RE: [op25-dev] Control channel questions

Hi, Usually the uplink frequency is quite a bit away, and very often this is a fixed spacing. In Germany for example the uplink is, depending on the frequency band, 4.6, 5 or 10 MHz below the downlink. Ralph. From: op25-dev(a)yahoogroups.com [mailto:op25-dev@yahoogroups.com] Sent: Monday, May 8, 2017 5:44 AM To: op25-dev(a)yahoogroups.com Subject: [op25-dev] Control channel questions Hello, Let's say you're scanning the airwaves in the frequency range of a known P25 system and come across a spike in power at one particular band that never shuts off. * You should think that you've located a control channel, correct? * If so, is it safe to say that the upstream and downstream channels are side-by-side (one contiguous frequency band)? * What is the most accurate way of determining whether what you've discovered is a Phase I or Phase II system? * When someone keys up a radio, is the following sequence of events accurate?: 1. The radio sends a packet via the upstream control channel indicating that it wishes to speak. 2. The fixed site sends a packet via the downstream control channel indicating a frequency X on which it wants the speaker to transmit. 3. The fixed site sends a packet via the downstream control channel instructing all radios in the talk group to tune in to a frequency Y. 4. The speaker transmits on frequency X, and the fixed site acts as a repeater, re-broadcasting the audio to frequency Y. -- Alex