[time-nuts] 20Hz p-p / 24 hours with a Mini-T

Bruce Griffiths bruce.griffiths at xtra.co.nz
Fri Jan 9 01:51:28 EST 2009


Miguel Checa wrote:
> Hi group!
>
> I need some opinions, counsel, help, whatever you can send my way:
>
> I need to maintain the Mini-T within 20 Hz p-p in a 24 h period. I use 
> T=450 and all is well until the thing starts to lose satellites one by 
> one and goes into holdover and after a while, the VCO voltage jumps to 
> the start value and with it the frequency (up to -150Hz).
>
> The antenna is not in a good place and it can't be moved, but if I 
> restart the Mini-T, all satellites that were grayed out come alive and 
> strong. Any clues?
>
> Thanks,
>
> Miguel
> W4/LU9AXC
>
>
>   
Miguel

20Hz is a fairly wide tolerance that one could easily maintain with a
good OCXO with periodic manual frequency adjustments of perhaps once per
year.

If the Mini-T never sees a sufficient number of SVs uninterrupted for
somewhat longer than 450 sec then you need to reduce T to a value such
that sufficient SVs are seen for longer than T.

Do you have anyu idea of sky coverage and maximum observed SV track lenghts?

Bruce




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