Posts by DK8KW

    Hello all,

    here are some sample measurments from my rig:

    - Pluto with 30dB attenuation at the front end

    - also OCAGON OTLSO Twin LNB (26 MHz GPSDO) (same as DD4YR)

    - also 1.8m dish, however, not PF but offset.

    I get the following values:

    - lower CW beacon -73 dBm (this was adjusted manually by me, because it corresponds to S9 on a traditional S-meter)

    - transponder signal -108,7 dBm, so the beacon signal is 35,7 dB above the transponder noise

    - noise outside transponder -115,6 dBm, so transponder is 6,9 dB above the general noise leve.

    Simons SDR Console somehow calculates an SNR of the lower beacon to be 41,3 dB.

    DD4YR: Robert, good idea, but I was not able to measure the ground noise level, because I am glad that my 60kg 1.8m dish is pointed towards the satellite ;)

    EA4GQY: in my humble opinion 30 dB SNR is plausibel for a 80cm dish.

    Vy 73

    Holger 'Geri', DK8KW

    Hello all,

    I tried to find a way to transmit CW using a LimeSDR Mini and SDR Console. Until now I used an external tone generator (600 Hz), keyed externally with my electronic keyer (ETM-9COG).

    After searching the internet for a while I found tool called "Morse Keyer 4.3". This software makes use of a serial interface (RS232 or USB to TTL converter) as a keyer input and produces an adjustable tone that can be put on any of the installed (real or virtual) sound devices of your computer. I use the software with Windows 10.

    The tone frequency can be adjusted, as well as the softness rise/fall time, to avoid clicks (see screenshot).

    Resources and download:…rse%20Code%20Tools%204.3/

    I connected my electronic keyer output directly to the pins marked "Manual Key", see picture (source: MorsePower Website).

    For SDR Console, I use the SSB function with VOX enabled and the Virtual Audio Cable (B) as input.

    Have fun, see you on CW!

    Vy 73

    Holger 'Geri', DK8KW

    Well, Leonid,

    I hear what you are saying. The only thing I can add is that I have been using the 50 MHz IF without problems since last year very successfully, at home as well as portable. I have not measured any considerable drop in performance nor did I have any problem with my signal. it looks clean.

    However, I recommend to use a very steep filter as the ID-Elektronik filter mentioned earlier.

    I have, however, not yet tried any lower frequency, but I am confident that Ewald, DK2DB (= ID-Elektronik) can configure his interdigital filter so that the 28 MHz input of the DX-patrol does not leave any unwanted signals after the filter.

    Best 73

    Holger 'Geri', DK8KW


    Hello Mike,

    I use 50 MHz as IF for a BU500 up-converter and I ordered a filter from ID-Elektronik. It was adjusted particularely to attenuate the LO frequency of 2350 MHz and it does an incredible job to do that: the attenuation is 92 dB (!), while the pass-through attenuation is indeed very low. I am sure the filter could also be ordered for an IF of 28 MHz,

    Vy 73

    Holger 'Geri', DK8KW

    DB8TF: sorry, but my Excel-program was overwhelmed by the sheer number of data, also I was not aware that only 10.000 samples are collected in one go. Therefore I can not provide any graphics.

    My SDR-RTL-stick seems to stablizie after a few hours and stays pretty contatnd in the plus/minus 20 Hz window after that, so your OCXO seems to work fine.

    Best 73

    Holger 'Geri', DK8KW

    Hello all,

    I agree with what was already said: FT4 and FT8 are modes where a minimum power can be used for reliable communication. For instance, I was able to copy my own FT8 signal via QO-100 with an output power of 0.2mW at my 1.8m dish, resulting in an EIRP of 300mW (for comparison: the lower CW beacon is said to have 950 Watt EIRP).

    A FT8 or FT4 signal can only be successfully transmitted if your station has been optimized in regards to linearity of the entire system and frequency stability, insofar it is a part of keeping your station up to date regarding the "state-of-the-art", which is a basic requirement of an amateur radio station.

