Posts by DH2VA

dbFS is decibel relative to the full scale of the SDR receiver (which is max sum amplitudes of all signals to the SDR input). It is rather pointless to give any numbers here as these will vary depending on LNB, cable used, temperature to only name a few.

The ONLY way to properly max the antenna pointing is to max on any of the beacon signal levels, regardless of the reading itself. Then to compare different setups to each other you have to check the transponder excess noise referenced to the thermal noise outside of the transponder BW. Select a display BW of at least 3 MHz and you should see a hump about 600 kHz wide and 3-4 dB sticking out of the noise floor left and right. This is the transponder passband and the 'stick out' value is the only one which is independent of the SDR software used. For 80cm, 3-4dB is fine, if you don't see this I would not touch the TX and figure out RX first.

RF is easy, especially microwaves but good mechanics design is hard. Fellow hams usually laugh at me.. only once. But we all learn from it so this is good.

The LNB went up, so the beam went down. You have to adjust the dish as a whole a bit up again..

you have to realign the dish after this modification

Robert hat recht, VSWR sagt nichts ueber Zirkularitaet aus. Und noch weniger ueber das Strahlungsdiagramm, ein gutes VSWR kann ein lausiges Diagramm haben und damit ein schlechtes Feed darstellen.

I don't think the OMs with an errornous setting of 3.0 kHz in the TX modulation filter (SDR console for example) are the problem of this topic but rather the few gentlemen overdriving their PA and therefore generating up to 10 kHz wide splatter (which is actually IM3). Many operators have good to excellent signals, some of the overdrivers are reasonable once you explain the cause of their bad signal to them (actually, the readability of the voice does suffer considerably as well). The very small fraction of those who don't care, I have no idea what to do.

Der Vollstaendigkeit halber: AMSAT-DL nutzt bei seinen Bodenstationen in DL und Katar ebenfalls TS-2000 dank der grosszuegigen Unterstuetzung von Kenwood und JAMSAT. Da diese Geraete bei uns aber fest verkabelt sind haben wir den zum Empfangszweig gehoerenden Sender 'totgelegt' indem wir die entsprechende Steuerleitung im Geraet abgezogen haben.

Thanks to DL5QY sending me his dead PLUTO, I was able to trace down the problem and offer an explanation for the probable cause.

TLDR: GND potential difference between SMA and USB frying L7 which then shorts the internal 5V line.
A more detailed diagnosis is attached in the zipped PDF.

Please be all reminded that the transponder will have a big influence itself. Cannot give numbers due to NDA but rest assured, what we all currently see is really good by all means.

It depends. If they actually require high speed S-band downlink then 4m might be necessary due to their link budget.
HOWEVER: the required pointing and tracking accuracy coupled with the high angular rates for a LEO satellite will make this super complicated and carries a huge risks for problems and/or failures.

Bottom line:

if you don't need 4m, than I completely agree with HB9SKA

if you do need 4m because of link budget, you have designed your mission wrong.

Point taken! I have forwarded the question to the gentlemen at BATC with the request to include a contact adress on the webpage in the future.

Allan deviation is stability.. 130Hz in 10 GHz is accuracy. Check here for a good explanation of the subject.

That said, there are numerous explanations for this offset including hw failures. Maybe telling the WebSDR team directly?

Return loss (or matching) is only one side of the coin. 3 turn helix feeds are known to have not very good circularity. The only way to measure this is on a test range with two antennas (TX-RX, one preferable being a linear antenna) used and one being rotated along its boresight axis. Good circularity would result in no change of received signal level while rotating.

what about asking our friends from ISISspace? I think they had plenty of customers on board..

you also have to close and repoen the sdr-console application

The reason why I was asking about the USB to ethernet adapter is that after all, there is a Linux OS running on the Pluto and some ethernet chipsets might not be as well supported as others. For reference, I followed the tutorial from DD1US and everything worked straight as described when using the exact same ethernet device.

http://www.dd1us.de/Downloads/…20Area%20Network%20v2.pdf

maybe I missed it but have you tried any other USB-Ethernet Adapter? Does the Pluto work when directly connected to a Laptop with USB? I think some ethernet adapters give more problems than others, can you post a picture or model of your adapter?

sounds good to me. REFIN has a 50 Ohm input termination and TRX an attenuator which should look like 50 Ohms as well. So both are 50 ohms to ground and consequently 100 ohms to each other.

For the RF path I would settle for nothing less then ATC capacitors. You may use a trimmer for finding the initial setpoint but I would then measure the capacitance and replace it with a suitable ATC type cap (maybe even two in parallel to reduce ESR). Lowest ESR @ GHz and therefore small losses, little self-heating. Both desired for RF output path.

Mea culpa, ich hab den Schaltplan falsch herum interpretiert. Jetzt aber:

EINGANG -> Abschwaecher -> MMIC -> 2x LPF -> combiner -> 2 parallele PAs -> combiner -> AUSGANG

Sorry fuer die Verwirrung, geht auf mich. Dann ist ein Tiefpass am Ausgang nicht schlecht, aber evtl. nicht absolut notwendig.

Grund: das allseits verwendete Patchfeed (und auch alle Helix Antennen) sind eher schmalbandig und werden auf 4.8 GHz nicht mehr so gut funktionieren. Also wird eine evtl. erzeugte Oberwelle kaum abgestrahlt. Weiterhin ist es fuer alle PAs von Vorteil, wenn sie deutlich unter dem P1dB Punkt betrieben werden (weniger IM3, d.h. sauberes Signal) und dann gibt es auch weniger Oberwellen.

Wenn jemand die Oberwellenunterdrueckung der 6W PA fuer verschiedene Eingangsleistungen mal messen koennte waere das natuerlich Spitze, hi. Dann wuessten wir es genau.