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<p><div class="WordSection1"><p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;">Hi,<o></o></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;"><o> </o></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;">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. <o></o></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;"><o> </o></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;">Ralph.<o></o></span></p><p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D;"><o> </o></span></p><div style="border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt;"><div><div style="border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0cm 0cm 0cm;"><p class="MsoNormal"><b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;">From:</span></b><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;"> op25-dev@yahoogroups.com [mailto:op25-dev@yahoogroups.com] <br><b>Sent:</b> Monday, May 8, 2017 5:44 AM<br><b>To:</b> op25-dev@yahoogroups.com<br><b>Subject:</b> [op25-dev] Control channel questions<o></o></span></p></div></div><p class="MsoNormal"><o> </o></p><p class="MsoNormal"> <o></o></p><div id="ygrp-mlmsg"><div id="ygrp-msg"><div id="ygrp-text"><p>Hello,<br><br>Let's say you're scanning the airwaves in the frequency range of a<br>known P25 system and come across a spike in power at one particular<br>band that never shuts off.<br><br>* You should think that you've located a control channel, correct?<br><br>* If so, is it safe to say that the upstream and downstream channels<br>are side-by-side (one contiguous frequency band)?<br><br>* What is the most accurate way of determining whether what you've<br>discovered is a Phase I or Phase II system?<br><br>* When someone keys up a radio, is the following sequence of events<br>accurate?:<br>1. The radio sends a packet via the upstream control channel<br>indicating that it wishes to speak.<br>2. The fixed site sends a packet via the downstream control channel<br>indicating a frequency X on which it wants the speaker to transmit.<br>3. The fixed site sends a packet via the downstream control channel<br>instructing all radios in the talk group to tune in to a frequency Y.<br>4. The speaker transmits on frequency X, and the fixed site acts as a<br>repeater, re-broadcasting the audio to frequency Y.<br><br>-- <br>Alex<o></o></p></div><div><p class="MsoNormal"><span style="color:white;"><o></o></span></p></div></div></div></div></div></p>
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