GRBAlpha - How to use digipeater or DNxD - 09. About terminal software

Now you may catch and decode the signal from GRBAlpha. If you cannot, please check your connection, levels, etc., that I have already mentioned. After you succeed to decode, your next step is transmitting your message.

Because Direwolf or Soundmodem themselves do not have the function to send messages, you have to prepare a terminal software for transmitting.  UISS, Tunaterm, Teraterm or other terminal softwares, that have the function to connect to Direwolf or Soundmodem through No.8000, 8001 port, are enough for this purpose. I also built a simple JAVA applicaiton that has the function only to send messages. You can get this from here. This file includes a manual. Please check it before you use it. This application needs "Open-jdk8" or "Open-jdk11", so you have to install one of them in your PC.

GRBAlpha - How to use digipeater or DNxD - 08. Settings of Direwolf

"Direwolf" works on Linux or Windows. You can get information from here: https://github.com/wb2osz/direwolf
You can download windows version from here: https://github.com/wb2osz/direwolf/releases
In case of Ubuntu, you can install it from "Ubuntu Software".
Direwolf is designed especially for APRS, but we can use it as a software TNC.

The settings of Direwolf are very simple. You only modify "direwolf.conf" file.

First, I explain in case of Linux.

After you install "Direwolf", you may have a file named as "direwolf.conf" at your home directory of your Linux PC.
If you cannnot find it, you can download an original file from here.
After you download the "direwolf.conf" file, save it in your home directory. Then open it with a text-editor.

To use 9600bps, you must find:
MODEM 1200
#MODEM 9600
The "#" means comment-out. The above setting means you use 1200bps and disable 9600bps.
If you want to use 9600bps for GRBAlpha, change them to:
#MODEM 1200
MODEM 9600

To enable to use your PTT, you have to modify:
PTT /dev/ttyUSB0 RTS
so as to suit your equipment settings.
For example, change "ttyUSB0" to "ttyUSB1", or "RTS" to "RTS -DTR", etc.
Before you use PTT setting above, you should set the permission for normal user on /dev/ttyUSB0. You must run a command in the terminal window like as:
sudo chmod o+wr /dev/ttyUSB0

Next, I explain in case of Windows.

After you install "Direwolf", you will find "direwolf.conf" file in your folder you installed "Direwolf". Then open it with notepad or other text-editor.

To use 9600bps, the setting is the same as Linux case above-mentioned.

To enble to use your PTT, you have to modify:
#PTT COM1 RTS
Delete "#" and modify to suit your equipment settings.
For example, change "COM1" to "COM2", or "RTS" to "RTS -DTR", etc.

About detail of settings, please read "User-Guide.pdf" file from here: https://github.com/wb2osz/direwolf/blob/master/doc/User-Guide.pdf

After modified your settings, you have to restart "Direwolf".

GRBAlpha - How to use digipeater or DNxD - 07. Settings of soundmodem

I use "Direwolf" because my PC for HAM activity is working on Linux now. But as many people use Windows, I explain the setting of "Soundmodem" for GRBAlpha first.

"Soundmodem" is develped by UZ7HO. I used my Windows10 tablet PC with "Soundmodem" as a TNC for 1200bps uplink or downlink. You must use "High-Speed Soundmodem" for 9600bps of GRBAlpha. You can get the information and download from here: http://uz7.ho.ua/packetradio.htm

I explain here only about the additional settings other than default settings.

For select "G3RUH", choose "Modems" in the "Settings" menu.

You will see "Modems settings" window. Select "FSK G3RUH 9600bd" at "Mode" of "Modem type ch: A" and "Modem type ch: B", and click "Ok".

Then you have to restart High-Speed Soundmodem. You will see "FSK G3RUH 9600bd" on the top.

Additionally, you have to enable "KISS Server Port" for using my application, "GRBAlphaMessenger". I will explain this application later.

For enable it, choose "Devices" in the "Settings" menu.

You will see "Settings" window. Check in the check box on the right of "KISS Server Port 8100". And choose your COM port for PTT, because you can transmit packet data with some tranceivers, like FT-847, only when you activate to PTT port of rear "PKT" connector. In this case, of course, you have to use some PTT adapter for your PC, and connect the adapter to PTT port of your tranceiver.

Then restart High Speed Soundmodem.

GRBAlpha - How to use digipeater or DNxD - 06. RF & AF input level

GRBAlpha satellites has very high transmitting power as 1w according to :

https://www.om3ksi.sk/en/2021/03/18/information-for-radio-amateur-enthusiasts/

When I catch the signal from GRBAlpha, the S meter of my FT-847 with the internal pre-amp enble, indicates up to level 7. You have to get more than level 2 or 3 to decode this GFSK signal, I think. This is in the opposite side of the recent digital communication like FT8, etc. So you may need multi-elements antennas with adequate gain.

On the other side, the input level from the tranceiver to PC should be lower rather than 1200bps. For example, I show you my setting of my PC below.

Please look at the upper right side on this screenshot. You can see a microphone icon and the level. When I listen to 1200bps signals, I set the level a little more than this. Too high input level causes distortion of the signal and misdecoding. I found an uploaded video on Youtube that someone received GRBAlpha signal with RTL-SDR. So many signal sounds were heard but only a little decoded. The sounds from the video was too loud and had much distortion. I think one of the reason for little decoding may be the AF input level.

GRBAlpha - How to use digipeater or DNxD - 05. My antenna, transceiver, and tracking system

For an example, I will introduce my antenna and tranceiver.

My antenna is 15 ele yagi horizontal polarized antenna. 15 ele is more than adequate. I somtimes saw my rig's S meter up to 5. Too strong signal sometimes causes misdecode of software TNC. I will explain about the PC's input and output level later. The reason why I set my antenna as horizontal polarized is that I want to avoid effects from some ground stations like mobile. Of course, the frequency for satellites is not permitted for grounds, but, as you know, some ignore this rule. 

