FireFox Synthesizer User Manual
14
© 2006 Jackson-Labs
1.4.13.2 OCXO Timing Reference Output
The rear panel 10MHz time-base reference output is highly accurate, and disciplined by the GPS
receiver. This output is driven by a high-speed CMOS driver with 3.3Vpp output drive voltage. This
output may either drive a non-terminated 50 Ohm transmission line/cable, or it may drive an
end-terminated cable. The output voltage will be reduced by 50% if the BNC cable is end terminated
with a 50 Ohm resistor. See
Figure 1.2
for typical stability data for this 10MHz output signal.
The unit will require between 3 to 10 hours to stabilize fully when turned on from a cold-start. The
OCXO crystal may take up to one week to fully stabilize and to have periodic frequency shifts seize
to appear, especially if the unit has recently been moved, shipped, or has experienced significant
thermal changes.
The 30 minute Allan Deviation Estimate of this output is available in the FREQ EST display item
when entering the
STATUS->OCXO
menu item. This estimation is calculated by measuring the
internal OCXO generated 1PPS signal phase shift to the GPS generated 1PPS signal, and comparing
the momentary value to the value calculated 30 minutes previously. The deviation is then calculated,
and displayed in the LCD. Typical deviation numbers when the unit has been locked and operating
for several weeks are <+-5E-010 for the default OCXO option, and <+-5E-011 for the Double Oven
Ultra High Stability OCXO option.
1.4.14 Advanced GPS Setup
1.4.14.1 Factory Reset
Pressing the enter button in the
SETUP->GPS->FACTORY RESET
menu will initiate a GPS receiver
Factory Reset, and reset all of the stored settings of the FireFox Signal Generator. Please power cycle
the unit after initiating this command.
This command requires the user to re-initiate all of the settings such as Power Unit, GPS Time Offset,
Maximum Frequency and Maximum Power etc.
It is recommended that a Factory Reset is only initiated if the unit stops responding correctly to user
commands.
1.4.14.2 GPS TRAIM Filter
The GPS receiver can operate with an internal TRAIM (Time Receiver Autonomous Integrity
Monitoring) algorithm to ensure that data from bad Satellites will not corrupt the FireFox Signal
Generator Time Base accuracy. The receiver requires at least 4 Satellites to be received and to be in
good status when entering the
SETUP->GPS->GPS TRAIM FILTER
menu and selecting
GPS 1PPS
FILTER ON
. Any Satellite solutions with less than 4 Sats being received, or with any one Sat
exceeding 300ns deviation from the others will be considered stale by the GPS firmware when this
option is set to ON.
Jackson Labs recommends maintaining this setting in the OFF position when using the default
FireFox Signal Generator OCXO, and only setting this option to ON when using the
ultra-high-stability double-oven OCXO option with a GPS Antenna that has a clear view of the sky.
Summary of Contents for FireFox
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