    Yes, there are stations who use much more power and communication is not really a challenge then through the satellite. However, believe it or not: it is fun! I have worked a few rare ones , such as EP4 and BY0 while I was assembling and soldering another project.

    Regarding satellite resources, by the way: besides CW and a few other digital modes, I can not see any more power and bandwidth optimized signal than the FT-signals. Bandwidth is below 50 Hz!

    Best 73

    Holger 'Geri', DK8KW

    P.S.: and yes, my main activity is rag chewing in CW with the occasional SSB QSO ... but playing around with some of the new stuff helps me to stay on top of technology :)


    Hello David,

    Not sure if JT65 is indeed the best mode -- it was just a coincidence that I tested it first and it worked, after I had problems with FT8. My transmitter is not too stable and has frequency changes of a few Hz while transmitting (as can be seen on the QRSS-plot) and JT65 seems to be quite immune against those. FT8 is not that tolerant. I will do further tests in the future.

    Would love to come back to 136 and 472 kHz but at the moment my antenna is not sorted out (top load radials caught by branches of trees) and my shack is a mess -- have to find the equipment first.

    Best 73

    Holger 'Geri', DK8KW

    Hello all,

    I realize that this thread is about a year old, but we have the sun passing behind QO-100 happening twice a year. Today I took the opportunity to record the noise of the sun passing behind my 1.8m CAS 180 Kathrein offset dish, pointing to QO-100.

    Reception equipment: Octagon LNB, stabilized with external GPS-disciplined TCXO, RSP1A, SDRUno to record the CSV file of the field strength. QRG: 10.487,500 MHz.

    I got a textbook-graph of the sun passing almost exactly behind my dish today.

    Vy 73

    Holger 'Geri', DK8KW


    Hello Etienne,

    Thanks for your detailled instructions and the hint about the SDR API-version that needs to be used. I already was wondering why my DVB-S2 Demod GUI software had stopped working.

    @ALL just a word of warning: when installing SDR API 3.03 as described, the latest version of SDRUo will stop working, because the software insists that it needs 3.06. At least on my machine this was the case, and I use the SDRUno software for numerous things, especially since I like the SNR and dBm measurements, which seems to be quite accurate.

    Best 73

    Holger 'Geri', DK8KW

    Hello all,

    Good old QRSS. I used to be one of the longwave 136 kHz pioneer back in the 90ies. At that time everybody told us that with our little antennas for the 2200m band we would not even reach the next village. It was the time befor JT65 and FT8 or WSPR. At that time we developed a very very slow type of CW (motto: "Longwave enthusiasts do it extremely slow").

    The principle is easy: you send CW signals with, for example, a dot length of 3 seconds and on the reception side you run a spectrogram software and let the naked eye do the decoding. The first LF transatlantic QSOs were made using QRSS.

    Today I remembered these good old times and thought that it might be worth to test QRSS on QO-100.

    This SPECTRAN screenshot shows a 3-second-dot QRSS signal, transmitted at 40dB below the beacon level. This corresponds to an EIRP of 95mW. The power at the feed of my 1.8m dish was 0.065mW!

    Explanation: the upper signals correspond to the dashes, the lower to the dots. You need a little bit of imagination to recognize my callsign: -.. -.- ---.. -.- .-- (DK8KW). Believe me, in the old LF-times we were used to read those faint signals from the screen right away, and we had fun QSOs over thousands of miles.

    It is fun now that QO-100 is there also for these (a little bit nostalgic) tests. And, by the way: QRSS beats JT65 by almost 5dB!

    Best 73

    Holger 'Geri', DK8KW

    Hi all,


    Great, Oliver, that was fun. I had 20 dB attenuation in my transmitter chain, so around 6 to 10 mW into the 1.8m dish, equivalent to something like 10 Watt EIRP! I couuld copy your signal ufb, and I even got called by a 4z1-station.