I normally use Yeasu FT-847. It has the output line for 9600bps named as "RX9600" at the "PKT" connector in the rear panel. And I set "PKT RATE" as "9600" in the menu No.23 of FT-847. I sometimes use Icom IC-821 while my FT-847 has some trouble. It also has the output line for 9600bps named "DISK" at the "Accessory" socket in its rea panel. Of course, I set "9600 bps mode" on in the "Set mode with [M/S]".

I use the "Gpredict" for my tracking because I use Linux PC. But I do not control automatically the rotator or rig frequency. I manually control both. I memorize 5 sets of frequencies with 5kHz step for transmitting and receiving just like when you use repeaters. The frequency pairs are like as :(uplink/downlink) 437.015/437.035, 437.020/437.030, 437.025/437.025, 437.030/437.020, 437.035/437.015. According to checking the frequency and direction with Gpredict, I change the memory channel starting from the pair of "437.015/437.035(uplink/downlink)", and I control my rotetor manually. If you control the frequency automatically with your PC, you can perhaps control only downlink frequency. In this case, you can make uplink only around the TCA.

GRBAlpha - How to use digipeater or DNxD - 04. Difference of Signals

I explained a littel about the 9600bps signal sound of GRBAlpha in the former article.

Seeing is believing, I show you here the spectrum figures of the two kinds of sounds in that article. These are screenshots of Audacity on Linux.

The first one is the sound from the "RX9600" output line of rear "PKT" connetctor of my Yaesu FT-847.

The second one is the sound from my handy TRX.

You will find the latter one is deleted low and high area of sound. These deleted parts are very important to decode G3RUH packet. So you need discriminator output on your TRX when you want to decode GRBAlpha signal.

GRBAlpha - How to use digipeater or DNxD - 03. QSL card from Slovakia

When I checked my mail box in front of my house, I found an envelop on which I saw my address in English.

It was QSL card from OM1LD/Robo with whom I had a contact through the DNxD service of GRBAlpha. What a happiness!

But, my QSL card for him, which I have already sent him 2 weeks before, has not reached him yet. What happened? 

GRBAlpha - How to use digipeater or DNxD - 02. Signal sound from GRBAlpha

I think so many HAM have heard the sound of 1200bps packet like APRS.

GRBAlpha uses G3RUH 9600bps packet. The sound is very different from 1200bps packet with your ears. You can download a wav file that I recorded a response from GRBAlpha when I transmitted a DNxD message, from here. When I recorded it, I connected my PC's sound input line to the "RX9600" output line of rear "PKT" connector of my Yaesu FT-847. The data transmitting starts at the half of this wav file. You can hear something different from FM noise.

If your TRX do not have the output for 9600bps, the sound from GRBAlpha may be heard like lower than the former one. You can download a sample wav file that I recorded the signal, that is not of GRBAlpha, received with my handy TRX, from here. The data starts at the same position as above.

You will recognize the difference of these two sounds.

When you want to decode GRBAlpha packet, you must connect your PC to a discriminator output of your TRX. You can decode packet data with the first sample wave file here, but you cannnot do with the second sample. The reason is that the high frequency is cut at the output for voice. The GFSK, like G3RUH, needs wider, for example 5kHz, band width.

GRBAlpha - How to use digipeater or DNxD - 01. GRBAlpha information

For the first setp, you have to know about GRBAlpha.

Main mission: To detect gamma-ray bursts and similar high-energy counterparts of violent astrophysical events at the edges of our Universe with a 75 x 75 x 5 mm CsI(Tl) scintillator detector (adapted from: https://grbalpha.konkoly.hu/)

Callsign: OM9GRB

Launched: March 22, 2021 06:07UTC (15:07JST) ([Japanese] source from: https://www.hiroshima-u.ac.jp/news/63696)

Satellite elements set (as of June 5th, 2022):

GRBALPHA
1 47959U 21022AD 22156.14843487 .00003389 00000+0 22655-3 0 9991
2 47959 97.5317 55.9809 0020956 183.8977 313.6863 15.07462328 64962

Frequency: 437.025MHz +- doppler

Mode: FM Digital GFSK9600bps (G3RUH) 

Protocol: AX.25

Detail information for amateur radio: https://needronix.eu/products/cormorant/hamradio-user-guide

GRBAlpha - How to use digipeater or DNxD - 00. Prologue

I am JI1IZR/Masahiro. I have started HAM since 1975. I am especially interested in the satellite communication of HAM radio in these days.

I have been tracking on XI-IV, a Cubesat built by Tokyo University members, which was launched in 2003. It has been working in the space for 18 years.

I have also taken part in "ARTSAT" project as one of suppoters. The satellites, "INVADER" and "DESPATCH" launched in 2014, were on purpose of "art of satellite in space". It was very interesting and exciting for me that it was the first "ART OF SATELLITE".

Last year,  my HAM friend, JA6PL/Yoshitomo who is very active on Cubesats, asked me how to transmit some command data with software modems to GRBAlpha satellite, that launched in 2021 for a challenge to detect gamma-ray bursts with a Cubesat. 

I have deeply interested in this project. After a lot of trial and error, I succeeded to upload some data and to use digipeater of GRBAlpa. Additionally, after DNxD, Delayed Needronix Digipeater, started to work since April 27, 2022, OM1LD/Robo and I had a contact with earch other through this unique communitcation system.

From here, I will write some suggestion from my trial to let you know and use this interesting system .

OMlLD/Robo is CTO/CEO and Founder of "Needronix" that developed the TRX and other materials of the GRBAlpha satellite. You can see more information about this company from here: