Posts by HB9EKO

    The VOX is always active. As long as you just use SSB, it's not necessary to do anything with the PTT.

    However, at CW speeds higher than 15 WPM or so, my setup tends to "eat" the first dot (no dashes), i.e. either the PA's or the transverter's VOX doesn't react fast enough. If you plan to use CW more than occasionally, I'd recommend to wire the PTT.

    73 Jens

    Hi Enzo,

    I have locked my LNB to a GPSDO. When I switch everything on and the GPSDO has not been running for a week or so, I have a similar effect for a few seconds before the GPSDO is locked to the satellites. (The waterfall looks similar) Thus, to me it looks like an unstable reference frequency.

    73 Jens HB9EKO



    any tested models for buck converters as I am afraid of high noise or is that something not concern?

    I use a cheap Chinese buck converter to supply my SG-Lab PA…042311.0.0.27424c4dUd5DT4

    No issue with noise from the DC-DC converter, at least not in the DL receive frequency range.issues with noise so far. Output voltage, and thus output power of the PA can easily be adjusted.

    My setup: I have my SG-lab transverter, PA and DX-Patrol bias tee in a outdoor enclosure close to the dish, all on a common power supply. From that box, 15m RF cable to a RTL-SDR stick (for DL) and FT-817 (for UL), 8m cable to the 12V power supply,

    73 Jens, HB9EKO

    Now GQRX as master and the FT-817 as slave for the sync is still on the wishlist. So the next step is probably understanding the code of this tool...

    Easier than expected. I found out that without modifying anything in the code, I can simply swap the CAT information of RX and TX, as well as the start frequency entries. This makes the FT-817 follow the RX frequency of GQRX. Done some cosmetics by replacing "TX" with "Master" and "RX" with "Follower" and changed the default entries accordingly. Now the tool does what I expect it to do, The "Follower" follows the "Master" regardless what is TX and what is RX.

    73 Jens HB9EKO


    as promised, I would like to provide an update:

    Now I just have to find the time to continue .... / Jetzt muss ich nur noch die Zeit finden, weiter daran zu arbeiten....

    i finally found some time to follow up on this subject.

    In a first attempt, I tried to run Satcontrol on my Shack PC instead of a Raspberry Pi. Unfortunately, I did not manage to run it on my Kubuntu 20.04. Python 2 is not available by default for this Distri, and my attempts to install Python 2 with instructions from the web did not result in Satcontrol and Python 2 cooperating with each other. Porting it from Python 2 to Python 3 turned out to be something major, so I put this on hold for the moment.

    I spent a rainy weekend learning some python basics and understanding how I could code what I want, but then I realized it will take me much more time to learn how to use libraries to create a GUI for the programme and hamlib to read and write the frequencies from GQRX and the FT-817. So I put this on hold, too.

    Shortly before ordering the mentioned issue of Funkamateur, I found a tool called "QTrackUplink" : and decided to give it a try. After spending a couple of hours setting up QT Creator and understanding how to use it, I managed to compile the source code on my PC and got it working.

    This is almost what I was looking for. I can tune UL and DL with a basic offset. After that, the RX frequency in GQRX follows the TX frequency when I change it at the FT-817.

    I'm happy with this for the time being. Now GQRX as master and the FT-817 as slave for the sync is still on the wishlist. So the next step is probably understanding the code of this tool...

    73 Jens, HB9EKO

    The Python program you can download here:

    Maybe that on your system some additional packages need to be installed. On the complete Raspberry image everything is already prepared.

    Thanks a lot, I will give it a try

    Hallo Jens, ergänzende Informationen:

    • Für den DL wird ein rtl-Dongle verwendet; ich verwende einen mit TXCO.
    • Für den UL wird über einen USB/Seriell-Wandler ein geeigneter Transceiver angesteuert. Einzige Bedingung: der Transceiver muß in dem Programm rigctld (aus der Hamlib) gelistet sein.

    Besten Dank, dann weiss ich, dass sich bei Bedarf eine Heftbestellung lohnt.

    Now I just have to find the time to continue .... / Jetzt muss ich nur noch die Zeit finden, weiter daran zu arbeiten....

    73 Jens HB9EKO

    Hi there,

    thank you for your replies / Danke für Eure Antworten.

    It looks to me like there is no "out of the box" solution for my specific setup, but I got some good inputs that might help me to get towards what I'm looking for, provided I find the time.

    Es schaut so aus, als ob es keine fertige Lösung für mein spezielles Setup gäbe, aber mit Euren Hinweisen habe ich ein paar gute Ansatzpunkte wie ich weitermachen kann, wenn ich die nötige Zeit dafür finde.

    Not really adressing your questions, but i wrote some small Python program to 'organise' the CAT control of the FT-817. See…ster/ for more info.

    Maybe this helps you in some direction.

    vy 73 de Johan, PA3ANG

    Hi Johan,

    This looks similar to what I'm looking for, I would have to modify this script to read the RX frequency from GQRX rather than a FT-817.

