[time-nuts] Some results of PRS10 and Trimble Resolution

SAIDJACK at aol.com SAIDJACK at aol.com
Wed Jun 28 16:47:46 EDT 2006

Hello Tom,

> Sounds good. Given that you still have many ns of
> jitter in  the 1PPS output you might want to consider
> dividing your OCXO down to  1PPS and using that for
> your master 1PPS user output; you can reduce  the
> output jitter 1000x that way. This is what HP did.

Yes, we do this, the 1PPS can be OCXO generated and adjusted to  +-10ms of 
UTC with 16.6ns resolution via the keypad (or RS-232). We could make  it 
adjustable to +-500ms with a small software change, but thought +-10ms range  is 
probably enough.
Does anyone here see a need to make the 1PPS output fully user adjustable  to 
+-500ms of UTC?
> The longer
> you average the less this is a problem; 10 or  30
> minutes makes it a non-issue. But with much
> shorter averaging  times you can see how it might
> cause trouble.

Our unit is completely configurable via the LCD and keypad, you can set any  
loop parameters such as loop time constant, Proportional gain, Integral gain,  
Tempco compensation, Oscillator drift/aging etc via keypad commands. Setting  
averaging times of 10, 30min, or even hours is easy. 
Thus the user can decide what is more important: frequency stability or  
phase accuracy to UTC, and adjust the loop parameters accordingly.
> The 8-bit 1 ns resolution part from Dallas/Maxim looked
> pretty  cheap to me. $5, I think.

But wouldn't a 1ns delay line also require a TIA with at least <1ns  
resolution to make full use of the delay line resolution?

> Note the 58503 and Z3801A receivers (now ten years
> old)  have 100 ps resolution. But I'm guessing your
> 3.33 ns detector is  cheaper than HP's!

Very true, ours is cheaper and simpler (more reliable?). We retail the unit  
at $750 new in small quantities, versus HP's units which sell used for 
sometimes  over $3K, see for example:
At the same time our OCXO and GPS receiver is much better than the one  used 
on the 58503A, so our ADEV and Phase noise is significantly lower (ADEV  is up 
to 8x better 100s to 1000s, phase noise is >10dB lower) than  the 58503B for 
Some other improvements are:
   * our power consumption is 4.5W at 12V, the 58503B is <35W  at 110V.
   * We have a 12 channel GPS, the 58503B is an 8 channel  GPS
   * Harmonic distortion for us is: <<45dBc, for  58503B its <25dBc
   * Spurs ("non harmonic distortion") for us:  <<100dBc, for the 58503B its 
But I don't want to brag :)

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