Digipeating APRS packets via the ISS using a Kenwood TH-D72a HT Radio

 

I will go through the basic steps to manually enter in the information required on the Kenwood TH-72a ham radio.  Once you have done this, all you will need to know is when the ISS is passing over your location, and you can digipeat messages, emails, and your location, from virtually anywhere in the world.

The HT can deliver 5 watts, and along with a good antenna such as a portable Elk or Arrow brand antenna work great throughout most of the pass, but also if the ISS is directly above you, I have been succesful to digipeat even with only a telescopic antenna on top of my radio.

 

Setting up the radio for APRS via the ISS

There are a few settings you need to change in the radio, in order to properly digipeat via the ISS.  If you have already used the radio for local APRS, some of these settings you may have already completed, but others may need to be modified slightly for ISS digipeating.  Turn the radio on....

 

- Set your callsign

This callsign will be part of the APRS packet, the SSID number after the callsign is not required, but it can assist others to know if you are transmitting on an HT, mobile, home, etc.  SSID 7 = walkie talkies, HT's or other human portable.

1. Press Menu 3 0 0
2. You should read Basic Set > My Callsign with blinking cursor on the callsign
3. Press Left and Right on navigation pad to move cursor
4. Turn the Tuning control encoder knob on top and scroll letters
5. Use the A/B button to clear/backspace
6. Add a - and a Number for your SSID (ie: KC9BUD-7)
7. Press the Right navigation pad to move the cursor to the right when you are done
8. Press Menu to exit

 

 

- Set Station Icon not sure if this is needed

This is an icon that will appear when others receive your packet, also this is the icon shown when you view your location on http://aprs.fi/.

1. Press Menu 3 C 0
2. You should read Icon > <icon names>
3. Turn the Tuning control encoder knob on top to scroll icons
4. Press Menu twice to exit

 

- Setting Beacon Information

Because we will digipeat through the ISS, we will not be auto beaconing our location, to minimize traffic.  We will only send manual messages, so we will turn beaconing off.

1. Press Menu 3 D 0
2. You should read TX Beacon > Methos
   
3. Turn the Tuning control encoder knob on top to turn beacon to Manual
4. Press Right on navigation pad for OK
5. Press Menu to exit

 

 

 

- Setting a Position Comment

Although we will not auto beacon our location, it is a good idea to make sure that this is not set to EMERGENCY, in the event later you do have a need to beacon your location.

1. Press Menu 3 8 0
2. You should read Comment > Position Comment
3. Turn the Tuning control encoder knob on top to scroll through available messages
4. Press Right on navigation pad to select
5. Press Menu to exit
6. *Note do not use EMERGENCY! during normal operation

 

- Setting APRS Path

In local terrestrial APR we typically will use a path of WIDE2-1, but for the ISS, we need a custom path set to RS0ISS, although using ARISS as the path has also worked for me in the past, it is not recommended.  - RS zero ISS

1. Press Menu 3 H 0  you will need to use the scroll knob on top and the navigation pad to enter the letter "H", ie: press menu, "3", then scroll to "H" then press Right on navigation pad.
2. You should read Packet Path > Type
3. Turn the Tuning control encoder knob on top to scroll through available options
4. Select Others for your path
5. Press the asterisk key * so it appears before Others, to signify that this is what we will use as the path
6. Press Right on navigation pad to select
7. Press Down on navigation pad to select PATH
8. Press Right on navigation pad to edit the path
9. Press Left and Right on navigation pad to move cursor
10. Turn the Tuning control encoder knob on top and scroll letters
11. Use the A/B button to clear/backspace
12. Using this method, enter in RS0ISS, note this is a number Zero 0, and not letter O
13. Press the Right navigation pad to move the cursor to the right when you are done
14. Press Menu to exit

 

- Setting the TNC Baud rate

Standard APRS uses 1200bps as the baud rate, the Kenwood also allows 9600bps, so we need to ensure this is set properly to 1200 bps.

1. Press Menu 3 1 0 
   
2. You should read Int. TNC > Data Band
   
3. Turn the Tuning control encoder knob on top to scroll through available options
4. Select A-Band as we will use VFO A when we transmit later
5. Press Right on navigation pad to select
6. Press Down on navigation pad to select Data Speed (which is the baud rate)
7. Press Right and turn the control knob to select 1200 bps
8. Press the Right navigation pad to move the cursor to the right when you are done
9. Press Menu to exit

 

Tuning the VFO to the proper frequency and turning on the TNC

Now that all of the basic APRS settings are set correctly in the radio, we will set the radio to a single VFO and tune into the ISS APRS frequency 145.825 MHz.

 

- Set the radio to single VFO mode

The Kenwood has the ability to use dual VFOs, for simplicity, we will set it to a single VFO, A

1. Press DUAL This will toggle between dual and single VFO mode, you want to select when only a single frequency is shown on the screen
2. Press A/B to select which VFO, in our case we will select "A", which will show the Frequency on the first line, date and time, on the second line

 

- Set VFO A to VHF and select the proper frequency

Each VFO has the ability to be set to VHF or UHF, we will use VHF

1. Press the functon key  F  then A/B key.  This will toggle the VFO between VHF and UHF
2. Use the Tuning knob encoder to scroll to the proper frequency of 145.825 MHz.  You can also press ENT and then the frequency on the keypad.

 

- Set transmit power to high

The Kenwood TH-D72 has 3 power outputs available, we will set to "H" or High

1. Press the function key  F  then Menu key.  This will toggle between the 3 power outputs, keep selecting these 2 key button presses until you read "H" on your screen.

 

- Turn on the TNC

The Kenwood TH-D72 has a built in TNC, it can also be used in 2 different modes, we will select APRS

1. Press the function key  TNC .  You should see a message "Opening TNC", keep pressing until you see APRS12 on top of your screen.  You will also see a 'D" after the frequency, indicating this VFO will be used for data.

 

Sending an APRS message via the ISS

Now the radio is all set, once you know the ISS is passing over your location, we will input a message and transmit the APRS packet.  Follow the pass with your directional antenna using various tracing software available.  You should be able to hear the APRS traffic, as the ISS is passing overhead.

1. Press the  MSG key twice  You should see MSG Input
2. Press Left and Right on navigation pad to move cursor
3. Turn the Tuning control encoder knob on top and scroll letters
4. Use the A/B button to clear/backspace
5. Use Dual/0 and then Right for a space
6. To: should be CQ
7. The message > can be anything you want to digipeat across ie: 73 de Algis KC9BUD EN52 Oakwood Hills, IL
8. 73, de <name> <callsign> <grid location> <city & state> 
9. To find your grid location, view the Confirmation/Troubleshooting section below
10. Once  you are done with your message, press the Right navigation pad twice, it will then put your message in the que, and begin to transmit up to 5 times as long as the squelch is closed, and not receiving.

 

Tracking the ISS

...to do

 

Confirming/Troubleshooting

...to do

 

Other fun things to do

...to do

 

 

 

 

 

References:

http://www.aprs.org/aprs11/SSIDs.txt

http://www.algissalys.com/amateur-radio/aprs-over-satellites