This discussion paper is designed to set out recommended procedures for licencing and configuring iGates for use on the APRS network in New Zealand. Such papers would be applied only as a gentlemen’s agreement. Adhering to them would be to the benefit of all amateur radio and APRS operators in the country.
APRS is an RF based tactical information system using AX.25 packet radio on 144.575.
APRS-IS is an internet network making APRS data available to web based browsers.
iGate is an RF to Internet or Internet to RF connection, usually (but not always) made up of a PC connected to the internet and a radio.
IS>RF – APRS data propagating from the internet to Radio Frequencies
RF>IS APRS data propagating from Radio Frequencies to the Internet
144.575 is the nationally recognised APRS frequency
Digipeater – A simplex store and forward AX.25 packet repeater. For the purpose of this document they receive and transmit on 144.575 unless otherwise stated.
Tracker – A unit comprising of a radio (on 144.575), a GPS, and some circuitry (also refered to as a tracker) connecting the 2 together. Such trackers beacon out position information from the mobile station, so other users can see where trackers are located on a map.
Licences. As per the amateur GuRL, all non attended transmitters with in the amateur spectrum require a licence. (eg Repeaters, Beacons and Links). iGates not located at an amateur radio operators address is considered a non attended station, and thus would require a licence to be applied for, granted and paid for.
Consultation has been had with APRS users around the counrty via the email ZLAPRS reflector, directly with APRS users via email, and by attending the Te Puke June meeting discussing issues with APRS users from Rotorua, Tauranga, Hamilton and Te Puke.
1) Receive Only. There is no issue with RF>IS traffic. As this is receive only (RF) this requires no licence. However it can create issues in the APRS network in the case of messages. Messages received by such receive only nodes will not be returned, as the APRS network sends replies via the same node, however will not be able to do so if such nodes can not transmit.
2) iGates that receive 144.575 data, but transmit messages only, overcome this problem. But as they are now fitted with an active transmitter they may require a licence.
3) iGates that receive and transmit all tactical information from ZL. This can create congestion as this information takes time to transmit and can make the APRS frequency congested with data, making it difficult for local traffic (mobile beacons etc) to find airtime to access the network. This is even more of an issue with hidden transmitters. Digipeaters are located on hilltops, and can hear more than what local stations can hear. Thus the mobile tracker may presume the air is clear when infact the digipeater is busy hearing iGate traffic. Packets will be lost. These iGates are known as ZL wide iGates.
4) iGates do the same as above but restrict the information they transmit by the way of a filter. Thus other than transmitting ZL wide traffic they may only transmit packets heard within a certain radius (say 200km). This limits the amount of traffic they will transmit. It should be noted that if an iGate hears packets on the air, it will not consider retransmitting them. This limits the amount of traffic such iGates will transmit to an acceptable level.
5) ZL wide iGates have their power set low enough so they are just heard by the nearest digipeater. This means that mobile trackers should overcome the igates signal into the digipeater to be heard. It does limit the useful transmitting range of the iGate station.
6) Another option suggested has been to use an alternate frequency to transmit IS>RF traffic ZL wide. This has been experimented with on 432.575 (70cm equiv of 144.575). A message only iGate is still required on 144.575 for full functionality, with the addition of being able to receive ZL wide traffic on an alternate frequency. This is useful for APRS users that have no internet connection at home, without degrading or congesting 144.575.
iGates 1-5 are on 144.575. igate 6 may be on any other frequency.
iGates at home. Most of the iGates in operation in New Zealand are currently located at a licenced amateur radio operators home address. They are assumed to be covered by the amateur GuRL. Thus there is no licence process to go through. It is however expected that iGate operators would look favourably to operating within NZART recommendations.
Interference. Stations (whether licenced or GuRL’d) causing interference may be open to an interference complaint lodged against that station.
iGates fitting option 2, 4 or 5 should be granted licence if one is requested, with the appropriate restrictions denoted on the licence.
iGates fitting option 3 should be declined, requesting that the applicant adjust their methods to fit option 2, 4 or 5.
iGates fitting option 6 should be granted, providing that the licence frequency chosen fits other band plan and interference mitigation criteria.
iGates not requiring a licence should still fit into option 1, 2, 4, 5 or 6 to be safe from interference complaints. iGate type 3 owners should be encouraged to migrate to an alternate option for the benefit of amateur radio and APRS.