[time-nuts] any HP 5370B Available or other TIC

[Bruce Griffiths]

Javier Herrero wrote:
> El 18/08/2011 08:37, Bruce Griffiths escribió:
>> DMTD or dual mixer time difference.
>> An all digital version (DDMTD like that used in CERN's White Rabbit) 
>> is also possible
>> 3 (and M) input versions are also feasible.
>> Either an FPGA or a CPD plus a microprocessor are required to ensure 
>> low cost.
>>
> I've lying around one of these little things: 
> http://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=139&No=593 
> (that really I purchased only for amusement along with a bigger and 
> quite more expensive FPGA board). It lacks I/Fs except GPIOs (it only 
> has an USB that really are more intended for JTAG functionalities than 
> for other things), but seems a nice unexpensive core for a DDMTD. It 
> could be a fun project :) Anyone would like to join? ;)
>
> Regards,
>
> Javier
Javier

I've already done some preliminary test using 74HC164s as mixers to see 
what the limits are.
With 5.000055MHz clock and 5MHz data inputs the noise floor was around 
1E-11/Tau.
However better estimates of the beat frequency transitions than that 
achievable using a 5370A to measure the relative delay between the mixer 
output transitions are necessary.
CERN make all the required DDMTD  VHDL code freely available.

One potential advantage is that the data input frequency could be any 
harmonic of 5MHz with a 5.000055MHz shift register clock.
Thus one could compare 10MHz and 5MHz standards directly using a DDMTD.

Bruce