TIMTER™ Multi-mode Digital Telemetry Transmitter
14
Quasonix, Inc.
•
83421-9224 Micro-D 9 to RJ-45 (T568A standard), 1.2m
•
83421-9225 Micro-D 9 to RJ-45 (T568A standard), 10.0m
•
83421-9226 Micro-D 9 to RJ-45 (T568A standard), 3.0m
1.3.22 Analog Frequency Modulation
– FM
This option allows the TIMTER™ to function as an analog FM transmitter. In this mode, the analog input voltage is
converted to frequency offset, relative to the carrier, based on a settable deviation scale factor. No filtering or other
signal processing is performed, and commands and functions related to digital clock/data do not affect the
modulated output. This mode of operation is designed for use with a true analog signal, such as NTSC video. By
default, the analog FM input is AC coupled, with a low frequency cutoff of less than 15 Hz. Contact Quasonix if you
need a DC coupled analog input.
FM mode is not optimal for sending digital data; refer to the AI option in section 1.3.11 for that configuration.
However, if your TIMTER™ has only the FM option, and not the AI option, you can still use it to transmit digital
data, but you will not have the greatest benefit of the AI option: the internal bit sync is not available to set the
internal premod filter and deviation automatically. When using the FM mode to send digital data, the premod
filtering must be performed externally, and the deviation is set using the AFMS command (refer to section 1.3.22.1).
1.3.22.1 Using True Analog FM
Analog FM provides the capability of frequency modulating the RF carrier based on an analog input signal voltage,
making the Quasonix digital transmitter behave virtually identically to an analog PCM/FM transmitter (but with
improved phase noise, more precise deviation control, etc.). Analog FM requires the –FM option. The two
commands for controlling analog FM are MO and AFMS. MO 12 enables the analog FM input, and AFMS sets the
sets the deviation in MHz per Volt. (Refer to the Command Set section 4.2.1, for specific information about each
command.)
In order to use TRUE analog FM:
•
The –FM option must be in the part number
•
Mode must be set to MO 12
•
Use AFMS xx command to set the deviation sensitivity to xx MHz / volt; for example AFMS 1.0
Refer also to the Auxiliary Input option, section 1.3.11.
1.3.23 Frequency Offset
– FO
This option is used to set frequencies that are NOT aligned to the synthesizer step size for their units, typically 500
kHz, and it enables the FO user command. If the FO option is present, the resolution is 1 Hz (0.000001 MHz).
1.3.24 GPS Notch Option
– GN
Use this option to specify GPS notch filters to meet -147 dBm/Hz at L1 and L2 (hardware note). Available for S
band only. Consult Quasonix for pricing and availability.
1.3.25 High Bit Rate Option
– HR
The standard TIMTER supports bit rates from 0.1 to 28 Mbps in SOQPSK-TG and ARTM CPM modes, 0.05 to 14
Mbps in PCM/FM (Tier 0) mode and in all legacy modes. The HR option increases the bit rate to a maximum of 46
Mbps (23 Mbps for PCM/FM). Refer to the CF option for information about the Clock Free option.
Refer to Table 12 for bit rate comparisons by mode.
