Posts by dm4im

    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.

    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 3600

    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 1500 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.

    Hi,

    i'm testing a Packet Radio setup on 10489.987.000 . Mode is QPSK 3600bd , 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.

    I recorded my own file and transmitted it. The result was such that the audio speed was drastically reduced and there was a broad noise on it. I don't know how to find out the correct properties of the audio file. But then there is a forum for rpitx.

    It is a matter of time until i or someone else finds the solution. BTW: The transmitted file is sampleaudio.wav . First, there is a carrier for a few seconds, then sampleaudio.wav is transmitted.

    Ok, a new test revealed an output power of about 15mW in FM , AM, FREEDV and SSTV.

    And about 0.4mW in SSB. The testfile for SSB obviously is very wide but not well leveled. See attached pictures. Not that bad at all, but still not perfect.

    Hi,

    plug in your Interface for the CAT-connection computer<>radio. Find out what COM-Port number windows assigned to the interface. Start console. Click VIEW > SELECT , check External Radio > OK, console restarts. Now find EXTERNAL RADIO in the left sidebar. Click "?" , then Omni-Rig, select comport number, rig type and baudrate. Click OK. Click UPCONVERTER and set the offset. There is a help. OK.

    Now you should see the frequency in the sidebar. Click PLAY ">" button and the TRACK button. You are ready to go.


    Good luck

    73, Martin


    Doesn't work? Don't hesitate to ask.

    Hi,

    may i point you to https://github.com/F5OEO/rpitx , a software to make the raspberry transmit. I tried it and was surprised.

    The transmitted signal level is high enough on SW, 144 , 432 or 1296 Mhz to drive a booster and then be fed into an upconverter.

    The test-program there provides various modes, It transmits prefabricated pictures or speech from files. I tried SSTV, FREE-DV and SSB.

    The received picture was very good, so was the decoded audio in Free-DV. Also the transmitted .wav-file for SSB was of good quality.

    Setup: Raspberry Pi3 > 70cm Transverter , LZ5HP Upconverter. The level was too low to drive the LZ5HP mdirectly, so i used the 70cm Transverter's 1mW input to provide enough level on 70cm to drive the LZ5HP.

    Unfortunately , there is no way (yet) to transmit audio from a microfone.

    Maybe DL3DCW wants to enhance his satcontrol-Software ? Who needs a pluto when you have a raspberry...


    73, Martin

    Hi Achim,

    i just heated up the dongle with a heat gun, the carrier drifts all over the place and is now back to the position it was before . So at least in my case, the culprit is the dongle. YMMV

    Greetings from your hometown..

    See attached picture, IF-display, yellow arrow. Are we talking about this? This is even there, when i remove power from my lnb, so i suspect

    it is generated in the RTL-dongle. Depending on the accuracy of the 25Mhz reference fed to the lnb, this carrier was above the beacon before i removed power, was there when power was removed and is there below the beacon now that i restored power. It is slowly drifting further down and i am sure it will be above the beacon again when everything has warmed up again. No 10Mhz reference here when i tested it, just a homemade 25mhz reference , rtl-dongle and sdr-console. I have an older screenshot from a while back before the transponder was widened up, the carrier already was there. Will make another screenshot when it has moved to it's "original" position.

    Hi,

    i just tried to feed 10Mhz external to the Pins described in the manual. No joy. The signal on the WB-output is 24.040ish and will not move wether the external source is connected or not. The source delivers 10mW@50Ohm. Connection was: shield to Pin2, 3&4 jumpered, signal to Pin5. I think that's right?


    Found that 10Mhz and 24Mhz are dead on frequency with gps-module in place but no GPS-Antenna connected, but 22Hz high on 10Mhz and 56Hz high on 24Mhz with GPS-satellites found.


    Edit:

    Looks like results are good when no gps-module in place AND unit is jumpered for 25Mhz. WB-out shows 25.0000.000, 10Mhz-out shows 10.000.000Mhz. Firmware is 1.0 . Is there a newer firmware?

    Hi Achim,

    well, if 23.2Hz is a few Hz, so be it. I left my Counter on for 3 weeks now, fed it with a GPS-controlled signal source built by DJ8LC, which i believe is accurate. The counter settled at 10.000,000 Mhz after 2 1/2 weeks now, so i believe it is accurate, too. The radout says 10.000,0232 when connected to the V3d. The 24Mhz reference for the lnb is also off, which results in an offset in the magnitude of 23khz.

    That is a bit more than the "few 100hz" stated in the manual. So if i connect my entire station to these references, which i did, everything is off. Downlink, 70cm Transverter, Upconverter, even the Transmitter itself . Sure, you can get rid of the errors by carefully adjusting the readout on your transmitter to match the tweaked readout on sdr console. Currently, i must set the LO in sdr console to 9360.017.8 to have the psk beacon on 750 and to compensate for the offset happening in the Oscillators for 70cm (102.5Mhz) , LZ5HP (10Mhz),LNB (24Mhz). That somehow is not satisfactory. Am i too picky?

    Hi,

    i watched the Amsat Downconverter V3d with GPS for quite a while and have some trouble with it.

    Firstly, It "crashes" now and then, reboots and starts to work again.

    Secondly, there is a more or less big offset to the desired frequency. This affects the reference for the lnb as well as the 10Mhz output. I'm sure it also affects the 40Mhz output. The description in the Amsat Shop gives an explanation for that, but i wonder why this could not be solved. The Downconverter essentially is a another breed of the Leo Bodnar Reference. Correct me if i'm wrong, but the Leo Bodnar reference is able to output a stable reference, low jitter AND correct frequency without offset.

    So why can't the Amsat Downconverter?

    73, Martin

    Hi,

    du kannst in RECEIVE mit ADD einen zweiten Empfänger einschalten , dieser folgt dem Sender (oder der Sender folgt ihm ).

    Die Empfänger können unabhängig voneinander laut oder stumm geschaltet werden. Damit hast du eine Art RIT, bzw. einen Zweitempfänger, wenn eine Station Split-Betrieb macht.

    Ok, to sort that out: The Receive Bandwith is always 2,4Mhz (or the max. your dongle provides, in my case 2048khz) , your Filterbandwith is always 2.8khz. You only change the Zoom level.

    So what's happening here? sdr-console does not measure the signal alone, rather it does an interpolation of the levels inside the passband?