MB7UBN - APRS Igate for Bolton and north Manchester
MB7UBN - APRS Igate for Bolton and north Manchester
Recently we set up an internet gateway or Igate for the worldwide amateur radio APRS (Automatic Position Reporting System) network to provide coverage for the Bolton and north Manchester area.
APRS is an international network of amateur radio stations providing real-time GPS based vehicle or event position reporting, weather reporting and simple message handling for educational, experimental or emergency use. APRS uses a common radio frequency of 144.800 MHz throughout Europe. An internet gateway provides a two-way port to the internet so that stations local to the gateway can be seen by others via the internet using APRS viewing programs such as Xastir or UI-View. The Bolton Igate MB7UBN is widely used by members of the local RAYNET amateur radio emergency communications group.
A selection of older "obsolete" equipment have been used to build the gateway and this web page has been written to encourage other radio amateurs to build similar APRS Igates.
The radio transceiver used is a FDK Multi-750XX. This is a 1980's vintage multimode 144 MHz transceiver that was unusable for normal use due to a faulty digital frequency readout. This has been set up on 144.800 MHz and provides about 16 Watts of RF power at the antenna, a Sharmans X-200 colinear omni-directional antenna. A Kantronics KAM Plus TNC unit sourced via eBay is used to interface the radio transceiver to the computer, a Panasonic CF-71 Toughbook PC (266 MHz Pentium 2 with 162 MB RAM) with Wi-fi access over our office network to a broadband internet connection. The computer originally used Xubuntu, a "lightweight" version of the Linux operating system suitable for older slower machines that can be downloaded for free here. The program used for the APRS internet gateway is Xastir. This program can also be downloaded for free from the Xubuntu software repositories.
To optimise the Igate program for use with a relatively slow PC the Xubuntu screensaver has been disabled, the Xastir map function has been disabled by deleting the Online directory from the /usr/share/xastir/maps directory and the internet server host chosen is ahubswe.net with port 14578 to restrict the internet feed to just the UK and Ireland. To provide an Internet to RF service to local stations a text file nws-stations.txt has been added to the hidden directory /home/----/.xastir/data. The text file lists the callsigns of local stations. This allows traffic received via the internet for those stations to be ported via the Igate to RF. When local mobile stations on the list go out of RF range of the Igate any position reports received from other Igates via the internet are ported to RF to give their remote location to other remaining local stations. Click here for a sample nws-stations.txt file.
After running continuously for 34 days the system load monitor revealed that the CPU load was 10 to 12%, 132 MB out of the 155 MB RAM available was used and 6 MB of swap file had been used.
In May 2007 the Igate computer was changed to a Panasonic Toughbook CF-25 Mk 3 using UI-View running on Windows 2000. This allowed the Igate to be set up as a full digipeater as well as an Igate. This was to provide an additional service to local Greater Manchester RAYNET members. The digipeater was set to repeat on RELAY, RAYNET, TRACE and WIDE so that packets from any APRS setup could be digipeated for emergency traffic even if it didn't meet the latest European APRS specification.
LATEST NEWS! 2 October 2007
From the 10 October 2007 MB7UBN will be operating just as a digipeater while changes are made to the broadband feed. Normal APRS coverage should not be affected as local stations digipeated via MB7UBN will reach the internet via three other APRS Igates in range of MB7UBN. These are MB7UZS Southport , MB7UCW Crewe and MB7USA Widnes . Contact Chris via info@
LATEST NEWS! 7 October 2007
Recently amateur radio equipment on board the International Space Station (ISS) has been set up to digipeat amateur radio APRS packets on 145.825 MHz. Bob Bruninga, WB4APR the inventor of the APRS system has made an appeal for radio amateurs worldwide to set up internet gateways on 145.825 MHz to forward the signals received from the ISS to the internet. You can't refuse an appeal from the guy who invented APRS so we have set up a ISS receive only internet gateway using the callsign G4HYG!
The old Toughbook laptop running Xastir on Xubuntu was put back in service using a KAM Plus TNC and an old and battered AOR AR-2002 scanning receiver. Initial trials proved that the system worked OK so a system to share the X-200 colinear antenna between two receivers was required. A modification was made to the FDK Multi-750XX transceiver used for MB7UBN to cut into the coax feed to the receiver front end after the transmit / receive antenna change over circuit. The receive RF feed was taken out of the transceiver to a custom built antenna distribution amplifier. The amplifier uses a BF981 low noise mosfet amplifier feeding a resistive splitter that provides two outputs for the FDK Multi-750XX transceiver and the AOR-2002 receiver. The receive performance on both equipments is now better than the original due to the low noise performance of the amplifier.
Does it work? Yes! On a recent ISS pass over Europe 68 packets were received by 6 Igates in Europe and sent to the ARISS
website that records ISS traffic. 40 packets were received by our Igate and sent to the internet. 19 of the 68 packets recorded on the ARISS website were from our Igate, G4HYG. The other 21 packets sent were duplicates of packets sent to the internet by the other stations acting as Igates at that time. The other Igate stations were ON7EQ in Belgium, EA4EKH-6 in Spain, G1LEV in southern England, PD0RKC in the Netherlands and OE3XUR in Austria.
The signals from the ISS varied in level during the pass due to changes in the distance between the satellite and the ground station, relative antenna polarisations and antenna shielding in certain directions on the ISS. Even with 6 Igate stations monitoring the pass I'm sure that some packets were missed. I can only repeat the appeal for more stations to act as Igates. Many of the amateur stations operating on APRS through the ISS are well out of range of the terrestial APRS network and broadband internet network so it's a way of helping others to join in.
The G4HYG ISS Igate will now run 24/7 with a short break while changes are made to the broadband connection.
LATEST NEWS! 27 October 2007
The broadband connection has been restored so both MB7UBN and G4HYG Igates are working again. The "short break" ran to 20 days! Many thanks to Ross, G6GVI who ran a receive only Igate for most of the time to to ensure that the RF transmissions from MB7UBN running as a digipeater always had a path to the internet.
Latest News 9 February 2008
We have added a 30m receiver to the Igate to pick up APRS packets on 10.1492 MHz. The receiver is an Icom IC-R71E HF communications receiver feeding into the HF port of the Kantronics KAM Plus TNC used for the VHF Igate. The antenna is a temporary one, just a 1/4 wavelength of wire running horizontally out of the window to the garden fence! Tests so far have been good considering the amount of electrical noise picked up by the poor antenna. The plan is to replace the temporary antenna with a 1/4 wave vertical ground mounted well away from sources of interference.
The callsign MB7UBN has been issued by Ofcom as a Notice of Variation for unattended 24 hour operation on the amateur radio callsign G4HYG held by Chris Moulding. Contact Chris via info@
Click here to see where Chris is using APRS on 144.800 or 145.825 MHz!
Click here to see where Chris is using HF APRS on 10.1492 MHz!
Click here to view recent APRS users of the MB7UBN Igate.
APRS is a trademark of Bob Bruninga, amateur radio callsign WB4APR. Click here to view Bob's website.