The FireFox Desktop unit uses the same FireFox OEM board that is also sold separately. The desktop unit
includes a Swiss-made enclosure, a power supply, an LCD Display, a Keypad, and external connectors for all
the I/O connections available on the FireFox OEM board. The FireFox OEM board is typically installed into a
user enclosure, and statically set to a fixed frequency, or controlled via the built-in RS-232 serial port.
Back to Top
The FireFox synthesizer has five independent outputs to allow it to be used in almost any application that requires a highly stable and accurate analog sine-wave signal, or digital clock signal. It combines a function generator, signal generator, and GPS Disciplined frequency reference into one small unit. As a bonus, the unit also includes a generic, non-dedicated 2GHz mixer usable for building receivers, or up/down-converters.
The units' outputs are optimized for the following uses:
Yes, the FireFox keypad can be locked with jumper JP11.
Back to Top
You probably have turned off Fractional-N mode (see also "Resolution" FAQ under Performance section). With fractional-N mode disabled, the frequency granularity that can be generated is 1/65536 of the granularity when the fractional-N mode is enabled.
A warning message in the LCD display shows "FractOff" to indicate that the fractional-N mode is turned off.
When the fractional-N mode is turned off, the frequency will still be increased or decreased in 10µHz steps when pressing the UP/DOWN buttons, but the display will show the actual frequency that can be generated by the DDS (closest match to the desired frequency) once the button is released.
The advantage of turning off the fractional-N mode is that the system generates an exact mathematically deterministic
frequency without residual, fractional errors that are present in fractional-N mode.
Back to Top
The DDS system resolution below 2MHz output frequencies is about 1.7764µHz. The output frequency of the FireFox can be set by the user with 10µHz resolution. This step size when combined with the DDS internal resolution of 1.7764µHz creates an average residual output error of about +-0.8882µHz.
This error becomes more pronounced as the output frequency goes below 1Hz, with a worst-case performance when selecting an output frequency of 10µHz, which is actually generated as 10.6584µHz. The worst-case error at 10µHz output is thus a significant 6.58%.
With an output frequency of say 100Hz, the error due to the DDS resolution is about +-9x10-9, which is typically neglectable, but still above the FireFox OCXO accuracy when the system is locked to GPS.
An external CMOS, TTL, or PLD divider is recommended if extreme accuracy
for frequencies below 100Hz is required. This divider will allow the FireFox
system to run the DDS at a frequency of 100Hz or higher, preventing the
residual DDS error to become significant.
Back to Top
The front panel outputs have frequency range limits at which their outputs
are valid. The green LED's indicate when a particular output is valid and
usable. The CMOS and RF outputs are disabled outside of their operating
ranges. The LVDS outputs are active below their respective lower operating
limit (10MHz) in an under-scan mode. Operation of the LVDS outputs in under-scan
mode cannot be guaranteed, and the LVDS LED is thus turned off.
Back to Top
The FireFox unit is location sensitive due to the GPS receiver operating in location-hold mode. When factory new, the receiver averages ten thousand GPS readings to establish its permanent new location. This operation is done only once for every new location, or whenever the receiver has been turned-off long enough to discharge its internal backup batteries. It uses this location as a reference point for receiving the timing solution. Establishing a permanent position is called Auto-Survey mode, and operating with this location data is called position-hold mode.
For the FireFox unit to operate properly and within specification, the unit should be placed into Auto Survey mode any time its antenna is moved more than 30 feet (10m). This has to be done only once every time the receiver antenna is moved.
Placing the unit into Auto Survey mode also requires the antenna to have an unobstructed view of the sky for as long as it takes
to receive the ten thousand 3D readings that are required to establish the final position data. After the receiver has established
its permanent position, only one GPS satellite is required for synchronizing the internal OCXO, thus greatly relaxing the placement
requirements of the GPS antenna (please note that the receiver requires at least 4 satellites to be operational when the T-RAIM
timing mode is turned on).
Back to Top
The FireFox units have non-volatile memory that stores settings such as the frequency, amplitude, and menu options. This non-volatile memory does not require any battery backup. The unit will thus power-up with the last frequency and amplitude setting used prior to power-down.
Several important settings are stored in the GPS receiver and are backed
up by a rechargeable battery that has a life span of typically several days
when the unit is powered off. These settings are the position established
by the Auto-Survey function and used for position-hold mode, the time offset
from GMT, and the receiver operating-mode.
Back to Top
The FireFox units offer two output modes on the RF BNC connectors, relative and absolute output mode. The operating mode is selected in the "SETUP" menu. Relative mode allows controlling the output power from 0% to 100% of the units' capability, with the actual output power level varying with the frequency. This mode allows the user to harvest the maximum possible output power the unit can generate at any given frequency. Maximum power levels in relative mode typically range from +8dBm to +18dBm depending on the output frequency.
Absolute mode is used when highly accurate power levels are required. Absolute
mode sets the output power to factory-calibrated levels ranging from -40dBm
to +10dBm. The output power at the RF BNC connector is accurate to within
+-1dBm of the value displayed in the LCD over the units' frequency range
(+-0.15dbm typical accuracy).
Back to Top