Posts by dm4im

    Well, Eric,

    I suppose the Leo Bodnar Mini Precision GPS Reference runs on USB-power, either from a Computer or a USB-Charger. The larger one has a DC socket. Look at the pictures :…cPath=107&products_id=301

    "Additional Images"

    For the larger one ( not Mini ) the site states: "It does not need any drivers installed or even USB connection. You can use external 12V power supply without USB attached."

    There you have it. Once you have a stable 10MHz clock, you may also derive the 25MHz for your LNB from it.

    Take a look here:

    It shows what you can do if you want to build it yourself. F1CJN took it a bit further by using a OCXO instead of a TCXO, DL4ZAO and DL7UKM made a nice PCB with features like Measurement of Control-Voltage, I did some cosmetics and incorporated a temperature sensor and a bit of code to handle a Si5351 for 25MHz output and some features for the display - like show time with leading zeros etc -that initially weren't there.

    There will be a virtual lecture on the "UKW-TAGUNG" in Weinheim, which will take place online. Find info here:

    There is a Translator-applet in the upper right corner.

    73, Martin


    please specify your query. What are you trying to do?

    If you just intend to use gqrx / sdr-stick, go ahead and do so, there is no problem with that.

    My recommendation for a well working setup (besides DL3DCW's satcontroler) is to hook a raspberry (or any other linux computer) equiped with a rtl-stick into your local network, install rtl-tcp on it, set and forget it.

    Then use your favorite software on a different computer.

    My setup here is a small shuttle pc running as a server for various tasks like mesh-network, recorder for surveillance cameras, cloudserver, pi-hole dns-server etc. And rtl-tcp. It's running 24/7 anyway. I access the stick via network with gqrx or sdr-console, what ever comes to my mind.


    I just read the manual for a Leo Bodnar GPSDO . You hook up the USB-connection for programming it only , then it runs stand-alone. Is that what you refer to and probably didn't quite get?

    73, Martin


    maybe it will run if you just extract the missing and incompatible files from a new image , then copy them to your /boot folder.

    I just learned that there is a new firmware available allowing the pi4 to boot from usb. Maybe your pi4 has a new firmware and wants to boot from usb, but DL3DCW's image isn't ready for that. See

    Chapter8 mentions to copy .dat and .elf files to the boot media.

    Hi, there are no parameters possible via command line. You can start GQRX via script, but you can't hand over any commands to GQRX.

    If your intention is to have a easy-to-access satellite downlink, you might want to check out DJ0ABR's websdr. It provides a browser accessible gui.

    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 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.


    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.

    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.


    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.


    may i point you to , 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.