    I have limited programming skills, since I wrote my last programs decades ago in Turbo Pascal. In the "External applications" section of, I found some tools like gqrx-hamlib that also go into that direction, however I failed to get it running on my machine so far.
    Maybe it's a sign that I should invest the time and learn some python and/or go deeper into details with my Linux setup? :/

    in Heft 12/19 der Zeitschrift "Funkamateur" ist genau dieses Problem behandelt worden von DG7BBP unter dem Titel "Sende-Empfangs-Synchronisierung per Software beim QO-100-Betrieb".

    Dieses Lösung läuft bei mir auf einem RaspberryPi 3 stabil.

    vy73 de Hermann-Josef

    Hallo Hermann,

    kannst Du mir ein paar Details nennen? Setzt diese Lösung ebenfalls einen RTL-SDR Stick für den DL und einen externen TRX für den UL voraus? Wenn ich damit weiter komme würde ich das Heft bestellen.

    Maybe this will work for you: SAT Controller SDR Nano

    Hi Frank,

    I am sure it would work, but since my PC in the shack is already connected to the FT-817 and gqrx is perfectly working, I would like to avoid setting up a separate hardware only for SAT control.

    I would appreciate if I could use the software/sourcecode. However, reading other related threads in this forum, I understand that Satcontrol is only available as a RasPI image and not generically for installation on any Linux machine. You certainly have your reasons for distributing the solution only in this way.

    Thanks for all the hints, I will update this thread when I make some progress. / Danke für all die Hinweise, ich werde diesen Thread aktualisieren, wenn ich Fortschritte mache.

    73 Jens HB9EKO

    Hi there,

    has anybody successfully managed to synchronise the UL and DL frequencies of a RTS-SDR and a FT-817 with Hamlib on Linux?

    On the RX side with my RTL-SDR, I can use GQRX or CubicSDR which are both fine.

    It gets tricky when I try to hook the software up with my FT-817 CAT control:

    In GQRX, there are some python scripts available which are supposed to link GQRX with hamlib. I did not manage to install them on my machine running Kubuntu 20.04, since they require an older version of QT.

    CubicSDR also looks quite nice and it has some TRX control functions included. However, they seem to be made to use CubicSDR for a panadapter with a TRX. Proper documentation does not seem to exist, and when playing a bit with the respective functions, I did not manage to set my TX frequency on 70cm to anything without CubicSDR setting the same 70cm frequency on the RTLSDR-stick :-(

    Has anybody got an idea how to approach this subject with either GQRX or CubicSDR??

    73 Jens HB9EKO

    Hi Nick,

    being active in SOTA myself, I know very well how it feels like to struggle for the 4 QSOs. I will watch out for your activations to chase you. I don't have a portable setup for QO-100, but will gladly chase you if I'm at home during your activations. Having said that, this is more likely on the weekends or after work, even on the days when I can do home office, i can't always be QRV.

    73 Jens HB9EKO

    A cheap Newgen.RTL.2832SDR and the way more expensive SDRplay RSPdx are showing no difference in SNR on the NB&WB.

    Checked that some weeks ago.

    Thanks a lot, that's what I was interested in.

    With regards to the SNR. the crucial factor is the size of the dish and - to a smaller amount - the noisefigure of the LNB. The output of the LNB is way above the reception threshold of all SDRs. Goonhilly WebSDR runs a 1.3m dish.

    Thanks Jean, that makes the audible difference plausible. Looks like an increase of dish size is the best option, if feasible.

    by the way SDRconsole is a fantastic sortware and the audio is better compared with the classic receiver-converter approach.

    Hi Alex, thanks for the info. I am running GQRX native on Linux, and SDRconsole in a Windows VM. I have not encountered major difference in audio quality between the two programmes. (maybe I should try to play with filter settings). So it looks like it's not worth investing in a downconverter. I was considering a conversion to 28 or 50 MHz in order to make use of the DSP filtering capabilities of my FT-891, but rather stick to what I've got.

    Thanks for all the info, and hope to talk to you on the sat soon.

    73 Jens, HB9EKO

    Hi there,

    I have optimised my QO-100 setup to a degree where I am happy with it for the time being. My signal with 2W into a 70cm dish is about 6dB below beacon level and fine fo QSOs in CW and SSB.

    While I'm enjoying QSOs with that setup, I'm already thinking ahead for the next possible improvements: The S/N of my setup with a cheap Chinese RTL-SDR stick is obviously not as good as the various WEB SDRs, i.e. signals which are barely audible in my setup are better on the WEB SDRs. While my possibilities to increase the dish size are a bit limited, I wonder whether there are other possible improvements.

    In order to get a feeling if it's worth investing in that part of the RX chain: Has anybody made a performance comparison between different SDR receivers? Is it worth investing in a more sophisticated SDR RX, to have a better reception than the Chinese RTL-SDR clone? Are there other SDR X with a significantly better performance? How does the RTL-SDR perform in comparison with a downconverter and a conventional HF or VHF RX?

    73 Jens HB9EKO

    Hi Luc,

    the cable will always be a compromise between attenuation and minimum bending radius of the cable, i.e. the cable type depends on your possible mechanical setup.

