Posts by DK8KW

Achim,

thanks, that is a helpful idea. I do have a LimeSDR around somewhere and will feed a signal from a directional coupler between the Pluto and the bandpass filter into the lime to monitor the output of the Pluto.

Vy 73

Holger ‚Geri‘, DK8KW

Hello YLs and OMs,

I am using a typical Pluto setup (Pluto —> Bandpass Filter —> Pre-Amplifier —> SG-Lab PA V3) —> Antenna), controlled by the latest developer version of SDR Console (3.0.26).

Since some time now I do have a kind of QSB-like effect on my QO-100 signal. While the reception remains constant, my own signal gradually goes down by up to about 10dB. After a while it goes up again, sometimes it takes a little longer to do that. I have checked all components of the setup (amplifiers, cables, antenna) and it seems to be the Pluto itself.

Anybody else ever experienced this behaviour? Any suggestions?

Thanks, best 73 and stay safe!

Holger ‚Geri‘, DK8KW

SV1BDS

Hello George,

I had a successful reception of DL0SHF on June 2nd, 2020. The moon passed about 1.5 degrees below the beam of my 1.8m offset dish, so I adjusted the inclination of the antenna before the moon pass.

I used a GPS-controlled LNB and the RSP1A for reception. The DL0SHF signal was audible for a few minutes and I was able to decode the CW signal by ear. Due to the Doppler effect the RX-frequency was about 6 kHz above the transmitting frequency of the beacon.

All in all a very exciting and rewarding experience!. Good luck with your redeption.

Vy 73

Holger ‚Geri‘, DK8KW

Hi folks,

An addition to the software for this device: there is a pogram that can be downloaded for the vendors websites. This, however, allows just changing the basic attenuation value and this is simpler if you do it with the five buttons.

Currently on Ebay there is a guy who wants to sell a software written in Python to control the attenuator (just look for ATT-6000 and Python). I am no expert in Python and, to be honest, that software seems to be a bit overprozed.

Third option: I found a software called PureBasic (see https://www.purebasic.com/). It reminds me of my old C64, HP-Basic and QBASIC times and it is simple enough for me to handle it, and strong enough to write a small control program for the attenuator.

A demo version limited to small programs (about 800 lines) is free of charge.

Vy 73

Holger 'Geri', DK8KW

Hello YLs and OMs,

One thing I learned very early, when I started with QO-100 last year: it’s all about the proper power level!

This resulted in the fact that I today own way more attenuators than amplifiers. You see so many distorted signals on QO-100 where you can see that the amplifiers are driven beyond their linear range. A little attenuator at the right place would be sufficient to adjust the signal.

My latest acquisition is a 60dB 6GHz programmable attenuator called ATT-6000. It is offered by several people on Ebay, for example. On the internet there are a few discussions about this type of equipment, for example on an Amateur Radio Astronomy website: http://cygnusa.blogspot.com/20…at-for-att-6000-step.html. Here, the 31dB-version is discussed.

The ATT-6000 comes with in a machine finished metal housing that looks very well made. The little unit is powered via an USB-cable. This also allows the programming of the device.

Attenuation adjustment range: 0-60dB

Attenuation step: 0.25dB

Max. frequency: 6GHz.

More date can be found on the internet, e.g. on Ebay. Also, some measurement-charts are available, e.g. about the frequency range and the accuracy.

I have put this device directly behind my Pluto. On 2.4GHz, the base attenuation is in the 5dB range. For my applications this is not relevant. What I want to do is to test various modes on QO-100 in order to find out to what level below the beacon level communication is still possible.

Once I adjust my TX output signal to the beacon level I can reduce my output power accordingly. The absolute attenuation seems to be a little bit lower than said. I measured about 4.6 to 4.8 dB per 5dB attenuation step, however, that might be a problem of the accuracy of my measurement setup. The repeatability of each step, however, lays within a few tenth of a dB. The attenuation can be adjusted with the 5 buttons on the housing of the unit.

The ATT-6000 can also be remote controlled. I used a simple terminal program. Once connected, the device is recognized as a Profilic USB to COM adapter. Basic communication characteristics are: 115200 Baud, 8 Bit, 1 Stop-Bit, NoParity.

The attenuation value is sent to the device by the ASCII-string wv0xxxx, whereas xxxx is the value of the attenuation. 1225, for example, represents an attenuation of 12.25dB 8see pictures). I need to find a simple programming language (I am not yet too familiar with all the modern stuff such as Python), the I can make the adjustment of the attenuation even easier.

This attenuation device is definetely somehing I can recommend for the QO-100 operator. It can be used, for example, to find the proper attenuation value between power amplifiers so that the signal quality is improved. Once measured, which value is needed it can then be replaced by a fixed attenuator.

Vy 73

Holger 'Geri', DK8KW

P.S.: Again, I am in no way connected to anyone who offers this device.

Hello folks,

Last year, long before I had a Pluto, I purchased an unknown amplifier from Poland on Ebay, that was just marked "Mikom MLA 901-1459". Pictures of the front cover show a frequency range of 2439-2576 MHz.

