Viscous APRS Digipeater

Viscous APRS Digipeater is a modification of APRS Digipeater, which puts all packets heard from radio channel into a short term probation delay hold (4-8 seconds,) and checks to see, how many copies of that same packet (per APRS packet duplicate detection algorithm) will be heard during that interval.

If a packet is heard only once, it will then be processed like normal digipeater request. If a packet is heard more than once, it is silently forgotten.

At present (October 2009) only one software is able to do this: Aprx

With fresh Aprx v2, the necessary configuration is like follows:

 mycall  OH2MQK-1
 <interface>
    serial-device /dev/ttyS0 19200 8n1 KISS
    callsign  $mycall
    tx-ok     true
 </interface>
 <digipeater>
    transmit $mycall
    <source>
        source         $mycall
        relay-type     digipeat
        viscous-delay  5
    </source>
 </digipeater>

Graphs below show effect of enabling the viscous-delay 5 on digipeater configuration.

• Top graph is number of packets heard from radio.
• Mid graph is packets rejected by APRS Rx-iGate function (and unrelated to this topic)
• Bottom graph shows counts of packets transmitted by the digipeater subsystem.
  • Most notable is that this added viscosity to digipeater does reduce transmissions by 80 to 95 percent.