[time-nuts] 9390 GPS RX

Ed Palmer ed_palmer at sasktel.net
Wed May 29 13:31:17 EDT 2013

On 5/29/2013 9:58 AM, Mark C. Stephens wrote:
> Uh, well. No one told me about the heatsink thing :)

Section 2 in the manual talks about mounting and heatsinking.  You mean 
you didn't read the flippin' manual??? ;)  Anyway, it's good that you 
were able to get it on frequency.

> I am using a HP5370B.
> I am comparing to my best GPSDO.
> For instance my 5x Z3805A's get down to the low -12's after 1 hour.

Remember what these measurements mean.  Result = sqrt(<measurement 
system>^2 + DUT^2 + Reference^2).  Your measurement system and reference 
have to be significantly better than the DUT or they will affect the 
result.  The 5370B should be low enough to be ignored at these Tau 
values.  Your Z3805A should be okay, I think, but not by much.  My 
Z3801A happens to have a 'disciplining hump' that peaks at around 1000 
sec. and was affecting the measurement at 800 sec.  I was also using a 

> 4.7e-11 at 1 hour 12 minutes.

Yeah, that's high considering that the monthly drift is supposed to be 
less than that!  Let it soak for a month and see what happens.

> Do you think the FRK is ready to go back in the 9390 :)
> I hope so, I like that 9390 and I want it in my rack :)

Yes, I think so.  Like I said, see what monitoring capability the 9390 
has.  I suspect that the FRK will improve over the next while. Only time 
will tell how much.

Congratulations!  It looks like your FRK is alive!  After a little time 
to work out the last few kinks it should be in good shape. (Knock on 
wood!)  :)


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