Amateur Radio Stack Exchange
Amateur Radio Stack Exchange

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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15 questions
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3 answers

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 going through the audio frequencies? My reading…
jgalak
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6
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1 answer

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 a /tmp/kisstnc symlink to the KISS pty device,…
larsks
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5
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1 answer

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.e. put my own information into the AX.25…
watkipet
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5
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1 answer

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 interface. Many TNCs also allow a "raw mode"…
Jacob
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4
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4 answers

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 it (AX.25) - from it's 145.825MHz Packet Radio…
Brad
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4
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1 answer

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-encoded PSK. If we were using Cubesat Space…
VE9PEG
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3
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2 answers

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 sequences are used when there are multiple signals using…
Steve Mucci
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2
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1 answer

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 port and then use axlisten and axcall for the packet work. The problem: I created a…
Joshua
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1
vote
2 answers

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 either GFSK demodulation or AX.25 decoding?
Moses Browne Mwakyanjala
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1
vote
2 answers

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: Bus 003 Device 008: ID 0d8c:0014 C-Media Electronics, Inc. Audio Adapter (Unitek Y-247A) I can successfully aplay sounds to that…
larsks
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1
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1 answer

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.25 protocol ?? Or, if there is no constant size,…
Federico
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1
vote
1 answer

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. 2020/8/10 22:22:33 HTTP service (0.0.0.0:5000) 2020/08/10 22/22/33…
BJsgoodlife
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1
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3 answers

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: sudo direwolf -p sudo kissattach /tmp/kisstnc wl2k obtain assignment to ax0, then beacon -s wl2k "testing" first attempt -…
ASzy
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1
vote
1 answer

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 delimiting followed by the bit de-stuffing. To make…
Moses Browne Mwakyanjala
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0
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2 answers

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 sound modem on Windows or with ax25-tools axcall…
penguin359
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