Raytheon SNV-12, Инструкция по установке и эксплуатации

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SNV-12 Operations Manual
5-2
In order for a new site to be voted, one SVM must detect a (selectable) better noise level or
SNR than the presently voted site, and maintain this difference for a selected voting transition
time.
Factory defaults for these settings are 1 dB noise level/SNR difference and a 250 msec voting
transition time. This means that if site A is presently voted, site B must maintain a 1 dB noise
or SNR advantage over site A for at least 250 msec. in order to be voted in place of site A.
Other “voting criteria” may be selected to fine-tune system performance.
Since the majority of voting systems use FM receivers, the factory default voting method is FM
Mode. This voting mode is also recommended whenever low to mid-range tones (below 2.2
kHz) are introduced into the audio spectrum for signaling purposes.
To set the SNV-12 to vote based on SNR (AM/HF mode), a dipswitch must be set on each
SVM. Note: All SVMs in a chassis must be set for the same mode; there cannot be a mixture of
FM and AM/HF settings on the modules.
5.6 Voting Transition Criteria
The SNV-12 will react and vote immediately when signals appear on a previously inactive
system (when the voter changes from all sites squelched to one or more sites unsquelched).
An adjustable delay timer sets when a voting transition can occur within a system that is
currently active (one site already voted). The voting delay settings are from 50 msec to 5
seconds. The purpose of longer delays is to restrict the number of voting transitions that occur
when signal conditions vary rapidly. This voting delay time is set by CPM module switch
SW4, a 16-position rotary switch.
In order to be voted over the presently voted site, a new site must also maintain a noise or SNR
advantage over the presently voted site for the selected transition time. This signal quality level
is adjustable, and set by CPM dipswitches SW2-1, 2, 3. See Section 3 for more information on
the noise and SNR differences, and on voting delay settings.
5.7 Audio Delay
The Site Voter Modules can provide a variable amount of delay to each RX audio path to
compensate for differences in the link delay between the satellite receiver sites and the voter or
to compensate for delays elsewhere in the system. This delay is set on
each Site Voter Module
by switch SW1, a 16-position rotary switch. The delay range is 0 to 450 msec in 30 msec steps.
Similarly, the CIM module can add delay to the console transmit audio. This ensures that all
audio and PTT signals are set and stable before transmit audio is sent through the voter and the
rest of the communications system. The same range of audio delay settings is available.
See Figure 5-1 for a pictorial view of the delay options; descriptions of each follow.