FireFox Synthesizer User Manual
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© 2006 Jackson-Labs
3.5.2 How does the FireFox handle GPS hold-over mode?
Other commercially available reference-timing receivers boast of their long hold-over circuitry
performance when not being able to receive any satellites. The FireFox synthesizer uses a slightly
different approach.
Instead of hoping for the best and designing circuitry for hold-over mode when the receiver cannot
receive GPS satellites due to jamming or due to the low sensitivity of competitive receivers, the
FireFox uses an optimized design and the best receiver available on the market to avoid any GPS
receiver drop-outs in the first place. Once the receiver has established its position and is in
position-hold mode, only one satellite needs to be seen by the receiver for the FireFox synthesizer to
work properly. The sensitivity and jamming immunity of the FireFox GPS receiver is absolutely
exceptional. Thus long hold-over periods will likely never occur even if the antenna is just placed in
a window sill.
3.5.3 Can the internal GPS receiver be connected to a PC?
The FireFox internal microprocessor controls and configures the GPS receiver with default settings
during power-on. A menu option allows access to the GPS serial signals via an RS-232 connector on
the back panel to override these default settings. This connector may be used to optionally control the
GPS receiver setup via Motorola’s WinOncore12 PC software.
All features of the internal Motorola M12+ receiver can be checked and controlled via a simple
null-modem serial cable. Antenna cable offset, satellite mask angles, timing information, satellite
health information as well as GPS vs. UTC time-base settings are some of the parameters that may be
controlled and checked via the PC software, overriding the FireFox default settings.
3.5.4 I can connect to the GPS receiver from my PC, but cannot
change any settings?
The FireFox GPS receiver is controlled by its internal microprocessor by default. You can monitor all
GPS parameters via WinOncore12 but you cannot change its settings in the default mode. To change
the receiver settings, go to “MENU/SETTINGS/COMMUNICATION/GPS CONTROL” and change
the item to “REMOTE”. You must stay in this menu item for as long as you want to change the
receiver settings via WinOncore12. Exiting this menu item will return the receiver to “LOCAL”
control, and you will again only be able to monitor the receiver parameters without being able to
change them.
3.5.5 What is the GPS Auto-Survey Mode?
The FireFox system uses a specialized GPS timing receiver. Instead of calculating the geographic
position, this receiver uses a fixed geographic position setting to achieve a very high timing accuracy.
When the present position is unknown (such as when the receiver was moved) the satellite receiver
will measure and average ten thousand position measurements to achieve a position average with
very high accuracy. This measurement mode is called Auto Survey Mode. The satellite receiver locks
into its final position-hold mode within 2.5-5 hours, after which it will receive the position-corrected
timing information from the GPS receivers. The Auto Survey mode settings are saved in NV
Summary of Contents for FireFox
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