Posts by dm4im


    the program can run on two different computers and communicate via network , but the installation is the same on both computers. So if DJ0ABR is willing to split the installation into 2 parts, GUI and modem, the gui could install on a win pc without the drivers side by side with the flex software while the modem part could run on a raspberry pi or on a another windows pc. This may also eliminate the hassle with the virtual audio cables.

    73, Martin

    I like contesting a lot. Having said this:

    No antenna to rotate, no propagation to observe, predictable footprint of the signal. Whats the point? It's a repeater, just not fm and not on the ground. Contest is useless there. Maybe that's why it is called "challenge".

    Hi there,

    got it to work on a Xubuntu from 2020 in a virtual machine on my older Linux. It won't compile on the older Linux, because LIBGC is too old. Anyway, just sent some pictures and received them myself.

    Setup: TX: Elecraft K3 in DataMode, 70cm-Transverter, LZ5HP-Transverter.

    RX: Amsat Downconverter -vy old Model- , 2m-Transverter, Kenwood TS-850, USB-Soundcard. Of course this will not be the ultimate setup. Will try to use it on a Raspi4 . With this setup, 6000 8APSK is possible. To me it was important to see how my TX will work in the first place. Now that i know i can transmit, i will refine RX. CU


    a few more thoughts: Your problem will disappear as soon as you hook up your control box to a computer running satellite prediction software and let the program do the job. I'm pretty sure you will do that , because it's a fast paced job to control azimuth, elevation, tx-frequency and rx-frequency by hand while noting your qso-partners callsign, locator, name and report. This is especially true for the ssb satellites and even more when you do cw. Not so much for the fm transponders.

    Let's say , a satellite's AOS (Acquisition of signal - or is it arrival of signal?) is at 300° azimuth, LOS (loss of signal) will be at 120° azimuth. That would be an overhead pass. Your satellite prediction software will rotate to 300° azimuth and to 0° elevation. By the time the satellite rises above horizon, the software will rise your antenna in small steps to the calculated elevation up to 90°. Once reached , it will rotate azimuth by 180° and begin to lower elevation when the rotator has reached 120° azimuth. Never will elevation be greater than 90° (which isn't possible anyway, because when you go beyond 90°, you decrease elevation, not increase it)

    73, Martin


    so what you are trying to say, is, your meter shows the exact elevation of your system, but the rotator elevation physically goes below 'horizon' when the meter has reached 180° and you still push the button? Meaning elevation is less than zero (or more than 180) when you drove your rotator from 0° to 180° and a bit beyond? If that is the case, the mechanical range of your rotator simply is a bit larger than 180° .

    The only rare occasion to elevate the antenna further than 90° is when the satellite passes EXACTLY overhead, meaning you point your antenna to the azimuth where the satellite will show up over the horizon, then rotate elevation ALONE until it disappears below horizon again. All other passes are less than 90°, meaning you elevate your antenna while you also change azimuth. The elevation will never be more than 90° (= straight up) . I think no satellite calculation program will ever calculate an elevation greater than 90°. The meter of the control box to me is stupid. It shows a half circle of 180° on an instrument with 135° (?) range. The same is true for the azimuth, where it shows a 360° full circle on a 135° instrument. But that is another story.

    73, Martin

    Well , the position is indicated by a voltmeter with a scale showing degrees azimuth. It is the operators task to set the minimum voltage to be shown as 0 degrees and the maximum voltage as 360° (180°) . Everything in between might be correct or far off. It depends on the accuracy of the potentiometer , driven by the motor and changing the voltage for the scale. The same is true for the elevation.

    You can do this: Remove the scale from your rotator and make your own. Set the rotator to 0, mark it on the scale. Set the rotator to 45°, mark it on the scale. The more measurements and marks you have, the more accurate is your scale. But again, the 3 dB angle of your antenna seems to be so wide, a few degrees offset won't be noticeable in your receiver.

    Another reason may be a slip in the gear or the potentiomenter.

    73, Martin

    Ok, here my last idea.

    Verify there is power for the GPS-Antenna wether gps antenna is attached or not, just to be sure power is always there.

    Fire up V3D , leave it for 20 minutes. Get a cup of coffee. If it still won't finish the setup routine, remove power, remove gps-module, fire up V3D.

