Posts by OE3GBB

  • MY QO100 SETUP

    Hi George,

    I am using Ubuntu 20.04 and Gnuradio 3.8.1 on an i3-5xxx machine. Pluto is GPSDO stabilized and can run duplex over QO-100. I am using the GPIO - relay board for PTT in SDR-Console. Pluto is 192.168.1.7.

    Do you think that equipment will be sufficient?

    73 Gerhard

  • MY QO100 SETUP

    Hi George, that is great news. What do I need to test? I allready do have a Ubuntu computer and a Pluto via ethernet.

    73 de Gerhard OE3GBB

  • Unbricking H.265 encoder box with serial terminal

    Hi Poll,

    I do have the same board and it is also broken now. I have used it with PlutoDVB FW 0303 and I think it was OK for a while. Now I cannot access the http-server of the box, nor get a telnet connection. I also lost the HDMI screen in OBS.
    - I can hook up a TTL RS232/USB, but how to proceed from there?

    - What is the patch for? Is it necessary for working with 0303 FW and how is it done savely?

    73 de Gerhard OE3GBB

  • recommendations for non-standard modes (station identification)

    Hi All,
    According to Austrian regulations all digital modes are allowed, if they do not exceed the bandwith regulations for the frequency band. This includes also experimental modes. But it is necessary to use an open documented digital mode. This can be achieved by using (1) an allready open documented mode, or (2) an experimetal mode. In case (2) it is necessary to show the callsign and mode at the beginning of the transmission (I am using waterfall picture) and give necessary infomation and/or code of this mode at least on a personal internet site.

    73 de Gerhard OE3GBB

  • Increasing noise on LNB during transmission

    Hi all,

    Many thanks for all the contributions.


    Here are the results from my investigations:


    Yes, it is the 5th harmonic problem. I could tune my LNB to that frequency on 12.038 MHz using SDR-Console and could see some TV transponder signals at -115 dBm. But when I transmit at lower power I get the 5th harmonic of my transmission at -80 dBm. When I increase the power I get -45 dBm. So it seems that the activation of the doherty path of the amplifier is making this problem.
    I inserted now a 200W circulator and the situation improved a little bit. I can transmit now 333 kS at beacon level without increasing the noise level.
    I am using bandpass filters for 10W between driver and final amplifier, built for Wifi on 2410 MHz, 27 MHz bandwith, but 10W CW only.
    High power low loss low pass filters could be built according this: https://www.changpuak.ch/elect…mpedance_Lowpass_Coax.php. But I don't have the ability for that kind of high precession work.
    Alternativly those could be built from low loss PCBs with increased copper layer thickness.

    I also do have a WLAN duplexer, but only rated for 20W and I don't want to risc this eather.
    So next will work on optimizing the doherty amplifier to reduce the 5th harmonic.


    73 de Gerhard OE3GBB

  • Increasing noise on LNB during transmission

    Hi Mike,
    that is a very good point. I do not have a SPA for this frequencies, but I will try to tune my LNB to 12025 and see what is there.
    If the 5th harmonic is the problem: This is the first PA I am using without a circulator. So, I also can try ma 200W circulator for 2,4 GHz and maybe this device is acting also as a low pass filter ? How to build a LPF for 200W on 2,4 GHz with minimum losses? I also will try to change the amplifier from Doherty to push-pull A-amp as a last try as maybe the problems arise when the C-part of the amp is activated.
    Will keep you informed.

    73 Gerhard

  • Increasing noise on LNB during transmission

    Hello, I am using a 1,2m offset dish and a POTY feed. Never had that problem before with different amplifers from low power up to 70W. But now I have built an new amplifier using a Doherty transistor pallet module. I am getting increasing noise on the RX (MiniTioune Scan & Tune), if I increase the transmitting power. I don't have this with the diver stage alone, which is also good for 20W DATV. I do have a very sharp band filter (-70 dB) just before the final amplifier. And I cannot see any spurious signal up to 2,9 GHz on the HP spectrum analyser. Shoulders at 75 W output are at 30 dBc. The signal on the WebRX is very clean and I can produce a 16APSK signal at 15 dB without shoulders. I don't have an increase of noise on my nearby 85 cm dish, while I am transmitting with the bigger dish.
    So, what can it be? I don't have oscillations, I don't have a spurious emission on 2,6 GHz. The only difference to the other amplifiers is, that this one is a Doherty type. The operating point of the transistors are correct according to the data sheet and changed only a little bit to increased linearity, but without any change to this noise problem.

    Has anyone had this problem before or has some idea what I could check?

    73 de Gerhard OE3GBB

  • MY QO100 SETUP

    Hi George, Sorry was my mistake. Somehow I thought you are using the LM35 to measure the voltage of some supply. That was a misunderstanding. I have chosen the Arduino Uno as it does have the Ethernet shield for easily sending data over IP. Never heard about the methode you are using by RS232 and a Mikrotic board. Can you send some info about this?

    Reagrds Gerhard

  • MY QO100 SETUP

    Hi George, thank you for this hint. But how do you measure voltages with this LM35?
    I do have an Arduino Uno and a Ethernet Shield. So I will get the LM35s next.

    73 Gerhard

  • What TX amplifier do you plan to use?

    Hallo,
    I have also finshed first tests last week and got about same results. 60W DATV at 30V/10A. Now waiting for a bigger power supply. There is no tuning necessary. About 15 dB of gain at 2406 MHz. Maximum gain is around 2350 MHz, but only 1 -2 dB more. These pallets do have a nice PTT design. There seems to be a temperature switch on the pallet also, but I have not tested it yet. I have used a 4 mm copper plate for heat distribution and a heatsink with blower.
    My pallets seem to be B-ware, but obvisiously have never been used. There are markers on the back pointing maybe to a point with lack of soldering to the copper plate. So far no problem.
    I am now going to construct a PA with two of these pallets to get about 120W DATV out for my small 1,2m dish.
    There was another sale on eBay, but with a pallet for 2500 - 2600 GHz. Also ordered one to see the difference.
    73 de Gerhard OE3GBB

  • POTY vs HELIX

    I can confirm, that I have seen a 3 dB difference between the Rocket-lens and this lens delivered with the POTY on a 0,66 f/D-dish on receive. For NB-usage it will not make a big difference, but for DATV-usage.
    Gerhard

  • MY QO100 SETUP

    George, that's great news. To understand it right: You are transmitting using a Pluto with F5OEO software. The repeater is consisting of another Pluto running Gnuradio on a Linux PC. You are receiving with miniTiouner-Express.
    Would it be possible to use a RaspberryPi for the Gnuradio repeater?
    Please keep me informed about your further developments.
    Regards and 73 de Gerhard

  • What TX amplifier do you plan to use?

    Hello Thomas, Yes I have seen this. But I am confident, that the pallets are OK. They are removed from some amplifiers and so they are used and without any warranty. I have bought 2,4 GHz PA PCBs advertized as scrap in the past and they all work without problems. Will keep you informed, but delivery is proposed at the end of December.