ARISS – Rx Only iGate

Last week,  I started experimenting w/ putting up a rig (and software) for servicing as “Receive Only iGate” for ARISS.  An RX only iGate will essentially operate in the mode of listening for APRS packets, and simply iGate them over to the APRS-IS server pool.  The RX only iGate does not do any level of TX of any capacity.  That is, when it iGates an APRS packet, you would not expect to see a RF TX to notify the world that it had iGated the packet.  The only trace you will find that it had igated was if you were to monitor the traffic in the APRS-IS servers (you could use my other app “APRS-IS client dashboard”) or via the aprs.fi or ariss.net websites.

With this project idea in mind, I had then purchased or downloaded the following materials:

• Raspberry Pi 2
• TNC-Pi (check out John Hansen W2FS site)
• YAESU FT-2900 (Low power Tx. Tx is not at all required in this example, except if you were to include a beacon)
• a cheesy on -roof-top JPole antenna – but, works great (soon to be migrated over to a dedicated Comet-GP9)
• cables, monitor, keyboard, etc to connect to RASPi and RASPi to radio
• XASTIR software
• SIMPLE-SAT (check out Tom Doyle’s W9KE site) — ISS satellite pass thru monitoring software (just to watch for testing purposes)

I had then tuned up my radio to 145.825Mhz, set up the XASTIR software, configured the TNC-Pi, and let it roll.

I then did a few tests and the below is the report of that project in its current state:

Ok…quick update folks.

The tests w/ ISS pass-thru last night went successfully.  I was able to igate 4 stations, received one ping back ACK from ARISS repeater RS0ISS.  The packets that were iGate happened *after* their packets got digi’d past thru the “RS0ISS” digipeater (this is the expected behavior).  So, the ISS Rx Only iGate is officially a “go”.  To summarize this portion of the project, the following is the spec notes:

1. RASPi 2 w/ TNC-Pi
   1. Running XASTIR in RF->Net mode (neither TX nor Digipeater features is active – not needed for Rx iGate operation)
   2. VIA path in XASTIR is set to WIDE2-2 (if I had a beacon, I would include “ARISS” in the 1^st VIA PATH).  But, in an Rx only iGate, the ARISS path is not needed
   3. iGate Server I’m connected to is “first.aprs.net” 14580 port. Creds are my call-sign and issued passcode
2. Radio details:
   1. The Radio is Yaesu FT-2900 running in Low Power (since Rx only) attached to RASPi and TNC-Pi
   2. Listening on 145.825Mhz
   3. Currently a cheesy JPole antenna.  Soon to be migrated over to a dedicated Comet GP-9

Next Steps:

1. Set up a beacon that is “Predictive Beacon”
2. I am writing a small C# app that
   1. It parses the TLE (Two Line Elements from http://celestrak.com/NORAD/elements/stations.txt) and extracts for “ISS (ZARYA)” data and applies the “pass-thru prediction algorithm”.  Following which, I would have the date/time/pass-thru-duration and/elevation angle datum
   2. The above pieces of data is used to then programmatically, issue TNC commands (check out Larry Kenney, WB9LOZ) to enable “UNPROTO CQ VIA ARISS” beacon.  Once every min and STOP once the APRS-IS server hears the entry. OR, stop soon after the pass-thru expires the time window.
   3. The above beacon also keeps in mind the elevation angle and can be configured to only activate if the angle is btwn a certain range.

Couple of screen shots

The following is a dump of the ARISS.NET traffic catalog   and the one latter is from APIRS.FI site

Thanks for following w/ me on this project, there’s more going on here in the next few weeks.  Please stay tuned and let me know your ideas, thoughts, etc.

73, N0AGI