    In either case, determine the frequency @ WB-IN as exact as you can. Now, 10489.750-(390*<your measured frequency>) = <something near or far off 739MHz> .

    Set Pluto to <something near or far off 739>. See Signals?

    73, Martin

    Well, now it's <f-word> up, so it seems.

    I'm running out of ideas. Maybe it's time to bite the bullet and return it to amsat.

    I hope someone from the amsat team chimes in to provide further advice. Anyone?

    Ok, check V3D with a Voltmeter if there is 14V on the NB input and 18V on the WB input. Check the jumpers for the supply voltage.

    [Blocked Image:…DownConverter-V3-JP14.jpg]

    My V3D had the problem that there was a short on one of the F-sockets (soldered in too hot) , this caused the power to fail. Once the short was removed, power was back. Unfortunately, the circuit diagram can no longer be magnified as it was some months ago, so i can't locate the circuit that converts 12V to 14 / 18V . Try to locate it. Measure before and after the circuit ( ithink there are fuses before the circuit, they may be open) . You should find 12V before and 14 / 18V after . If there is a short in one or both f-sockets, the fuses may protect the unit.

    Edit: The Converter is IC3 LNBH26PQR, you should find 12V input @ pin 17 or @ F1 - a fuse- , NB 14V out @ pin 20, WB 18V out @ pin 11 or at the corresponding pins @JP2.

    If there is no voltage, remove the jumpers 14A and 14B and check if there is voltage now. If so, the F-sockets have a short.

    There is a new scalable circuit here:…019/11/SingleDown_V3d.pdf

    Thanks DB2OS for providing it so fast.

    I just talked to Sigi, DG9BFC. He said, the newer Plutos with newer firmware can no longer be modified that easy.

    So depending on your firmware it is possible easily or with tricks only.

    But the easiest way for now is: Use V3D as 25MHz reference for the modified lnb, feed the signal over a device like this:

    Make sure you get one that blocks DC to the outputs and ONLY LET DC GO ONE DIRECTION ---> IN. IN connects to your lnb NB socket feeding 14V. Connect the WB socket directly - bypassing the Splitter - to V3D 's WB & 25MHz socket to feed 18V and 25MHz.

    Now hook your pluto to out 1 of the splitter, your V3D's NB socket to out2, leave out 3 open or put a terminator resistor on it.

    Receive on 740MHz with your Pluto. Leave the bnc on V3d unconnected for now. You can hook up a 2m-radio later if you want.

    Jeeez, why did it take so long to come up with this...

    EDIT: You have a bias Tee, so: Pluto -> bias Tee-> NB of your lnb.

    V3D WB IN & 25MHz out -> WB out & 25MHz in of your lnb. Set Pluto to 740MHz. Should work.

    somewhere around 146 MHz there was a very high peak. But It appeared out of the blue. It was suddelnly in the middle of the screen instead of shifting in with 100 KHz steps as i was sweeping. Do you ave any idea what might cause this or if its related to the problems I have?

    Well, maybe it is generated somewhere in your Receiver chain, things like this happen.

    Your gqrx should look like this: lower beacon , psk-beacon, upper beacon. The rest are signals from stations talking. The beacons are always there, even when no one is using the satellite.

    Yes, I am not ... yet. :D

    Well, nobody is perfect...

    Umm.... The pluto can receive on 144MHz? Unless you modified it, it starts at about 340MHz? So set your V3D to 435,5 or 439,5Mhz output and try again...

    Could that be the problem?

    V3D Manual says:

    Für Stellung 8 und 9 (70cm) muss das standardmäßig eingebaute 2m Filter auf der Platine mit einem möglichst kurzen Draht überbrückt werden.

    You can modify the pluto firmware to make it receive down to 60MHz i think.

    Ohne Gewähr:

    This might be outdated.

    A few more hints: A unmodified lnb may be far off. So set your gqrx bandwith 2MHz wide , just to be sure to find the satellite. The lower telegraphy-beacon should be on 739.5 , the upper beacon about 500kHz higher. Right in the middle between them, there is the psk-beacon. While you receive the satellite, you might want to reposition your dish for optimum signal-to-noise ratio. Don't forget the skew angle, it should be about 13 degrees.

