MY QO100 SETUP

SV1BDS George I am also building this next week.. just waiting for the module to arrive here..

SV1BDS George I will try to correct this with a lookup table

SV1BDS yes George I will do..waiting at the moment for the parts..

SV1BDS & DD0KP

what AD8302 module are you using?

the one made by Makis SV1AFN?

Claudio

SV1BDS Yes, your chip number is 1 higher than mine but I was not satisfied with the results. However, that also could have been caused by the 10 MHz TCXO (old Philips type) I used.

I now use the Ublox NEO-7M in normal PPS mode in conjunction with an OCXO and Arduino to provide a rock steady low phase noise / non-jitter 10 MHz reference signal.

SV1BDS  PA3FYM I was not satisfied with all the easy solutions too. I am using know a system with arduino, ocxo an 1pps which is described here: https://www.eevblog.com/forum/…o-and-1ns-resolution-tic/

Very clever and good working.

Yep, that one I am using: Lars GPSDO. Modified some of the code to investigate improvements.

PA3FYM Thats very interesting. Could you explain where you did improvements in the code or share your code?

- ADC7 is now sampling port

- speeded up ISR (int serv routine)

- ADC clk_div = 16 (instead of default 128)

- speeded up PWM DAC code

- changed PWM mode to 'phase correct' PWM and F_PWM = ca. 31 kHz (= F_CPU / 510)

- changed EEPROM write and read routines to Little Endian

- (tried to) added TC converging scheme

- experiment with EMA and DEMA (double exponential moving average)

- keyboard input is read once

What my GPSDO does now: It starts up with a low time constant (TC = 16) and when a lock is achieved the TC increases periodically and converges to the (from what I understood from the whole EEVblog-thread) optimal TC for the configuration.

The TC itself is also part of a seperate PLL in a sense it calculates the DEMA of the 'ns values' (most left column). The DEMA has to be within certain limits. When the DEMA falls 'out of lock' the TC is decreased.

PA3FYM That sounds great. Could you share your code or post it in the eevblog forum? I think readers of the lars gpdso forum are interested in this improvements, especially the auto mode for the TC setting. Lars himself passed away last year, so he can not do any changes.

I am a member of that forum and posted some in this specific thread. I first want to fiddle with it some more before I release the code. The Lars GPSDO is now a dedicated QO-100 reference and I moved my other reference back into the shack to feed the measuring equipment : -)