MIL-PRF-49185B(CR)
3.5.3.6 Distortion (PCM). The radio set shall be arranged as in 3.5.3.5 with the receiver
coupled to the transmitter through sufficient attenuation so that the RF input at the receiver input
terminals (including duplexer) is -54 dBm. A sinusoidal signal at any frequency within the range
of 250 Hz to 240 kHz shall be applied at the video input terminals of the transmitter at a level of
2 V peak-to-peak. The transmitter shall be adjusted for rated deviation and the receiver output
shall be 3/4 plus or minus 1/4 V peak-to-peak at the unregenerated video output terminals.
Under these conditions the total harmonic distortion measured at the unregenerated video output
terminals shall not exceed a level 26 dB below the fundamental.
3.5.3.7 Pulse regeneration (PCM). The receiver output circuits shall generate new pulses
whose amplitude, timing and pulse shape are derived from the 6 channel or 12 channel signals
briefly described in Table IV.
TABLE IV. Pulse regeneration.
PCM characteristics
Number of channels
6
12
Signal Bit rate
(Full-baud, unipolar binary)
(Full-baud, unipolar binary)
288
576
Pulse width at half amplitude
3.472
1.736
3.5.3.7.1 Regenerated PCM. The regeneration shall eliminate all noise peaks less than
40% of the pulse amplitude for the range of unregenerated video output levels corresponding to
input deviations of +145 kHz peak minimum to ± 230 kHz peak maximum. The regenerated
signal amplitude shall be -0.1 V ± 0.1 V for the "1" condition and -2.0 V ± 0.20 V for the "0"
condition, delivered into a load of 91 ohms ± 5%, with no reversal of phase from the transmitter
input or unregenerated video output. Pulse width shall be full interval with 10% to 90% rise time
10 ns minimum, 50 ns maximum. The 50% point shall be 0 ns minimum, 80 ns maximum after
the 50% point of the rising edge of the timing signal specified in 3.4.3.7.2.
3.5.3.7.2 Timing signal. Timing signals shall be extracted from the incoming pulse train
and shall accompany the regenerated PCM to the next unit. The timing signal amplitude shall be
2V ± 0.2 V DC isolated, delivered into a load of 91 ohms ± 5%. Pulse width at the 50%
amplitude point shall be 80 ns minimum, 150 ns maximum. Rise time of the leading edge from
the 10% point to the 90% point shall be 20 ns minimum, 50 ns maximum. Pulse rate shall be
576 kHz for both the 6 channel and 12 channel signals.
3.5.3.7.3 Squelch and alarm. The squelch shall disable the regenerated PCM signal when
the signal-to-noise ratio at the unregenerated video output is less than 7 dB ± 2 dB when
measured as in 3.4.3.5, with a reference deviation of ± 180 kHz peak. The audible and visible
alarm shall operate in conjunction with the squelch to indicate locally, failure of the received
signal from the remote station. A reversing switch shall be provided on the front panel such that
regardless of the level of signal input to the receiver, the audible alarm can be disabled. The
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