In the meantime, I have made some measurements and made this amplifier a regular member of my amplification chain. Especially in combination with the new version of the SG-Lab V3 20Watt amplifier the MLA 901-1459 offers a useful tool to use the full power range of the Pluto to drive the SG-Lab PA to its full potential.

If you enter the "MLA 901-1459" in eBay ou can see that these surplus amplifiers are still available. It is a very well designed and built commercial little amplifier. Perhaps this is a good alternative to the little Chinese amplifiers that usually come without a housing.

Below are two amplification measurements, one with just the pre-amplifier (MLA 901-1495) and one with the entire system (Pre-Amplifier plus SG-Lab V3. Measurements were made with the SATSAGEN-Software and the Adalm-Pluto. Amplification of the MLA-preamplifier is around 25dB.

Vy 73

Holger 'Geri', DK8KW

P.S.: I am in no way connected to the seller of this surplus equipment, I just want to give some useful hint to people looking for such equipment.

@SWL - markro92

Hello Marcel,

I did reception tests with the 2.0.20-version today and they all were very successful. Once I found the right adjustments, I was able to jump to another stations frequency, change the bitracte and wait a few seconds and the signal was there. Sometimes, changing the bitrate up or down by one bit helps to find synchronization quicker. Great job, thanks!

I have two request respectively questions:

1st: would it be possible to allow the L.O. frequency to be entered with a few digits behind the comma? I use a LNB with a 26 MHz GPS-controlled oscillator and my L.O. frequency actuall is 9388.888 MHz. But I can only enter freq_lo0 = 9389.

This would help to quicker enter the right frequency.

2nd: when I try to change the IF frequency with the scroll whee of my mouse it changes the frequency in MHz steps. Is that anything that has to do with my computer or is it something in your software? I would be able to change the frequency in smaller steps, actiually, for example like 100kHz.

Thanks and vy 73

Holger 'Geri', DK8KW

OE5PLN,

hello Peter. can you use the VOX to trigger the relais-PTT in SDR-Console? if not: it might be worth to ask Simon if this could be implemented.

Vy 73

Holger ‚Geri‘, DK8KW

Hello Thorsten,

I am not familiar with the DX-Patrol up-converter but I assume that it is working as a linear converter. So what you would need is a relatively cheap step attenuator on thw input side of the converter to reduce the output power. This step attenuator only needs to be suitable for the input frequency and not for 2.4Ghz. I have seen those already for around 20 or 30 Euro.

The SG-Lab PA is very linear, even down to very low power, see my report at

SG-Labs 20 W PA V.3

Vy 73

Holger ‚Geri‘, DK8KW

Hi Oliver,

I have a different GPDXO, made in Germany by a company named Cartain. It was a bit cheaper than the Bodnar, and it was abvailable at the time I bought it and Bodnar had a longer delivery times.

What I did was to check what peope said about the Bodnar-Voltage at 8mA and I basically use the same voltage with the Cartain. I only need a single GPS controlled frequency of 26MHz. I split the output through a Mini Circuits splitter (so at least losing 3dB) and then put another 3dB attenuator in the line before I feed the signal directly into the Pluto.

The other line goes via a 20m coax cable to the LNB and stabilizes the reception. I am very happy with this entire setup.

Vy 73

Holger 'Geri', DK8KW

HB9SKA: what my equipment is concerned, I don't believe in covers ... my LNB as well as the helical antenna are in the open environment, so the front end of the LNB surely was wet during the rain. However, when a "normal" rain occurs and the surface of LNB lens is wet I can measure no attenuation.

Vy 73

Holger 'Geri', DK8KW

Hello all,

Yesterday I had the opportunity to record the level of the CW beacon while a heavy rain shower came down.

The nominal value I adjust the beacon to is -73dBm. You can see from the picture that the lowest level during the rain is around -88dBm (only look at the upper values of the curve -- I tried to produce an envelope in Excel but that seems to be a challenge in itself).

So the maximum attenuation is 15dB. My uplink signal, adjusted to the beacon level, also had the same attenuation as the beacon, which means, that the 2.4GHz signal seems to be much lesse affected by the humidity in the air.

Did anyone else took similar measurments?

Best 73

Holger 'Geri', DK8KW

P.S.: I don't really know if this is relevant and if the attenuation is the same for different antenna sizes. My QO-100 antenna is a 1.8 Meter offset dish from Kathrein (CAS 180).

Hi Oliver,

You were very brave to desolder the Pluto TCXO -- had somone else doing that for me. I also work with an external GPSDXO, also connected via a 3dB attenuator.

Vy 73

Holger 'Geri', DK8KW

Hi Matthias,

Thanks for the hint to Sigis recommendation. It worked!

DO1OHB: Oliver, Sigi wrote in the beta tester forum for SDR-Console:

"that is just easy cause you have TWO DRIVE sliders

one in the tx options and one in the main tx dsp panel

turn main at 100%

then set the slider in tx options (search under "audio/gain") to your max allowed level (say 80% or so or if you have a high gain setup maybe only 50 or 60?!?)

then you can not overdrie it anymore ... just do not set that slider higher as 80 ... in main tx box (dsp panel) you can then only turn it further down ... as an example ... i have set my drie in tx options to 85% and in dsp panel to 90 ... i can go a bit hgher if needed (crank up to 100 in dsp panel) but then i begin to have a bit of intermod (other call that splatter) ... so i set my level to be maximum where it is still clean in normal use ... and have some db left for voice peaks (or to break a pile up hi hi) ... and do not have the danger of overdriving the amp".

