Posts by DK8KW

    Hi,


    I have made the same observation and was told, that if you reduce the gain to 40 - 50 the signal should disappear. In this case, of course, you need to amplify the LimeSDR Mini externally to compensate for the attenuated signal.


    For my setup (LimeSDR Mini on 50 MHz to feed a BU500) it also worked to calibrate the TX-section of the LimeSDR Mini. in SDR Console, for example, you need to press the TX button and then, on the left side of the pane, press the „TX Calibrate“ button (be careful, you should disconnect the PA before calibrating to avoid damage).



    Best 73


    Holger ‚Geri‘, DK8KW

    Hello group,


    let me give you a short report on my tests with the LimeSDR and FreeDV.


    My setup:


    - SDR Console 3.0.19
    - Windows 10 on an old Q8400 Quad CPU - 2.66 GHz
    - LimeSDR Mini on a separate USB3-Card with power from the computer power supply
    - FreeDv 1.4
    - LimeSDR Mini operates on 50 MHz (replacing a KX3 that I usually use), signal is amplified by 30 dB and fed into a BU500
    - Filter between BU500 and PA to avoid that the LO frequencyof 2350 MHz is accidentally transmitted into space(attenuation @2350 MHz: >90 dB)
    - SG-Labs PA running at about 3.5 Watt output in the shack
    - 15m H-100 cable with a total loss of about 7 dB (including plugs)
    - about 650 mW at the antenna feed (5 1/4 turns helical antenna)
    - dish: Kathrein CAS 180, diameter 1.8m, offset dish
    - reception via Octagon LNB, xtal changed to have output signal on 70cm


    After my first LimeSDR Mini proved to be damaged (not recognized by Windows) I got a replacement which worked right away.


    My general observation is that my computer is far too weak to operate both, SDR Console wih LimeSDR mini transmitting option and FreeDV.


    Reception of FreeDV is not possible due to high frequency variation/jitter. All other digital modes work fine (FT4/8, KGSTV, ect.).


    Reception with a separate laptop and WebSDR works up to FreeDV 1600.


    FreeDV on the mainframe computer will transmit, SDR Console keeps transmitting but the screen will go black and sometimes will not return to its original state, so the program has to be re-settet.


    The LimeSDR Mini has the tendency to freeze, this has also been confirmed by Simon, G4ELI, the author of SDR Console.He has even threatened to stop support for this device.


    Conclusions and solutions:


    - the chain LimeSDR Mini -> 30 dB broadband amplifier -> BU500 seems to be sufficiently linear to transmit FreeDV


    - my computer is absolutely overloaded with the software, so to continue I will need to outsource FreeDV to an external laptop.


    - to enable reception, my LNA will be stabilized with an external, GPS controlled 26 MHz oscillator.


    - if the LimeSDr Mini keeps freezing I will consider abandoning this device and look for another solution.


    By the way: I like the option to transmit waterfall text in the SDR Console. It really helps to announce FreeDV transmissions with the mode used.



    Best 73


    Holger ‚Geri‘, DK8KW

    Hello group,


    Here is a practical example on how effective a helix can work.


    My antenna is a CAS180 from Kathrein, an offset antenna with a width of 180cm and an f/d ratio of around 0,7.


    My LNB is in the focal point of the antenna. The transmitting antenna is a 5 1/4 turn helical antenna just below the LNB (see pictures).


    To show how effective this setup is, I made the following calculation:


    - according to https://www.everythingrf.com/r…ic-reflector-antenna-gain, the theoretical gain is 31,55 dBi (at 70% effectivity!).


    - according to an information that was posted here on the forum a while ago, the EIRP of DL50AMSAT is around 900 Watt.


    - to be as strong as the CW beacon I need to have 623 mW (27,9 dBm) at the feed of the helical antenna.


    - using that power and the theoretical gain (623mW + 31,55 dBi) I get an EIRP of 890 Watt EIRP.


    Conclusions: obviously my setup is very effective; I don’t think I can do any better!



    Vy 73


    Holger ‘Geri’, DK8KW



    @SWL - markro92, good job again, thanks!


    Version 2.0.13 works fine here, using a Q8400 processor @ 2.66 GHz. Once I realized that the BB Gain slider was at "zero" in the beginning, I am now able to quickly synchronize almost every station now. Also, the Transponder Overlay is very helpful.


    Rig here currently: modified Octagon in 1.8m offset dish made by Kathrein, 20m cable, Nooelec RTL stick.



    Best 73


    Holger 'Geri', DK8KW

    Already back in 1984 there was a software called "Dr. DX" for the Commodore C64, simulating an entire shortwave contest with varying band conditions, greyline dx, pile-ups and rare stations showing up and disappearing again throug out the game. There was not even the need for any other ham station to have fun ... ;)



    Vy 73


    Holger 'Geri', DK8KW

    I am asking because stations calling the the dx station will most likely not be listening on their split tx frequency while calling and therefore not hear the LEILA warnings.

    ... the good thing with QO-100 is: a rare dx station will create a pile-up at first, but if you are a little bit patient and give it a few days, the dx station will call you in the end. The amount of stations accessing the satellite (currently) simply is too low to create an hour-lasting pile-up.



    Best 73


    Holger 'Geri', DK8KW

    @SWL - markro92: marcel, thanks for the new version. I have been playing around a little bit with it and it seems to be decoding faster with the new version.


    >Showing Ku-Band Lo/Hi frequencies next to IF frequency.


