Sunday, April 05, 2015

Robust Packet Network

In my on going quest to equip my mobile with the best technological advantages available keeping me connected to the world through the use of the radio stack mounted in my mobile, I continue to move in that direction with the latest device added in the form of an SCS Tracker DSP/TNC.

In my blog post "Cross Country HF APRS" I described an HF APRS system that I implemented that gave me the capability to connect to the world wide APRS Network from anywhere my travels take me or under emergency situations.

Now having said that, I was aware that there is another HF APRS system available called "Robust Packet Radio" a much more robust form of HF APRS making it more likely for my packets to be delivered and heard by the various HF Gateways located world-wide on the 30 meter band.

Unlike "APRS Messenger" using PSK-63 that is configured through a software TNC, the RPR (Robust Packet Radio) system is only available through a hardware TNC built by SCS (Special Communications Systems) located in Germany, the developers of PACTOR used by Amateur and Marine radio operators for FSK transfer of digital information over the HF bands.

 Untill now APRS operations on HF has been done by ordinary HF-packets (FSK 300 baud), and with its small bandwidth, multipath propagation, phase shift, band noise and other disturbances such as fading and constant fluctuating conditions, transmitting digital signals via HF can be problematic at best.

Robust Packet has been designed to take advantage of the capabilities of digital signal processing (DSP) in order to obtain reliable communication over a less than perfect HF path. If you have only experienced traditional 300 baud FSK packet, RPR adds a whole new dimension to your experiences with packet. With the SCS tracker running conventional 300 baud FSK packet on one channel, and Robust Packet running on the adjacent channel, packet after packet was decoded while the conventional packet transmissions on the adjacent channel just flickered the DCD LED on the front of the tracker and were discarded due to errors present in the packet string.

The SCS Tracker RPR unit connected through the data port of a HF transceiver like my TS-480HX, is listening for packets being sent from other RPR stations. Once the SCS TNC has received and decoded this information, the tracker takes this information along with GPS data it is receiving from any external NMEA device like the Garmin Montana, and then sends this information as a APRS Datagram through the interface with the transceiver to HF Robust Packet Gateway stations listening on the network.

The SCS tracker also sends this APRS datagram back to the GPS receiver (Garmin Montana) that then decodes this information and places this information on the map visible on the screen in the form of a APRS symbol that describes the station with included callsign.
This system is also capable of bi-directional messaging when interfaced with a netbook running APRSIS32.

The 30 meter RRC (Really Rugged Coils) antenna mounted on the back deck of my Avalanche, is being used with my SCS Tracker DSP/TNC APRS Robust Packet station part of my radio stack.
The antenna has a dedicated 30 meter coil that I built expressly for the digital modes located on the high end of 30 meters.

The SCS Tracker and the Garmin Montana pared together are proving to be a great combination as utilized with my TS-480HX and its dedicated 30 meter RRC antenna.

 If you click on the photo for a closer look at the screen of the Montana, you can see the various RPR APRS stations that I am hearing across the US and further.
My RPR station VE6AB-9 is also being heard and gated through HF RPR Gates located across the world on the RPR 30 meter frequency of 10.147.30 MHz.
If you expand the map shown here you will see my mobile VE6AB-9 being heard and gated by W3LUZ-7 an HF Gateway located on the east coast of the US at a distance of 3088 kilometers from my mobile. Also listed there are a few of the other RPR stations that have heard my mobile directly and gated me.

NOTE... Since I wrote this post, I have since changed my SSID of "9" to "15" as there was confusion created using the same SSID with my Kenwood D710A on conventional packet, and also using the same SSID with my Kenwood TS-480HX on HF APRS.
The SSID "15" is used throughout the world signifying that the APRS station with this SSID is an HF APRS station.

I am extremely pleased with how my new HF APRS Robust Packet station is performing with my mobile being heard and gated from coast to coast across the US. I continue to run tests as I go down roads less travelled, and it is a pleasure to see the DCD LED on the front of my SCS Tracker light up upon hearing and successfully decoding packets being heard and then sent to the Garmin Montana and placed on the map keeping me connected with other RPR stations on the Robust Packet Network.
Note...all photos expand
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