[time-nuts] Measuring frequency difference

[Raj]

I noticed the same John. I fired up the TBolt and it was not working fine till 
I set my location and height above sea level. Our city is about 928M ASL.

I must again check with a newer GPS for better coordinate accuracy.
Initially only two SV's lit green, after I set the co-ordinates then all are
green. Now the 10MHz is jumping between <0.1 >0.00 ppb. comparing
with a a FE5680.

>I started out using an oscilloscope and comparing OCXOs to my Z3801 GPSDO.
>Later I used it to compare an LPRO 101 to the Z3801 and finally, a TBOLT. I
>later acquired a Racal 1992 which makes things a little easier but no more
>accurate in my opinion. If you are looking at frequency difference or
>frequency drift, and not stability, either of these methods and a stopwatch
>will get pretty good results. It took me a couple of days to get an LPRO
>adjusted so that I saw one cycle slip every few hours. It takes patience.
>The thing that surprised me was how much a TBOLT moved around compared to my
>Z3801. Though it stayed within one cycle because it was "phase locked", it
>jumped around a good bit while the LPRO just slowly slipped in one direction
>or the other.

-- 
Raj, VU2ZAP
Bangalore, India.