[time-nuts] Question about an HP5370B TIC

[Hal Murray]

> If I put the 5370B in the +/-TI mode I expected to see both + and -  small
> time differences when the two signals are closely aligned - and  mainly I
> do.  Typically the difference is + or - a usec or less.  Occasionally
> however the 5370B displays very near to a +1 or -1 second  (999.999 xxx ms
> or -1.000 000 xxx s for example) reading.  Needless to  say this plays havoc
> with trying to measure a mean value of the  alignment.  The 5370B is clearly
> measuring the "outside" between the  pulse pair when I want it measure the
> "inside" (or short time interval)  between the pulse pair.

How are you collecting the data?  If each sample gets to a PC, you can fix it 
up in software.
    If X > 0.5: X = X -1.0
    If X < -0.5: X = X+1.0
One disadvantage of that is that those samples eat 2 pairs of pulses so you 
are only getting half as as many samples per hour.

I like John's suggestion of triggering one side off the other edge of the 
pulse.

Is the pulse from the OCXO supposed to be synchronized with the GPS second?  
If not, just zap the counter to move the pulse around within the one second 
window.  (I'm thinking of shorting out one of the counter bits with a 
screwdriver or clip lead for a fraction of a second.)

My first thought was to insert a delay line, but that will take 1000 feet of 
coax.  Maybe more.  I don't have that handy.  Frys says $80 or $90 for 500 
feet.   I'm too cheap to buy it just for one test like this.  (But I might 
use this as an excuse if I see some at a good price.)


-- 
These are my opinions, not necessarily my employer's.  I hate spam.