    What I tried to do is to adjust the frequency offset in the device.ini-file but without success. I use a modified LNB and my L.O. is around 9.500 MHz. I am also missing the readme.txt file that supposidly is explaining on how to set up the parameters.


    How can I adjust the L.O. frequency so that the correct receiving frequency is shows?


    Update: I just played around a little bit and found out, that the frequency in the devices.ini is not the L.O. frequency but the current reception frequency stored with the device. So we have to see what the next version brings ...



    Best 73


    Holger 'Geri', DK8KW

    Hello all,


    For those of you who want to equip the SG-Labs 20 Watt PA with the additional voltage outputs to measure input (DRV) and forward (FWD) power and estimated SWR (REF), here are a few pictures showing that it is an easy task.


    What is needed is just a 2.5mm drill, a tool to cut the M3 thread and steady hands. Wiring is also easy.


    As you can see, I operate the PA with a 12 Volt to 24 Volt up-converter that I found somewhere on the internet. I mounted both devices on the same aluminium heat sink.





    Here is a detailed data sheet of the L4030-034N


    L4030-034N.pdf




    Vy 73


    Holger 'Geri', DK8KW

    SWL-JanV : I can confirm what DB8TF writes. I use 50 MHz as an IF, so the 2350 MHz signal of my older type BU500 had the same problem. I ordered an interdigital filter from ID-Elektronik (I am not very good doing precise mechanical work). The filter has a 90dB notch at the L.O. frequency of 2350 MHz and the problem disappeared.


    Meanwhile (after mechanically damaging the old-type BU500, trying to drill some holes into the housing) I ordered a new one (Version 6) and the problem disappeared. Nevertheless I keep the interdigital filter in the signal path, between the BU500 and my PA, just in case.



    Best 73


    Holger ‚Geri‘, DK8KW

    Hello all,


    I have got my SG Labs 20-Watt-PA yesterday. I like the feature of measuring the input and output power as well as an SWR estimation by measuring a voltage.


    What feedthrough capacitors would you recommend?


    It should be a small diameter feedthrough capacitor and it would be great to have a metric thread, so that it could be directly screwed into the PA housing.



    TNX, best 73


    Holger ‚Geri‘, DK8KW

    Hello all,


    There is a guard band allocated 5 kHz around the beacons, in which no transmissions should be made. Recently I have had a few instances where the SDR-Console lock to the engineering beacon on 10.489.800 MHz was lost due to stations operating too close to the upper beacon.


    It wouldbe nice if you could keep that guard band free from transmissions. Perhaps you can also inform others who are not on this forum.



    Thanks, best 73


    Holger 'Geri', DK8KW

    Hi Lucio,


    I tried my luck yesterday but with my relatively small antenna (Wimo X-quad) I had no luck this time. The sun was too close to the moon and I had a lot of noise to fight. But I agree with you, it was a great adventure and for me it was the first time to receive a signal originating almost 400.000 km away. I was lucky and received the satellite a few times during the past couple of months with my small setup, somewhere in the fields where the man made noise is low. It was a great experience!


    Vy 73


    Holger ‚Geri‘, DK8KW

    I0LYL thanks for the information, Lucio.


    Rohde & Schwarz also have some useful free tools here:


    https://www.rohde-schwarz.com/…ion-note_56280-15492.html


    I like especially their dBm Calculator, which I have installed on my tablet and my smartphone (iOS). It is also available for Windows, Mac, Android, etc.


    I do my complete power level and link budget calculations with it. It simply allows mixed calculations in dBm, mW, W, dB.


    Best 73


    Holger ‚Geri‘, DK8KW



    DF6LO , thanks, Matthias, for your extensive calculations and considerations.


    I wonder if the results of the current so called experimental tool BEMFVDish.exe will be accepted by the BNetzA.


    Well, we shall see! I submitted my sketches and some of the calculations to the BNetzA and didn't get any feedback yet.



    Best 73


    Holger 'Geri', DK8KW

    Hello together,


    I can comfirm what DL5RDI said: the permanent TX-modification is neither necessary for SSB nor for CW. In my view the only valid reason to do this modification is when you want to reduce the power for whatever reason, for example to test low-power (below noise floor) data communication. As the HF-VOX switches only above a certain input power (in the range of 5 dBm), you can further reduce the input power only if you did this modification.


    From my experience I can also confirm that this amplifier can produce around 2 to 3 Watts, not much more. For a brief moment I got about 5 Watt output, but not for long, and not reproducable (unmodified PA).



    Best 73


    Holger ‚Geri‘, DK8KW

    Hello all,


    I agree with what pe1hzg said regarding the possible zone of exposition to radiation. In Germany we have the principle that I have to protect people outside of the „Controllable Range“, which is basically my own property.


    I submitted this sketch as a part of my documentation for the authorities. In order to save a new submission in the future I entered 75 Watt (minus a few dB for cable/plug losses) in my documentation. 75 Watt PEP is the maximum allowed power for class A. currently I only use 750 mW ... :)



    Vy 73


    Holger ‚Geri‘, DK8KW



    DF6LO : In the latest „Watt32“-package that I downloaded from the DARC website there is a program called „BEMFV Dish“, written by DL9KCE. In this software you can calculate the so called „Leistungsflussdichte“ for antennas such as parabolic dishes.


    In most cases the value is way below any critical values. Not the EIRP is important for our cases but a value in Watt per square meter (antenna area). As our antennas point upwards into the sky, even the main radiation is well above people or animals, even if they are fairly close to the antenna.



    Best regards


    Holger ‚Geri‘, DK8KW