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Posted by Greg Knox on December 24, 2000 at 10:57:16: In Reply to: Re: First flaw and 780 vs. 2067 posted by JD on December 24, 2000 at 02:30:48:
When trunking the '780 only needs to acquire the control channel once when it first starts up or when a trunking bank is first enabled. It probably takes 5 seconds or so to actually acquire the control channel. After that, the radio remembers where it is and immediately goes to it when needed. As for acquiring a particular ID: The IDs active on the system are all included in the control channel data. It takes about 23 milliseconds to transmit a single channel assignment over the control channel. The radio collects enough control channel data to include all talk groups that might possibly be active. On a 30 channel system that might be up to 29 conversations at once. That would require about 677 milliseconds, if that's all that got transmitted on the control channel, but there are some housekeeping functions also transmitted. Consequently, the radio actually collects data from the control channel for about 1 second. Decoding the data probably takes a few hundred microseconds or so. If the radio is in Scan mode it must now check the IDs in the scan list(s) against those it just found active on the control channel. That maybe takes a few microseconds, if that. If in Search mode it just uses the first ID it found active, assuming it's not waiting for a response from the last transmission. After it determines which ID it wants to work with it tunes the radio to the channel associated with the desired ID. The associated channel was included in the control channel data. It probably takes at most a few milliseconds for the synthesizer to settle and tune the radio to the desired frequency and open the squelch. |
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