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Questions tagged [ax.25]

AX.25 is a packet-radio mode; today it is commonly used to send APRS messages. Use this tag for questions which involve configuring AX.25 network software and hardware, or details of the AX.25 protocol and modulation.

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Where should paclen setting come from in Linux ax.25?

On Linux, in the /etc/ax25/axports file, the parameters for an ax.25 interface include: name callsign speed paclen window description When you create a new ax.25 ...
1 vote
1 answer
34 views

nrparms: SIOCADDRT: Inappropriate ioctl for device

I am learning about the Linux amateur radio protocol stack. I'm trying to connect to a remote node using netrom. My axports file looks like: ...
0 votes
1 answer
89 views

Use Direwolf for ax.25 connections w/o kernel support?

Direwolf includes a complete AX.25 implementation, which it uses internally for various sorts of beaconing, etc. Is it possible to use the Direwolf ax.25 stack to connect to another node without using ...
1 vote
1 answer
406 views

AX25 + Reed Solomon : Bit stuffing errors

I'm currently working with a satellite that has AX.25 + Reed Solomon code (truncated RS(255,223)) in GNU Radio. Since there is no frame synchronization pattern, the 0x7e flags are used for frame ...
4 votes
4 answers
14k views

How can I decode an AFSK 1200 baud audio clip? (ISS)

I'm a new ham. The past few days, I've had a few nearby passes of the International Space Station. As it was going overhead, I managed to record what I believe to be 1200 baud AFSK transmissions from ...
5 votes
1 answer
465 views

Where is the Multi-Drop XKISS / BPQKISS spec?

In packet radio, AX.25 is a fairly common layer-2 protocol. Many TNCs implement AX.25 in firmware, so the operator interfaces to the TNC with a serial port, using the TNC's firmware from a shell-like ...
1 vote
2 answers
1k views

GFSK Demodulationsoftware

I need to demodulate and decode a signal.It is transmitted from a satellite using GFSK. The packets are based on AX.25. Could you recommend any out-of-the-box HAM software packages that could do ...
1 vote
2 answers
108 views

Cannot transmit with direwolf ("Audio output start error")

I'm trying to run direwolf (1.6.0) on Fedora 38. I'm using a C-Media USB audio device to interface with the radio: ...
1 vote
2 answers
371 views

ax.25 error shown in direwolf. Fails on channel 8, then 2, then works

Using a Raspberry Pi 3B, Signalink, HT, direwolf and ax25-tools and ax15-apps. All up to date. Clean start. Commands: ...
6 votes
1 answer
672 views

Using Direwolf with multiple radios?

I'd like to play around with ax.25 connections. It seems that if I have more than one radio (operating on different frequencies) that I would want to have multiple ax.25 interfaces. Direwolf creates ...
4 votes
1 answer
181 views

What value goes in the AX.25 PID field if the Layer 3 protocol is not defined in the standard?

I am working on space-ground networking for a Cube Satellite, and one of our candidate Layer 2 protocols is AX.25. We haven't settled on a physical layer, but it's likely to be some form of quadrature-...
7 votes
3 answers
3k views

Is there a difference between AFSK and FSK for AX.25/APRS USE?

APRS uses the AX.25 protocol which assumes the Bell 202 AFSK modulation scheme to generate the actual radio signal. Is there any reason the same signal can't be generated directly with FSK without ...
3 votes
2 answers
317 views

What exactly are Gold sequences and how are they used?

I recently became familiar with the FX.25 protocol extension for AX.25. Within the protocol is what they call a "correlation tag", which is a Gold sequence or Gold code. I've heard that Gold ...
0 votes
2 answers
461 views

Cannot establish AX.25 connection to RMS gateway

I'm trying to establish an AX.25 connection to a nearby RMS gateway (should be within a mile) using a Baofeng BF-F8+ on 2 meters. I'm trying to establish a connection with either RMS Express and UZ7HO ...
1 vote
1 answer
133 views

How do you open ax.25 ports?

I'm trying to follow this tutorial I almost got to the end, about 9:15 was where I got stuck. Right about there, the speaker is about to wrap up- but I get a couple error messages. ...
2 votes
1 answer
69 views

Cancel beacon on AX.25 Linux Stack

I have started playing with HF Packet using a Raspberry Pi running Buster. The AX.25 I have direwolf running a 300 baud modem, use kissattach to create the AX.25 ...
5 votes
1 answer
2k views

AX.25 on macOS (aside from APRS)

I'd like to send raw AX.25 packets from a macOS PC using a KISS TNC (mobilinkd TNC2). I've sent APRS packets with this set up using Xastir, but I'd like to send other information besides just APRS (i....
1 vote
1 answer
521 views

AX.25 protocol packet size

I am new to the world of amateur radio and I am carrying out a university project concerning the communication between satellites and ground stations. My question is: What is the packet size of the AX....