from APRS-IS to RF,
• “Gate if source station heard via RF” - if enabled, the device will forward
packets from APRS-IS to RF even if source station was heard on RF. Should be
disabled,
• “RF heard buffer timeout [m]” - determines the time (in minutes) after which
stations heard from RF are removed from the “RF heard” buffer.
We need to store callsigns of stations heard from RF because:
1) If a station is heard from RF and “Gate if source station heard via RF” is disabled,
then non-message packets from such station will not be forwarded from APRS-IS to RF.
2) When a message packet sender is heard by our station from RF, then its message
shouldn't be forwarded from APRS-IS to RF (because we heard this station before from RF
so it is somewhere nearby and probably has already sent the same message packet
directly to RF).
• “Max. packets per 1 / 2 / 3 min” - maximum number of packets forwarded from
APRS-IS to RF in 1 / 2 / 3 min time periods. This option limits number of packets
forwarded from APRS-IS to RF to prevent channel abuse.
• “Filter setup” - this is a filter for non-message packets sent from APRS-IS to RF.
By default all packets are denied. Then filter entries are processed from first to
last field checking for allowed packet type and station. Possible entry types are:
• Not used – this field will be skipped,
• Allow all – all packets will be allowed from station defined in callsign/ssid
fields,
• Deny all – all packets will be denied from stations defined in callsign/ssid
fields,
• Beacons – beacon type packets starting with '!', '/', '=', '@' symbols from
stations defined In callsign/ssid fields,
• Destination – all packets with destination field defined in callsign/ssid
fields,
• Telemetry – all telemetry parameters message packets (PARM, UNIT, EQNS,
BITS) from station defined in callsign/ssid fields.
Please remember that packets processed through above filter must first be received
from APRS-IS server. Therefore you should also use “APRS-IS server filter settings” string
(in APRS-IS Tab, default “m/40” should be good for initial tests) to tell APRS-IS server
that you want to receive anything.
APRS-IS to RF forwarding is a complicated topic. All above settings were introduced to
allow balanced and limited forwarding because RF capacity is much narrower than
internet and shouldn't be overflowed with unnecessary traffic. Default setting of this Tab
will allow you to forward everything from RF to APRS-IS (not dangerous) and forward
messages from APRS-IS to local RF stations (shouldn't generate a lot of traffic). Other
packets will not be forwarded from APRS-IS to RF.
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