[time-nuts] Different Survey Results

[Peter Krengel]

To John WA4WDL:

The coordinates out of my current (fixed) position  calculated by
the SirF GPS and the tbold during a 48h survey are different.
On a map this differences makes up a shift of up to 100m around
my true qth. With other words if I would (and could) use the tbold 
as a mobile GPS I would come off road at once ;)


To ws:

Thanks for the interesting answer and tips for modifying factory settings.

My tbold works in a good stable (temperature) environment. I tried out
to put it in a temp-isolated box but Osc temperature went up to about 50°C
(not too hot?).

Secondly I tried it without a box at normal 20°C room temperature (varying a little bit) and it showed OSC 41.75°C. 

What is the better choice?

It also got fine antenna conditions (mostly 8 sats are recognized having
signals between 38 and 48dBc) by using a roof top ceramic chip antenna (it has a inner preamp)  followed by a 20dB wideband amp and about 20m
coax. As I am located on a hill top it "sees" a 360° free sky down to 0° elevation.

I got the following results using factory settings after cold start and 10 hours running with my true (are they really my true coords?) qth coordinates saved after self-survey:

OSC ADEV
1        tau  2.7E-09
10000 tau  7.0E-13

My intension (of cause..) is to get the best out of the tbold in short and
long term stability.

The tbold isnt modified in any way running the original oscillator.

What do you think ?

------------------------------------

To Mark:

I too got a LPRO rubidium but it I'm not very satisfied because of the need of long time warm up after power fail and the need of a heat sink.

In addition the tube wont last for ever and is used for 10(?) years...

Anyway I would like to compare both tbold and Lpro if the tbold is
setup best as possible.


Thanks and regards
Peter  DG4EK