    Alright, it seems you are not a ham-radio operator, otherwise you'd knew what a handheld or walkie talkie is.

    So you can not transmit on 437MHz to check the lnb.

    Ok, 40ish MHz an 25ish MHz is good! Means the TCXO in V3D is working and you have output, just not disciplined by GPS.

    Now, who modified the LNB? Was it someone who can check it ?

    Feeding the UNMODIFIED lnb with 24(25) MHz external will not work. It will use it's internal crystal.

    But you should see signals on 144MHz IF YOU jumper V3D to 25MHz and listen on 144MHz. The output of the unmod lnb is 739 MHz and will be converted to 144MHz if V3D is set to 25MHz , otherwise , when it is set for 24MHz it expects 1129MHz to convert it to 144MHz, so if you still feed in 739MHz, the output WILL NOT BE 144MHz. Here's why: Modern lnb's use a 25MHz crystal, multiply the frequency by 390 to get 9750MHz . 10490MHz-9750=740MHz . In order to receive the Amateur TV-Transponder with consumer electronics satellite receivers, which cannot receive 740MHz, one must use a frequency they can handle. So if you feed 24MHz instead of 25, the result is 10490-9360 = 1130MHz, which they can handle. So i think you are close to receiving with your unmodified lnb->V3D->Pluto on 144MHz if you set V3D to 25MHz. Try it. Just don't bridge NB IN and WB out, but hook the unmod lnb to NB IN. If that works, the culprit might be the modified lnb. So once you have a working modified lnb, next step is to find out why gps doesn't work.

    GPS Antenna: Any that can handle the voltage from V3D should do, there are many available ranging from just below 3 V to just above 5V.

    Modified lnb: Is it known to work properly (like give it to someone to test in a different setup) , do you have access to a 24(25)MHz source? Do you have a frequency counter or shortwave receiver to verify 10MHz at the 10MHz output, 40MHz respectively and 24MHz at the WB-connector of V3D (careful, there is 18V , pull the jumper before that). Do not measure at the gps-module, measure at the dedicated outputs. IIRC you can use V3D witht the gps removed , you then should also find those frequencies, just maybe a little offset. I'm still convinced that you loose the gps-satellites. BTW, it takes a couple of minutes for V3D to provide all outputs after it was powered up and has gps signals.

    Can you transmit with a handheld on 437.075MHz in front of the lnb to see the 24th harmonic on 10490,400?

    How did you receive 739 MHz on gqrx? What was the setup? Was it different from the setup when you received on 144MHz? Just the lnb or did you exchange more components? Is there a short in the plastic bnc output->144MHz? When you use the unmodified lnb instead of the modified one, does the combo lnb -> V3D -> sdr(pluto?? or what?) ->gqrx work?

    So if the display says "Syslock : wait" the GPS connection is lost?

    I think so. Did you reposition your GPS antenna? Where is your antenna located? Indoors? Can you try a different GPS antenna? At my qth, if i put the antenna behind the window and shutter, gps-reception now and then drops to zero. If i put the antenna outside just on the other side of the window and shutter i have 7 satellites minimum.

    In my version of the Down Converter this signal has to be provided by an external source, right?

    Yes. I'm not sure about the level. Remove the GPS Module , put a jumper across 3 & 4, feed 10MHz to 5. The frequency schould be extremely accurate, because it will be multiplied to provide 24 (25) MHz and the LNB will multiply it factor 390 for 9360 (9750) MHz, so even a small deviation will result in an offset. BTW, your LNB multiplies by 390, right? If the multiplier is different, we need to recalculate.

    Please name the brand and model of your lnb.

    And for the GPS module: Could I power the module with 3.3 V and measure the frequency output at pin 4?

    You might, but what for? You can check for 10MHz while it is built in, no need to pull it out.

    You said you successfully use an unmodified lnb. So the dish is pointing to the sat. One error eliminated. But: How do you feed the reference from V3D to your modified lnb? The reference is on the wideband connector only, not on the NB-Connector. So if your lnb shares output and reference input on a single connector, you need to rethink the setup.


    in Post #200 , your converter is a silicon labs 2102, in post #206 it's a prolific. Are you sure you have checked the prolific with sdr-console or did you only verify that the silicon labs is working? Try the silicon labs under linux as well as the prolific under windows just to be sure.