N1SU APRS Digipeater & TX IGate

N1SU APRS Digipeater & TX IGate

Configuration and setup overview by Jason Buchanan

Seattle APRS frequencies

440.800 UHF - 9600 baud
144.390 VHF - 1200 baud

If you have a radio capable of UHF 9600 baud for APRS (Kenwood TH-D7A, TH-D72A, TH-D74A, TM-D700, TM-D710, TM-D710GA... others?) put it to good use! UHF APRS is alive and well in Seattle.

March 6, 2020

Replaced Raspberry Pi 3B+ board. Back to normal.

RCA: micro-USB connector had no strain relief and damaged the connector on the board. Need to get a proper case at Vetco.

March 2, 2020

Raspberry Pi failed - APRS nodes down

TNC-Pi on I2C would TX but RX was not working. TNC-Pi9K6 worked normally.

Rebooted Raspberry Pi while troubleshooting and was able to SSH after rebooting, but the Pi itself became a brick on the third reboot.

SD memory card gets very warm when inserted to the Pi, or to a laptop.

Raspberry Pi is completely unresponsive with only power and HDMI connected (no memory card inserted). Tried a known-good power supply and have the same results.

January 2020

Updated TNC-Pi and TNC-Pi9K6 parameters as shown below:

1200 9600
# 1200 ./pitnc_getparams 1 16 pitnc_getparams Version TNC Software Version 1 01 TXDelay - Zero means use ADC 30 02 Persistance 63 03 Slottime (in 10 mS) 20 04 TXTail 0 05 Full Duplex - Not used 0 06 Our Channel (Hex) 00 07 I2C Address (0 = async) Hex 10 ADC Value 33 # 9600 ./pitnc_getparams 0 0 pitnc_getparams Version Using Serial port /dev/ttyAMA0 TNC Software Version 8 01 TXDelay - Zero means use ADC 30 02 Persistance 63 03 Slottime (in 10 mS) 10 04 TXTail 0 05 Full Duplex - Not used 255 06 Our Channel (Hex) ff 07 I2C Address (0 = async) Hex ff 08 Mode Speed 9600 09 RX Level (Config) 0 10 TX Level 200 11 RX Level (Actual) 132 13 Centre Freq 2550

Notable values:

1200 - TXDelay 30 - (300ms) robust; below 30 reduces overall success
1200 - Persistence 63 - was 15; occasionally would not TX (bug?)
1200 - TXTail - not sure this needs to be anything but 0

1200 - TXDelay 30 - (300ms) robust; below 30 reduces overall success
9600 - Persistence 63 - was 15; occasionally would not TX (bug?)
9600 - TX Level 200 based on recommendations by other Yaesu FT-7800R users
9600 - TXTail - not sure this needs to be anything but 0

Persistence calculated as 256 / #slots - 1 or 256 / 4 = 64 then subtract 1 = 63

November 2019

Updated the crossband aprx.conf configuration file for reference.

October 2019

UHF APRS 440.800 9600 baud activity continues to grow. N1SU-4 statistics and N1SU-4 users show nearly as many APRS packets on UHF as VHF despite far fewer UHF APRS stations.

Click N1SU-4 then Coverage to see statistics and activity for 440.800. Also, note that UCAPK (66 miles away) and N7ER-10 (33 miles away) are outside of the shaded plot but are reliable paths. W7NWP-4 and N7RIG-5 are within the shaded plot and further enhance the meshed network.

You're really missing out if not using UHF 9600 baud for APRS - congestion is much lower due to the much shorter TX time at 9600 baud.

August 2019

APRS UHF VHF crossband digipeater configuration is in use. A single instance of aprx is used to provide digipeater coverage from UHF to VHF, and vice versa, including full APRS-IS internet gateway service.

The crossband aprx.conf configuration file (updated November 2019) is availble for online reference. This configuration includes weather and radiation monitoring via geiger counter sent to UHF and VHF every 30 minutes - this configuration provides interesting data to view propagation changes. The weather data is never sent via APRS-IS and this is intentional, as it intended to be received by UHF and VHF gateways.

The basics

Purpose: to provide Global APRS Messaging service in the Seattle area, supporting 2-way APRS messaging on VHF and UHF APRS radios.

N1SU-2 (VHF, 144.390) and N1SU-4 (UHF, 440.800) provide full duplex APRS digipeater and internet gateway services, allowing you to send messages and receive replies using only your radio, no internet or cellular service required.

N1SU APRS Network Configuration
N1SU-2N1SU-4N1SU-13RX/TX gatewayAPRS uplinkWeather stationRadiation monitor
Geiger counter
1200 baud
Kenwood TM-281A
Ham Made cable
9600 baud
Yaesu FT-7800R
6-pin DIN
aprx 2.9.0
weewx 3.9.2
9600 baud TX 440.800
aprx 2.9.0 aprsc 2.1.4 Davis Weather Monitor II
weewx and wmII.py
Aware Electronics
model RM-80
Raspberry Shake
model RS1D

Everything shown above runs on a single Raspberry Pi.

The TNC-Pi and TNC-Pi9K6 are stacked on a single Raspberry Pi 3 Model B+
aprx 2.9.0 is used for digipeater and APRS-IS internet gateway
weewx and wmII.py are used to read the Davis Weather Monitor II
Aware Electronics model RM-80 is used for gathering radiation rate as microRoentgen per hour, mR/hr - also at http://digistar.com/seattle/

N1SU-13 changes symbol to match APRS spec 1.2 for reporting the level of Nuclear Radiation levels, using type X. Quoted from the spec:

RADIATION LEVEL: The field Xxxx has been proposed for reporting the level of Nuclear Radiation levels if available. The X is the type indicator. We chose "X" for radiation. The xxx are like the resistor code. First, two digits of precision and the last digit is the order of magnitude in NANOSEVERTS/Hr. So 123 is 12 * 10^3 nanosieverts/hr or 12 microsieverts/hr. Or 456 is 45 * 10^6 nanosieverts/hr or 45 millisieverts/hr. One bananna generates about .1 uSieverts/hr, a Brazil nut .4 uS/hr. If the radiation is at background levels the /_ weather symbol may be used, when elevated readings occur, the R_ weather symbol with "R" overlay will indicate a Radiation Sensor weather station. When a hazard threshold has been reached, the symbol can change to a RH symbol (Hazard with R overlay).

Getting started with Aprx

I put together a page about the aprx.conf and general aprx configuration. Hopefully it will provide some help to those getting started with aprx.


Be sure to check out the NWAPRS Northwest Automatic Packet Reporting System - NWAPRS serves: Alberta, British Columbia, Northwest Territories, Washington, Oregon, Idaho, and Montana

I created a mailing list for APRS UHF discussion, to possibly coordinate a nationwide UHF frequency for APRS, and general APRS digipeater and internet gateway topics.

Enter your email address in the box below to join the group.

Google Groups Subscribe to aprs-uhf
Browse Archives at groups.google.com

N1SU-3 was QRT 8-Jul-19 and became N1SU-2 (2 meters).

N1SU-4 (440MHz 9600 BAUD UHF APRS) was QRV 8-Jul-19.

N1SU APRS Digipeater & TX IGate overview - Updated: 27-Mar-22
(C) 2022 jsb@digistar.com

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