QPSK AX.25 Test 2400bd

  • Hi,

    i'm testing a Packet Radio setup on 10489.987.000 . Mode is QPSK 2400bd , SSB . Please feel free to connect. You need:

    Soundmodem.exe by UZ7HO, Easyterm.exe by UZ7HO. Google for it. Feed your sdr-console RX-Audio e.g. via Virtual Audio Cable to soundmodem. Watch for my beacon. If you can see it every 3 minutes, good! There are hints in the beacon text for settings that may work.

    Feed transmit Audio to your Xmitter. Use a AFSK-input rather than the Mic-input if possible. Set center to 1500.

    Good luck.

    73, Martin

    Edit: Extremely important: Do not overload RX with too high level of audio. Keep waterfall in soundmodem dark. A white Waterfall indicates you are overloading it. Also, set your DCD threshold so your system doesn't reply as long your link partner transmits to avoid collisions.

  • Hi, it seems important to set RX-Filter wide, e.g. >3.2 or 3.6kHz . Settings that work for me:

    Soundmodem-Modem settings: Check default.

    Preemphasis All ,

    check non AX.25 Filter.

    Modem type CH A: QPSK 2400

    TX delay depends on your machine, here 100mS work,

    TXTail 10mSec.

    Add RX 0 pairs,

    Add RX shift 0,

    Bits Recovery SINGLE.

    Set your center frequency to 1800 in the Box on the main Page of soundmodem next to the Baudrate for CH. A.

    Set DCD Threshold to a position where the red lamp lights up, when rx a signal. If it doesn't, your machine will TX even when it receives a signal and thus jam the signal.

    In EasyTerm , i set PACLEN to 255.

    Now tune your RX to match the received signal so the red/blue markers are on the received signal. Can you read other stations? Good.

    Now tune your VFO so your transmitted signal appears exactly under the red/blue markers.

    Have fun.

  • ON4KVI and me had a great time this afternoon with QPSK 2400. Seems that 3600 is too wide for some radios. So with 2400bd it worked great. We sent files and messages as well as direct conversation. If you want to connect: The frequency now is 10489.980.000 , center frequency in soundmodem 1800hz. 1500hz seems a bit low for some radios. Use a wide filter for rx. Listen to the beacons, set rx-signal exactly on the markers in the waterfall, then set your tx-signal exactly on the markers in the waterfall. Also, carefully set DCD so it lights up when you receive a signal. If it stays off, your setup will TX while others TX and thus jam the signals. .

    Good luck.

    P.S. we might qsy to the Digital portion of the transponder later.

  • Hello Martin,

    in case of your packet radio mailbox I try to set my frequency to your transmission and it is very heavy.

    Your beacon is not working every 3 minutes but real times every 10 minutes.

    Vy 73 de Uwe, DL6NDK

  • dm4im

    Changed the title of the thread from “QPSK AX.25 Test 3600bd” to “QPSK AX.25 Test 2400bd”.