    I use Aircell 5 which has a minimum bending radius of 25 mm (for bending once, i.e. a fixed dinstallation) but an attenuation of 0.5 dB/m ( less than 3dB for your setup).

    If you can manage to install a cable with a bending radius of 40mm, then Ecoflex10 would have approx. half the attenuation of Aircell 5.

    If you go for a even thicker cable, let's say Ecoflex15, you could get the attenuation down to 0.16 dB/m, but the minimum bending radius is 70mm, which is pretty unhandy.

    What s your exact setup? Do you really need to have that length of cable between PA and POTY, or could you place the PA closer to the antenna and run a longer cable between the PA and the TRX/Transverter? If the output of the TRX/transverter exceeds the minimum required input power of the PA, it might be better to put the cable loss in your link budget there.

    I have connected my feed to a transverter with 0.5m of Aircell 5, and then run 5m RG58 from my 70cm TRX to the transverter. Thus I have most of the output power at the antenna, RF cable diameter is 5mm everywhere, the cables are cheap and flexible for my semi-permanent setup.

    73 Jens HB9EKO

    It should be OK, even though it is quite an old CPU from around 2012, without hyper-threading but with 4 cores. Had it been an early i3 with dual cores and limited performance it may have struggled. Especially if you had been looking in a wide bandwidth (some MHz) with a high res screen to update. There should be a CPU and GPU load indication at the bottom of the screen, as long as it's well below 100% you are not limited by CPU.

    Pluto bandwidth rates with USB are not great and console does tend to crash if the connection to the SDR fails on it. USB lead, USB power, all things to check. If its more stable at 900kHz try 750kHz, 550kHz etc. That will help work out what is causing the crashes. There is also a logfile under tools. Another thing that causes crashes is where the Pluto reboots because it detects incorrectly that the power to it has changed. This is very common if you have an external antenna connected which is grounded. There is a mod to fix this.


    Hi Mike,

    as I mentioned, I use a mobile i3 CPU even a generation earlier, and it's definitely not the limiting factor.

    I can confirm that the USB connection does cause crashes of SDR console. My Chinese RTL-SDR stick is a bit wobbly in the USB port in the laptop, and I have to be careful not to touch it accidentally. It helped to use a short USB extension cable to get the SDR stock out of the way.

    73 Jens, HB9EKO

    On an old laptop (i3 2310m, 8GB RAM), I have approx. 40% CPU load. (BW 1 MHz) when running SDR console without anything else.

    73 Jens HB9EKO


    This weekend, i had a close look at my setup again, and checked the signal path from the focal point to QO-100 +/- 10°. I then figured that there is not only the steel structure but also the balcony railing in the way. :-(

    I replaced the attenuator-style jumper from the transverter to the feed with a piece of Aircell 5. Then I started looking for a "sweet spot", shifted the dish around on the balcony with an eye on the signal strength of my own TX signal via the transponder, and found around 5-6dB. :-)

    CW QSOs are not a problem at all anymore. I even made a few successful SSB QSOs, QSO partners confirmed that my signal was weak but clearly audible. The beamwidth is now probably limited by the balcony railing on the bottom, and the upper balcony on the top. The steel pole is about 1.5m in front of the focal point. During a QSO with someone with the same TX power and dish size, I noticed around 4 dB difference in signal strength. That's apparently what disappears in the steel pillar, which is now 11-12 wavelengths from the focal point in TX direction.

    Thanks for all the hints, now I can experiment with improvements to my setup for better SSB QSOs rather than struggling to communicate at all. Lessons learnt: an obstacle in the signal path does not neccessarily make QO100 operation impossible.

    Vy 73 de Jens, HB9EKO.


    G0MJW  DD4YR the picture doesn't clearly show the real direction of the antenna. When I started experimenting. I considered the visibility of the satellite already (see the thread DRO LNB for testing RX signal levels? )

    I have LOS and a reasonable RX quality (maybe not the last possible dB), that's why I got optimistic and started investing into equipment.

    I was aware from the beginning that the Fresnel zone is not clear, but there's nothing I can do about the position of the satellite, my balcony and the fact that I have to stay as stealth as possible. So now that I did my initial investment, I will just investigate further until it works. That's what ham radio is all about, isn't it? :-)

    DH2VA Looking at the setup now, I think it will be easiest to remove the concrete plate fom the bottom of the dish stand, put a box inthe corner of the balcony and move the dish temporarlily across the balcony railing. Then I have numbers in dB regarding the steel pole, and know where I am. I also hope that the situation at the borders normalize again, then it will be easier to buy components just for experimenting.

    I was hoping that someone else in the Forum might have experience with similar issues already, but it looks like I'm the first one, so I'll keep on experimenting. The results will hopefully support other OMs in similar situations.

    73 de Jens, HB9EKO

    DD0KP For that price I agree. Here they cost much more. I found the antenna on Ebay. The seller doesn't ship to Switzerland, and he can't be contacted with the "Contact Seller" function on Ebay. Looks like I have to put that on hold until I can get across the border to my parcel handling service :-(. I don't want to spend half the price of let's say the SG Lab PA more for try and error.

    73 Jens HB9EKO