Posts by DD1US
-
-
Hello Bert,
have a look at this presentation, especially pages 25-28.
Kind regards
Matthias
-
Hallo Thomas,
nein ein Schaltregler ist ein DC-DC-Wandler.
Hallo Roland,
Deine Rechnung oben hinsichtlich der Berechnung des Intermodulationsabstandes ist grundsätzlich ok.
Wie man aus den Messungen im AMSAT-DL Journal sieht ist der Übergang des mehrstufigen Verstärkers
vom linearen Bereich zum Sättigungsbereich sehr "weich". Damit dürfte die Formel oben nicht mehr
anwendbar sein. Es ist also wohl eine echte 2-Tonmessung nötig um den Intermodulationsabstand zu
ermitteln.
Gruss
Matthias
-
Hallo Roland,
ich habe bisher keine 2-Tonmessungen durchgeführt aber werde das mal bei Gelegenheit tun, wenn ich Zeit finde.
Ich kann aber sagen, dass das Signal des Upconverters in meinem Portabelsetup sehr sauber ist.
Ich steuere die PA mit ca. 2-3W aus und habe keinerlei Nebenaussendungen oder Intermodulationen gesehen oder von anderen OMs berichtet bekommen.
Viele Grüße
Matthias
-
-
Hi Kurt,
looks very nice. Congratulations.
What is the insertion loss you are measuring at 2.4 GHz ?
Kind regards
Matthias
-
Hello Geri,
reading the thread again I guess you were referring to the Pluto and not the Lime.
As far as I know the feature I described above is only available for the Lime.
Sigi has described in the SDR-Betatester-Group a way how to do it with the Plut. More complicated but also possible.
Kind regards
Matthias
-
Hello Geri,
if I understand your problem correct there is already a solution in SDR-Console:
go to the "LIME-SDR setting" and then to "Drive"
Here you can activate a "custom drive range" with a checkmark.
You can then set the minimum and maximum drive levels.
Here is the explanation from the help window in SDR-Console:
Drive
The default drive range of the LimeSDR is 73dB which is far more than required, also this makes it difficult to select the desired value. A custom range makes adjustments much easier. The exact values you select will depend on the amplifiers used between the LimeSDR and your antenna.
Maximum
When running the LimeSDR at maximum output the signal may suffer from Intermodulation distortion (IMD), so set the maximum value to -10dB or -15dB.
Minimum
Set the minimum value somewhere between 20dB and 30dB lower than the maximum.
I have set here my Lime-USB to min -40dB and max -10dB. For me a range of 30dB for setting the TX output power is fully sufficient and with the max of -10dB I cannot overdrive my PA and the output signal from the Lime is nice and clean.
Kind regards
Matthias
-
Hallo Joachim,
ja, man sollte auch TCXOs stets vor Luftzug schützen. Ich habe meine Transverterkomponenten auch stets separat in einem Weissblechgehäuse eingebaut. Etwas Schaumstoff auf / um den TCXO positioniert reicht aber auch schon aus, um ihn thermisch zu isolieren.
Es gibt auch ein schönes 3D gedrucktes Gehäuse in welches man das OLED einbauen kann und ausserhalb des Transvertergehäuses betreiben kann. Im Amsat-DL Journal ist auch davon ein Bild zu sehen und die Info wer diese Gehäuse drucken kann.
Viele Grüße
Matthias
-
Hallo DL6SIX,
eine genaue Beschreibung des OLED Displays und wie man es anschliesst ist im aktuellen Journal der AMSAT-DL zu finden.
Es ist dort beschrieben, wie man es mit einem Flachbandkabel anschliesst um es in eine Frontplatte zu montieren und auch,
wie man es auf die Platine montiert.
Viele Grüße
Matthias
-
Hello Chris,
uuh, powerline is one of the devils for Ham Radio.
Did you check the spurious emissions on HF and VHF ?
Kind regards
Matthias
-
Hello Robert,
I habe modified my Pluto inject an external 40 MHz reference signal from a GPSDO. This is probably the ultimate solution but you then need a GPSDO. I am using the single unit from Leo Bodnar and I am very satisfied with it.
Hello Achim,
yes of course with lower frequencies the drift gets smaller ...
Kind regards
Matthias
-
Hello,
you cannot really use the Pluto for narrowband transmission on 13cm band.
I measured the drift of my unmodified Pluto early last year and the drift is about 10Hz per second even after one minute.
Right after switching to TX it is even higher (25Hz/sec). Of course this might be slightly different from unit to unit but I am
sure it is always too high.You can find my measurements here:
Adalm Pluto Drift Measurements
Kind regards
Matthias
-
Hallo Ulrich,
sehr interessant. Was meinst Du mit Gewinn ? Antennengewinn, Verbesserung des SNRs, ... ?
Viele Grüße
Matthias
-
Hi Gustav,
welcome to AMSAT-DL.
I will try to make sure that you will get the latest magazine.
Kind regards
Matthias
www.dd1us,de
-
Hi Gustav,
a detailed description how to connect the 1.3" OLED to the AMSAT-DL Downconverter V3d is in the new AMSAT-DL Journal which our members should receive in the next 5 days. Both options: how to mount the OLED directly on the board and how to connect it when
assembled in an encasing is explained.Are you already a member of AMSAT-DL ?
Kind regards
Matthias
-
Hi,
I suspect that the problem occurs when the supply voltage gets switched on with a high slew rate.
Maybe the original power supply has a well defined slope of the supply voltage ramping up.I had several problems when I started to switch on the supply voltage using a relay in the drain supply.
Before I had tested and several of those amplifiers with a lab power supply and never had a problem.
I am just guessing but maybe my observations can help to trace down the root cause.
Kind regards
Matthias
-
Alex,
this is not related to the satellite.
If your uplink antenna (feed) is really linear polarized then you should not see a difference in the downlink signal strength when turning your feed.
However make sure that you are not turing the uplink feed and downlink feed at the same time as this will influence the downlink strength.
It might be better for such a test to use the Web-SDR to watch the downlink signal when optimizing the uplink antenna (feed).
The QO-100 transponder has not changed.
Kind regards
Matthias
-
-
Hi Heiner,
besides the lens, is this a PLL LB with no wobble and thus suitable for NB operation ?
Kind regards
Matthias
