[time-nuts] Measuring 10 MHz accurately.

[Martyn Smith]

Hi,

Two questions for all of you today.

1st Question

I can measure 10 MHz frequency to an accuracy of about 2 parts in 10E-12 in 
a one second gate time.

I use a SR620 time interval counter and make a timeAB measurement.

I make two measurements of phase (between my UUT and my reference)  and then 
calculate the frequency.

I have some nice software that controls the SR620 and does all the math.

I'm sure most of you understand my measurement technique, since it's as old 
as the hills.

Does anyone have a good application note explain this standard procedure? 
I'm trying to explain it to a friend, and can't find a nice application note 
with some diagrams, formulas etc.  I know HP did one and Standard did as 
well, but can't find any quickly.

2nd Question.

I really need to measure 10 MHz to an accuracy of 1 part in 10E-13 / second 
(ignoring the accuracy of my workshop standard).  I've tried multiplying the 
10 MHz to the GHz frequencies, but never manage to improve on the technique 
I mention in my first question.

Any ideas for a relatively cheap way of doing this.  I actually represent a 
company that can measure to parts in 10E-15 in one second, but their boxes 
costs $50k.

Best Regards

Martyn