[time-nuts] FE-5680A GPS discipline board on sale now

[Nick Sayer]

This is a mash-up of my breakout board and GPSDO. You give it 30+W 18-24 VDC in (hack up a surplus laptop power supply) and it supplies up to 2A @ 15 VDC and 500 mA @ 5 VDC. In my testing I see around 25 mV p-p of ripple on the 15V rail. The 5V rail is a bit noisier at around 35 mV. Functionally, the discipline system is the same as the latest OH300 units - it has the phase discriminator that Jim Harman recommended, but now there’s a JFET that acts to make the phase ramp more linear (useful if you want to gather stats). The firmware has 4 modes of operation - an initial FLL, followed by a PLL with TC 100s, 1/2 hr and 2 hours. Once it’s in the 2 hour mode, the EFC value often goes for hours without changing (I’m throwing away the bottom two bits of EFC resolution).

It has a mini-DIN-4 diagnostic jack that has a buffered GPS PPS output and two TTL serial streams (log and NMEA), an SMA antenna jack (the module has an internal antenna, but an external one is recommended), a 2.1mm barrel connector for power and two JST jacks with independently buffered 5V square wave outputs. The board is the same width as the 5680A. It comes with rubber feet so it can rest on the table next to the oscillator, or you can remove them and mount it on 4 grounded screw holes in the corners. The three LEDs have light pipes to make them stick out from the edge of the board.

If you’ve got a 5680A and your biggest complaint about it is that it’s not actually *accurate* by itself, then this is a good solution.

http://www.tindie.com/products/nsayer/fe-5680a-gps-discipline-module/