8031 based repeater logic.


On power up, three pips are sent followed by the callsign and the letter "C" to indicate 77Hz CTCSS. If the repeater is running on battery power, the letter "B" is appended.


The repeater will then loop waiting for access attempts and give a periodic callsign every few minutes. You cannot access the repeater whilst it is sending the callsign, watch out for this if your receiver uses CTCSS.


If the squelch is open at the end of the callsign then the letter "J" is sent ("Jammed").


Accessing the repeater.


If a carrier appears with either a 1750Hz toneburst (BL only) or 77Hz CTCSS tone, the repeater will turn on the transmitter and relay the audio. If you use a 1750Hz toneburst, note that it is notched out by the repeater so you will have to wait for it to finish before speaking. Further tonebursts are not required until the repeater drops out. If you use 77Hz CTCSS, this must be left on all the time.


If the initial carrier is on for less than four seconds, the repeater will drop carrier at the end instead of latching on; otherwise it is successfully accessed and will continue to relay the audio until either the user drops carrier or they time out after four minutes.


When the user drops carrier, if they have been on for more than four seconds then  a PIP is sent after a half-second wait (courtesy delay) and the time-out timer is reset. If they have been on for less than four seconds, no pip is sent and the timer is not reset.


If the repeater is operating on batteries, the letter "B" is sent instead of the pip.


If sufficient "talk time" has accumulated, a callsign will be sent before the pip (this is to conform to the UK license guidelines). You may speak over the callsign, however the timer is not reset until the over pip is sent at the end.


If no-one uses the repeater, it will hang for 20 seconds then close down with a callsign. You may speak over the callsign and if you are using CTCSS you will immediately re-access the repeater at the end.


77Hz CTCSS tone is radiated by the repeater when it is in use. During the initial start of each over (the first four seconds) the CTCSS is switched by the incoming squelch. After that, it is forced on permanently until two seconds after the pip. This allows you to hear the pip and associated callsigns, but not relay blank carrier or the close-down callsign.


Timeout Operation.


If a carrier persists for more than four minutes ('BF) or nine minutes ('BL), the repeater will time out.


The onset of timeout is indicated by eight short pips over the user's audio followed by a callsign. If the input signal drops during this period then the repeater will finish the pips or callsign, then give the normal "over pip", The operation then continues as normal.


If, however, the input signal does not drop, then the relayed audio is cut off but the repeater's transmitter stays on. The repeater enters a non-re-accessible phase of 40 seconds during which time the callsign is sent every ten seconds followed by a pip and the received audio relayed (so you can hear who or what is jamming the repeater).


After 40 seconds, the repeater drops carrier and enters the second phase of the timeout. The callsign is sent every 20 seconds followed by two pips, again with the received audio relayed. This phase of the timeout is re-accessible as follows:-


a) if the user is not using CTCSS, then a stronger signal who IS using CTCSS can re-access the repeater.


b) A stronger signal with a 1750Hz toneburst can re-access the repeater.


If the input signal persists for a long time, the repeater will eventually close down and go back to the usual idle sequence, sending "J" at the end of the callsign.


Dave Hill June 2005.