[time-nuts] Build a 3 hat timestanp counter

[hans-georg at lehnard.de]

Hi, 

my Name is Hans-Georg Lehnard from Germany and I'm new here, worked as a
developer for hardware then for software and last as a system developer.
Now I'm retired and I can play with hardware again ;-). 

I have: 

4 x 20MHz Rubium (TEMEX MCFRS-1),
2 x 10MHz HP10811-60111
1 x Samsung UCCM GPSDO
1 x FA2 counter.
lots of OCXO 

and try to build a house standard that I can trust and qualify my
oscillators.
Reproducible measurements with the FA2 in 10s precision mode I trust to
10E-11. 
The short-term stability of the HP oscillators cannot be measured with
it, or both are defective.
The FA2 is not suitable for short-term measurements of 0.01 ... 1s. 

For measurements against a reference frequency, the stability of the
reference must be 5 to 10 times better than the measured frequency, and
I don't have that. Now there are 2 options DMTD mixer or 3-hat
measurements. 
Because I'm a digital person I chose the 3-hat method. 

The idea is now to divide the 3 measuring frequencies (20 or 10 MHz)
down to 100Khz and to measure the phases with a TDC against the next
reference edge. Average the measurement results until I am down to 0.001
... 1 s. That should improve the 100ps resolution of a TDC7200 far
enough and can also be output via RS232. 

Are my thoughts correct and could it work ? 

Hans-Georg