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From: Art Sauer 
To: "'jimr@maia.usno.navy.mil'" 
Subject: Z12T Info
Date: Thu, 14 Feb 2002 09:33:32 -0800
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Status: RO


Dear Sir:
The Z12T will show as not locked because it does not have an internal
oscillator.  If the receiver is not using the external frequency, it will
not track any satellites.

Z12T Metronome Input Requirements


1) The 1PPS_IN signal should meet these guidelines:
 *Square-wave or pulse
 *5V-CMOS compatible levels (Vil = 1.5V; Vih = 3.3V)
 *minimum pulsewidth:  200 ns
 *1PPS definition:  Rising edge (default); Falling edge (selectable by
jumper setting on Metronome daughter board)

2) The 1PPS_OUT signal:
 *Compatible with 5V-CMOS levels and +15 dBm into 50 ohms
 *Pulsewidth:  1 - 2 ms, typical
 *1PPS definition:  Rising edge
 *Timing relationship, with 1PPS/PHOTO Time Correction = Y:
  1PPS_OUT is synchronized to the GPS Satellite Clock. 
  This is the standard GPS Navigation mode.
 *Timing relationship, with 1PPS/PHOTO Time Correction = N:
  1PPS_OUT mirrors the 1PPS_IN signal, plus propagation delays of internal
circuitry.


3)The Ref Frequency Input signal:
 *Frequency = 20.000 MHz
 *Waveform = Sinusoid, or 50% duty-cycle Square-wave
 *Input Power Range = +5 to +15 dBm

Additional Reading Material:
References for Z12T Metronome

Dach, R., T. Schildknecht, T. Springer, G. Dudle, and L. Prost, Recent
Results with Transatlantic GeTT Campaign", Proc. 31st  PTTI, Long Beach, CA,
1999.

Dudle, G., F. Overney, L. Prost, Th Schildknecht, T. Springer, P. Hetzel,
and E. Powers, "First Results on a Transatlantic Time and Frequency Transfer
by GPS Carrier Phase", Proc. 30th PTTI, Reston, VA, 1998.

Dudle, G., F. Overney, Th. Schildknecht, T. Springer, and L. Post,
"Transatlantic Time and Frequency Transfer by GPS Carrier Phase", Proc. 13th
EFTF 1999.

Overney, F., Th. Schildknecht, and G. Beutler, "GPS Time Transfer Using
Geodetic Receivers: Middle-Term Stability and Temperature Dependence of the
Signal Delays", Proc. 11th EFTF 1997.

Petit, Gerard, C. Thomas, Z Jiang, P. Uhrich, and F. Taris, "Use of GPS
Ashtech Z12T Receivers for Accurate Time and Frequency Comparisons, IEEE
Transactions on Ultrasonics, Ferroelectronics, and Frequency Control,
36:941-949, 1999.

Schildknecht, T, and T. Springer, "High Precision Time and Frequency
Transfer Using GPS Phase Measurements Using GPS Phase Measurements", Proc.
30th PTTI, Reston, VA, 1998.

Schildknecht, Th, and G. Dudle, "High Precision Using GPS Phase
Measurements", GPS World, 11:48-52, February 2000,
                                        Best Regards, Art
Art Sauer
Thales Navigation
email:  asauer@ThalesNavigation.com 
408-615-5218
800-229-2400, EXT 218