[time-nuts] Different Survey Results

[Arnold Tibus]

Peter,

My TB is running continuously during months.
It draws about 7 W using the black PWR-supply proposed by Tom (TvB).
In the room at about 22 °C it does show 32.43 °C, I never passed 37 °C.
 So I would propose to net go beyond the 40 °C internal temp. reading. I
will manufacture a wooden box with thick walls to stabilize the temp.
Wood does of course not shield, but because the high thermal capacitance
together with its isolation (moderate)it should result in a
long thermal constant. Of course the temperature will come up, hopefully
not surpassing 42 °C. Low temperature = longer lifetime.
Your osc. Adev values are similar to mine, that should be ok (good).
I can confirm the experience by Warren. I use 490 s,0.68 damp factor and
a gain of -3.55 Hz/V actually resulting to

PPS ADEV
@ 1 tau 5.096E-11,
@ 100 tau 3.05E-11,
@ 500 tau 6.43E-12
@ 1000 tau 2.92E-12

Osc. ADEV
@ 1 tau 3.39E-09,
@ 100 tau 3.45E-11,
@ 500 tau 7.05E-12
@ 1000 tau 3.32E-12

read by Lady Heather, which does not mean that these values are exact!
This with the original OCXO, perhaps with an external oscillator one
could get better results, but I had no luck yet.

The PPS does very seldom exceed +- 5 ns, normally it does move just
around +- 2 to 3 ns. The DAC-Voltage changes are in the range of +- 3
steps of around 25µV (a step presesents close to 8 µV)

These are my observations, I hope it does help you.

regards,

Arnold


Am 19.08.2010 23:59, schrieb 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
> _______________________________________________