    Some people say that life is too short for QRP, but I love it!

    Schönen Sonntagabend und vy 73!

    Holger 'Geri', DK8KW


    Hello Oliver,

    Thanks for confirmation on the possibility to run very very low power on the satellite and sorry to hear that you sccidently destroyed your PA. Happened to me a lot when I was active on 136 kHz some 20 years ago!

    The next test is that I want to use a small antenna with no gain, such as a kind of "groundplane" and confirm if I can detect my signal with this antenna and about 300mW PA output. In theory it should work.

    Vy 73 and see you in CW-QRP!

    Holger 'Geri'. DK8KW

    Hello folks,

    I was curious what the estimated EIRP would be to be able to still receive a data signal through the satellite and I experimented a bit with the WSJT-X and JTDX-software.

    My setup: KX3 on 50 MHz (100mW) ==> 0 to 100 dB step attenuator ==> BU500 up-converter ==> filter ==> SG-Labs PA ==> 14m H-100 cable (approx. -7dB) ==> 5 turns helix ==> 1.8m offset dish (CAS 180).

    According to my measurements the entire setup is pretty linear, so that I can adjust the power accurately by using the 0 to 100 dB step attenuator between the KX3 and the BU500.

    I adjusted the power in a way that my reference power gives a signal that is at the same level as the lower CW beacon. According to some information that was distributed earlier, this corresponds to an EIRP of about 950 Watt (= 300mW into 3m dish in Bochum).

    I used a couple of modes but finally settled on JT65 to do my tests.

    Result: I can safely decode signals that are 35 dB below the maximum EIRP of the beacon signal, meaning, that an EIRP of only 300mW is sufficient to decode data signals. The table below shows some of the results. The fourth line was received with only 30 dB attenuation, equivalent to 950mW, the others with 35 dB attenuation = 300mW EIRP.

    Best 73

    Holger 'Geri', DK8KW

    1101 -20 1.0 888 # TEST DE DK8KW

    1103 -21 1.0 888 # TEST DE DK8KW

    1119 -22 1.1 890 # TEST DE DK8KW

    1123 -15 1.1 877 # TEST DE DK8KW

    1125 -21 1.1 878 # TEST DE DK8KW

    1127 -21 1.0 884 # TEST DE DK8KW

    PY4ZBZ: Hello Roland,

    According to an information that was distributed a while ago (and when I remember that right) the E.I.R.P. of the CW beacon is 950 Watt. Plausible, because the dish in Bochum is a 3m parabolic prime focus antenna and the power is around 300mW.

    Best 73

    Holger 'Geri', DK8KW

    Hi again,

    I just confirmed it with the Cornwall websdr. The lower beacon has about -77dB peak (measuring the "Mark" frequency @ 300 Hz filter width), the upper beacon -80dB.

    Not that it really matters, we still can use either beacon as a reference of course ... ;)

    Vy 73 and have a nice evening

    Holger 'Geri', DK8KW

    Hello Matthias,

    >So presently both (CW) beacons can be used as level reference.

    That is interesting what you say. I use the RSP1A at an intermediate frequency of around 1100 MHz and, independent of the selected bandwidth, the upper CW beacon is definetely 3 dB weaker here than the lower beacon. This also applies to my own signal, transmitting near the lower and near the upper edge of the transponder.

    I will check with a different set up and try to find out the reason for this.

    Best 73

    Holger 'Geri', DK8KW



    For me the lower beacon was always the reference. The difference between the "Mark" frequency of the lower and the upper CW beacon is about 3 dB, which probably is due to the reduced sensitivity of the band at 10.490,000 MHz.

    So, until we get any other instructions, I try to keep my signal below the level of the lower CW beacon.

    But, as DB2OS mentioned in one of his posts, calibration of LEILA is not yet completed and I guess there also might still be some adjustments going on, which means we just have to wait and see how things work out.

    Best 73

    Holger 'Geri', DK8KW