071 with standard > tube. Three days of data were used

Re: [time-nuts] Frequency Ensemble

Hello Dan, As promised here is a comparison of the ZED-F9P and NEO-M8T sawtooth-corrected PPS. The PPS is measured against a 5071 with standard tube. Three days of data were used. The 5071 was measured against another 5071 and I divided the TDEV by sqrt(2). The 5071 data at shorter than 300s is li

Re: [time-nuts] Yet another GPSDO project.

Hi, no, I don't want the OCXO to closely follow the 1PPS - this would make no sense. Instead I thought the "right way" of doing it is perhaps: a) measure the phase difference between the GPS PPS and the PPS derived from the OCXO. b) put that phase difference into a loop filter. c) the loop filt