Might be useful for your setup, too.

That saves me at least an attenuator.

Vy 73

Holger 'Geri', DK8KW

Thanks, Matthias,

In the meantime i switched to an Adalm-Pluto and this is exactly the feature that I am missing in the Pluto setup (or that I am too stupid to find .. ).

Vy 73

Holger 'Geri', DK8KW

Hello Oliver,

>And I know myself setting a Driver to 50% will be forgotten and 100% will be the standard

Yes, I know what you mean. Thinks that can go wrong will go wrong Murphys Law). I have just send a feature request to Simon to limit the gain slider of SDR Console to a certain fixed vakue somewhere in the menues, so that a this value can only be exceeded if really needed and not in day-to-day operation. Hopefully he will come up with a solution.

Vy 73

Holger 'Geri', DK8KW

Hi,

I can second, what Oliver writes. I also received the V3-PA yesterday and did some tests and measurements and I am very happy with this new version. I already use the V2-Version in my portable setup, perfectly fitting to the output of the BU500 up-converter.

The RF-Vox is irritating at first, because when you connect the PA to 28 Volt there is almost no current. The build-in ampere meter of my lab power supply only shows 2 digits after the decimal. I only saw "0.00" and thought, that the PA was not working. However, as soon as the input power is raised above a certain threshold (in my setup around -3dBm), the RF-VOX kicks in and the current rises above 0.6A @ 28V.

You can also activate the PTT permanently and this leads to a bias current of 0.58A. With the PTT activated I was able to amplify signals of down to around -30dBm, resulting in an output power of around 0dBm, so the amplifier is also well suited for QRPP-experiments.

All my measurments confirm the claims of SG-lab. I mounted the amplifier onto a heat sink with dimensions of 15x20x2cm and even at transmissions at 20 Watt output, the housing of the PA only got slightly warm.

The plan is to install the amplifier outside in a waterproof enclosure close to the 1.8m offset dish and possibly also start some experiements with DATV on the wideband transponder later this year.

DO1OHB: Oliver, I would not be too concerned about putting an attenuator between the pre-amplifier and the PA. The pluto gain itself can be adjusted pretty linearly, and if you set your Pluto drive somewhere between 30 and 50, you already should be in the usuable range for the input of the SG-Lab Pa. The maximum input of the PA is 20dBm, and even if you accidently set the Pluto-gain to 100% you will most likely not exceed this level, because SMA plugs and cable between the pre-amplifier and the PA will have more than 1dB attenuation.

Vy 73

Holger 'Geri', DK8KW

Hi,

While I agree that the full duplex operation is very useful, my interpretation of the rule

"Full-Duplex operation is mandatory (you must be able to monitor your own downlink while transmitting!)"

is that I am able to MONITOR my signal, not necessarily permamently to listen to it.

It would make me completely crazy if I had to listen to my own CW transmission with the delay of the satellite link and the SDR processing. So my way to comply with the rules is that I have SDR Console running and closely look at my own signal while I transmit. This allows me to see if anyone wants to interrupt me, or if my signal gets distorted in any way or my signal strength accidently rises above the beacon level.

Vy 73

Holger 'Geri', DK8KW

Hi folks,

I recently modified a few Airlink 60 antennas (see figure 1). This industrial 2.4GHz antenna is made by SSB Electronic. The original antenna has a vertically polarized patch in it, made by GlobeSat in Denmark. This patch is glued in the focal point to the inside of the radom (see figure 2).

I replaced this patch with a WA5VJB-patch, LHCP (Hi Z to compensate for the effect of the radom, as recommended by WA5VJB), so that the antenna is transmitting right hand circular polarization (RHCP) (see figure 3).

As I have a few of these antennas available, I could directly compare the circular antenna with the vertical linear one. The difference I measured in my QO-100 signal strength was between 2.1 to 2.5dB.

Best 73

Holger 'Geri', DK8KW

Figure 1: Airlink 60, an industrial prime focus dish made by SSB Electronic.

Figure 2: The inside of the antenna can be accessed from the back. Here, the original linear (vertical) polarized patch can be seen.

Figure 2: The original patch was replace with a WA5VJB patch.

SV8QG

Hello Alex

>I’m wandering if I can paint the hole POTY with plastic paint

I have no experience with the Poty, however, when I tried to glue parts of a helical antenna to the isolator I used a two component plastic glue. That immediately changed the entire resonance of the antenna and I quicky had to remove the glue again.

So I recommend to check the electrical parameters of the plastic paint first. You might use a sheet of plastic material and check, if it gets warm in the microwave oven. If not, paint it with the plastic paint you want to use. If that doesnt warm up it might be OK.

Best 73

Holger 'Geri', DK8KW