Posts by dm4im

    The Satellite Experimenters Handbook, 1984, says we are dealing with Faraday Rotation, where linearly polarized signals from a Mode A satellite (AO-7 IS a Mode A sat) slowly rotate when they pass through the ionosphere, most noticable on 29MHz as fading. The polarization now is elliptical. A circular polarized rx-antenna will compensate this, but will not cure all fading , since the the gain pattern of the antenna in the spacecraft constantly changes as it spins.

    So, i think it is best to switch from RHCP to LHCP and back while observing the signal.

    You may ask why do i care about this? Well, after all it is less an experiment for reception of a Mode A satellite, but more an experiment for diversity receive on 12 & 10m. I will focus on that and put proper reception of AO-7 very low on my to-do list.

    But if polarization was known beforehand, I sure had set it correct. Will i ever bother switching from RHCP to LHCP for AO-7, i don't know.


    Thanks for reading

    73, Martin

    Thomas, thanks for the reply, BUT

    i'm not asking if a dipole will do. I know it will, i've been using radio sputniks when they were operational.

    Now that i have this circular polarized antenna, i want to set the proper sense of rotation to benefit from the circular polarization it has by design. If i set the wrong rotation, losses will be higher than with a linear antenna. If i set the correct rotation, performance will be better than with a linear antenna. It's a matter of flipping coax shield and core. I just have to do it right once.


    73, Martin

    My 2 Cents on this:

    You are trying to create a workaround because your OTG USB Network device doesn't work as you want it to work.

    But this creates even bigger problems. Get your Network device working and you'll be fine.


    If you really want to deal with problems: You may need to route the audio output from your teamviewer to the audio input of sdr-console via virtual audio cables. I'm not sure if this will work. Good luck.

    73, Martin

    Dear Satellite enthusiasts,

    i recently read in cq/dl ham magazine about a circular polarized (CP), omni directional cross-dipole (aka turnstile) covering 12m and 10m and everything in between.

    Looking at the frequency range of 5 MHz, I was very sceptical. But with all the required hardware handy, i gave it a try. No tinkering at all, just built per the article, my antenna analyzer confirmed a good , flat match over the entire range from 24.9 to 29.7 Mhz with a perfect match somewhere around 26.7MHz. This is a contradiction to the statement in ROTHAMMEL antenna book, where turnstile antennas are described as narrow band antennas. Anyway, with the dimensions given in cq/dl, it is not narrow band at all.


    Polarization from sky wave signals (dx) never are pure V or H, but they sure are not CP. Hence the sense of rotation the antenna is constructed for is not important. There should be some advantage over a V or H linear polarised antenna and i can live with the loss i will have from pure H or V signals coming in via ground wave.


    But if i want to receive AO-7, what polarization should i set the antenna to? Is it RHCP or LHCP - just connect the delay line correctly, no big deal. Do i need to switch polarization? Spin modulation comes to mind. Found nothing meaningful (to me) in the ARRL satellite experimenters book, but honestly , i did not dig too deep.

    Anyone?

    Now calculating the dimensions for the same antenna, but for 15m - 17m.


    73, Martin

    OTOH, if you put it in a box but the cw beacon still whines even after you allowed the downconverter to settle, there might be a problem other than air draft. Can you make a screen video of your sdr software showing the cw beacon so we can see and hear what's going on? Please also list all equipment involved, like dish-size, lnb, receiver.

    As a reference how it should sound (well, I think it should sound like this) , see https://www.<mycall>.de/uncategorized/qo-100-beacon-snr/

    and https://www.<mycall>.de/wp-content/uploads/2021/10/qo-100_beacon-2021-10-04_10.12.54.mp4

    Replace <mycall>.


    BTW, place the box where vibrations are minimal, preferably on a piece of foam. I once operated it on my operator desk and even bumps from your fist on the desk can be heard as small frequency jumps when you listen to the cw beacon.

    Remember, a frequency variation of 10 milliHertz results in a 3.9Hz shift after multiplied by 390. You will hear that. The crystal in the tcxo after all is a mechanical device. It wants to sit still (and flat) for optimal work.



    73, Martin

    The reason is simple: Air draft will have an impact on the frequency any (tc/oc)xo delivers. The comparator circuit senses the gps generated frequency differs from the frequency generated by the xo , so tries to provide the correct control voltage to compensate for this.

    The xo overshoots slightly, the control voltage will be corrected and so on, until the xo frequency is the same as the gps control frequency. This is a slow process and being slow is good, otherwise you'd experience a lot of jitter.

    You can minimize this when you put the board in an enclosure (plus put some foam on the tcxo) . Or use a ocxo which already is some sort of tcxo but with an air tight enclosure and heater built in. But even then i'd not skimp on an enclosure.

