General Dynamics C4 Systems URC-200 (V2)
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3.0 PRINCIPLES OF OPERATION
3.1 Transceiver Functional Description
The URC-200 Transceiver operates in VHF and UHF frequency bands in either AM or FM modes.
Standard VHF band of frequencies in AM mode is 115 to 149.9950 MHz. In FM mode standard
VHF band of frequencies is 115 to 173.9950 MHz. Standard UHF band of frequencies in both AM
and FM modes is 225 to 399.9950 MHz. The URC-200 transmits and receives both plain text (PT)
and encrypted voice or data messages (Cipher Text - CT). See Table 6 for operational frequency
based dependencies.
There is also an optional software-enabled 400-420 MHz extended UHF FM-only mode, both PT
and CT. Finally, there is a hardware-based Low VHF 30-90 MHz option, FM-mode only, both PT
and CT.
Standard VHF/UHF band tuning increments are 5 kHz, 12.5 kHz, and 25 kHz. There is also a
software-enabled 8.33 kHz tuning increment option available for the standard VHF/UHF bands .
The 400-420 MHz option has tuning increments of 5 kHz, 12.5 kHz, and 25 kHz. The 30-90 MHz
option only has 12.5 kHz and 25 kHz tuning increments.
Where the 8.33 kHz tuning increment option is available and enabled, there are two receive channel
spacings (IF filter bandwidths) available in AM PT mode in the 117.975-136.975 MHz band (only):
8.33 kHz (narrowband) and 25 kHz (wideband). There are also two operating modes available
under the 8.33 option AM PT scenario: normal and “Aviation” mode. The former follows the
legacy URC-200 operation with the added capability of selectable channel spacing. The latter
makes the radio an 8.33/25 kHz channel spacing-only transceiver, and follows the ICAO Annex 10
Volume 5 standard for entering and displaying channels. The channel spacing is auto-selected
based on channel entered in Aviation mode and is not settable. The LCD display provides an
Aviation mode indicator and bandwidth indicators for this purpose.
Normal and Aviation mode are selectable by holding down specific keys during power-up, with
each mode applied “globally” to all channels, and maintained throughout power cycling, until de-
selected. They are also remotely selectable while the radio is turned ON.
The radio employs transmit pre-emphasis and receive de-emphasis in FM PT mode in the 132-
173.995 MHz and 400-420 MHz bands to improve overall signal-to-noise ratio, by correcting for
signal magnitude distortion across the frequency band.
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