    And please remember, the gps only is there for the long term accuracy, while the tcxo is there for the short term stabilty. It takes a while for the system to settle. Hours at least, days for even better accuracy. Air draft will mess this up and the play starts again.


    73, Martin

    Geert,

    this happens when you close all receivers prior to shutting down SC (sdr console). If you shut it down with a receiver in USB mode still running, it will start with the last frequency, mode etc. when you hit the "Start" icon.


    IIRC you can set a checkmark "automatically run the last receiver when SC loads, no need to hit START" somewhere in the guts of SC. BUT if there was no last receiver when you shut down SC, it can't come up with one.


    So maybe you just need to loose the habit of stopping all receivers before leaving SC.


    Does that help?

    73, Martin

    Die Version im Video ist 0.89. Ist die schon irgendwo veröffentlicht?

    73!


    P.S. Der cw-skimmer funktioniert jetzt, dafür geht das Cluster im Moment nicht.

    Wenn Firefox schon installiert war, aber nicht der Standardbrowser ist:

    Gehe zu den Einstellungen von Firefox:


    73, Martin

    Edit : Link removed, no newer participants over a longer period

    Please do NOT participate if the program works with no errors but you can not decode data. This is a different cause.

    Please set a green checkmark for the OS you use if hsmodem runs without issues.

    Set a yellow mark if it runs without crash but displays errors

    Set a red mark if it crashes or doesn't run at all.


    You can edit your choices any time.


    Thank you

    I did a quick research on "recvfrom error: 10040" .

    Found: This usually means that the buffer you provided to recvfrom() was smaller than the incoming datagram.


    So maybe a issue the author can fix easily just by providing a bigger buffer .

    I don't think this will crash the program, but data will be lost.


    I think the buffer size is defined in udp.cpp in this section:


    Code
     RXCFG rxcfg;
        memcpy((uint8_t *)(&rxcfg), (uint8_t *)param, sizeof(RXCFG));
            int recvlen;
        const int maxUDPpacketsize = 2048;
            char rxbuf[maxUDPpacketsize];
            struct sockaddr_in fromSock;
            fromlen = sizeof(struct sockaddr_in);
            while(*rxcfg.keeprunning)
            {
            recvlen = recvfrom(*rxcfg.sock, rxbuf, maxUDPpacketsize, 0, (struct sockaddr *)&fromSock, &fromlen);

    So if you have this issue , replace 2048 with, say 4096 , recompile and see if the message is gone


    But I may be completely wrong and maxUDPpacketsize must decrease instead.


    73, Martin






    With Chromium set as default browser , the qo100info.html will work ok when opened from the Filebrowser as well as when clicked on "Open received HTML file" within hsmodem . This also applies to Slimjet as default browser. Maybe a firefox issue?


    73, Martin

    Is there a debug mode we can start to "see" what causes the modem crash? Found nothing in the wiki.

    DM4DS Can you start it from the command line in the Terminal under windows10?

    Edit: Sorry, just noticed that a DOS BOX opens and shows status messages under windows as well.


    Some Observations when running under Linux:

    hsmodem freezes, when i try to open Firefox by clicking on "Open received HTML file".


    Does not freeze when i go to the folder containing the html file, right click and choose Firefox to open. But will not show any data in the browser. Does not even display "Offline" in red.


    Does not show errors in the Terminal in both cases.


    Works normal when i go to the folder containing the html file, right click and choose Chromium or Slimjet (a fork of Firefox) to open. Will show data in the browser. Displays "OFFLINE " in red and will change to "CONNECTED to local HSmodem" in a second or two.


    I will try later to set the default browser to either Chromium or slimjet and click "Open received html file " to see what happens.

    Will report ASAP.


    73, Martin

    EA2ARU Please more info. Is it Windows or Linux?


    The beauty of running this under Linux is: There is no virtual audio cable.

    See the picture , it is gqrx and hsmodem running on a ubuntu ( Lubuntu , that is). The audio device gqrx delivers audio to is the soundcard, the capture device for hsmodem is MONITOR output of the soundcard. 73, Martin


    EA2ARU There is no Trick. Connect the input of your soundcard to IC9700

    ACC1 , Pin 2 (GND) Pin 5 (Signal).

    OR to Speaker out (not recommended, but will work)

    OR to headphone out (not recommended, but will work)

    Goto hsmodem SETUP, set RX to your soundcard input. Tune your IC9700 RX-frequency until you see the constellation like in post #59 . Follow the instructions in post #59.

    Also, carefully read instructions in your manual about the speaker configuration in chapter [EXT-SP MAIN / EXT-SP SUB] if you connect to your speaker output.

    EDIT: Additionally, check the manual provided by Amsat (see next post) if you want to use USB SOUND features for RX and TX with ICOM Transceivers.


    73, Martin