Posts by HB9VEQ

Dear All,

I'm building a DATV amp based on a BLC9G22XS-400AVT board. I will put this board into an aluminum box from Hammond and that box on a big heatsink.

Now I wondering what would be the best option to avoid emission through the DC supply line. I was thinking of using feed through caps, but I'm having doubts that this works as permanent solution. Because if I solder the DC wire directly to the ft cap on the outer side, I the mechanical stability (-> bending of the DC supply line) is probably not very durable. So I would prefer something like a socket (e.g. banana connector).

Do I miss anything or am I thinking too complicated in this case? Ferrite..?

Please can someone help me out and share his experience with shielded amplifier enclosure and the DC supply line?

Thanks in advance

Mic

Hi!

I'm having issues receiving DATV signals from WB transponder.

My current set-up is:

85cm dish

Opticum LSP-02G LNB (-> supply voltage is 18.5V)
Adalm Pluto and/or RTL SDR USB Stick

I tired with SDR Angel and with this software. But the video and audio is mostly not stable...

I played with the BB gain setting and the current setting gives me the best result.

Is there anything else I could optimize in the settings to get a better signal?

On NB transponder my SNR is 31 dB (CW beacon) - is that enough for receiving DATV signals via WB?

Thanks + 73

Mic

Very helpful people here! Again, thank you very much for the detailed explanations.

I have less experience in electronics, so I trusted the information from manufacturer (too much) and didn't question it.

It 'sme again.

I did the math but I'm still confused.

Because as I said in one of my last post I can not understand why there are two values (dBm / CMOS voltage).

If I take the dBm value and calculate the corresponding voltage I could not get close to the 3.3V CMOS.

square wave +13.3dBm @ 50 Ohms =

21.38 mW, 1.034 Vrms (2.068V p-p), 20.68mA

Help - where's the error in my logic?

Thanks in advance!

Makes perfect sense.

Thank you for the excellent explanations.

I'm still struggling with this…

I'm a bit confused about the output voltage of the GPSDO because the homepage states the following:

Both output signals square wave at 3.3V CMOS levels with 50 Ohms characteristic impedance.

Output power level (measured at 10MHz, fundamental power channel):

+13.3dBm, drive setting 32mA

+12.7dBm, drive setting 24mA

+11.4dBm, drive setting 16mA

+7.7dBm, drive setting 8mA

From my point of view these values are contradictory because CMOS voltage != dBm related voltage:

7.7dBm at 50 Ohms = 1.535V p-p

13.3dBm at 50 Ohms = 2.924V p-p

I can also measure with a oscilloscope an output voltage of ~3.3V p-p (no matter which drive setting).

Where is my mistake?

Uh - 1.3 V p-p

I wasn't aware about the input limits of Pluto's SDR chip. Thank you for highlighting this!

According to the GPSDO specifications the output signal is a square wave at 3.3 V CMOS level. Due to the lack of a proper oscilloscope I can only measure up to 20 MHz. Up to 15 MHz I can measure an output level of 3.3 V p-p (without load).

So 3.3 V p-p is obviously way too much.

Maybe a simple voltage divider is a good solution to protect the Pluto from getting fried?

DJ0MY: I really appreciate your feedback. I'm wondering why my Pluto is still alive because of the high clock input. I have also set the GPSDO drive to the lowest level (8 mA).

Hopefully someone has still the measured results and can post them here.

Hi all,

I'm using a Adalm Pluto with an external GPSDO from Leo Bodnar (40 MHz / 8mA drive) . Everything works quite good.

Today I had a QSO with an OM via QO-100 who told me that I should not connect the GPSDO directlyto the Pluto because the SDR chip might get fried. After the QSO I was a bit scarred and therefore I searched in this forum for more information. But I could not find any recommendation to add an attenuator between the GSPDO and the Pluto.

Sorry - maybe a strupid question:

Is it really true that my setup might damage my Pluto?

Thanks!

73 Mic

Hallo,

der Einbau des Inverters in den Pluto hat geklappt. Der Aufwand war wirklich überschaubar, nur die Inverter sind ausgesprochen miniatur.

Auf dem Web-SDR ist mein Signal jetzt richtig "sauber".

DB8DT: Danke für alles!

73 Mic

Hallo DB8DT,

das Konzept gefällt mir gut, da der Aufwand überschaubar ist!

Ist das ein SMD Inverter?

Falls du noch einen Inverter überzählig hättest, würde ich dir gerne einen abnehmen

73 Mic

Quote from dd9fj

Pluto with to low LO..

Hi Michael,

as mentioned in my previous post, we are also discussing this topic in another thread in the German part of the forum.

We are wondering if other users are also facing similar issues with the Pluto.

You suggested that the issue might be related to a low LO level. So now I'm curious if this is a guess or do you already have some kind of practical experience with the issues?

Thanks for any kind of feedback.

73 Mic

Hallo Ulrich,

Danke für die Bilder. Es sieht tatsächlich ähnlich aus, allerdings sind die Spurs etwas stärker und der Abstand zum Center ist grösser. Die Spurs sind hier nicht statisch, d.h. sie verändern sich in Abhängigkeit zur TX Frequenz (nicht linear).

Ich bin schon sehr neugierig auf die Testergebnisse mit MAR0685.

73 Mic

Guten Tag Ulrich,

jetzt bin ich wirklich froh, dass ich nun einen "Leidensgenossen" gefunden habe Zunächst vermutete ich, dass ich den Pluto durch die Modifikationen beschädigt hatte. Theoretisch müssten ja auch viele andere Benutzer des Plutos (in Kombination mit getauschtem TCXO) ähnliche Probleme haben...

Tolles Projekt und (in meinen Augen) eine wirklich kreative Lösung! Herzliches Danke für das Teilen!

Konntest Du damit den Nebenträger eliminieren?

Bei meinem Pluto sind neben dem von Dir genannten Nebenträger auch noch weitere Nebenaussendungen vorhanden. So z.B. bei etwa +180kHz und 370kHz.

Ist das bei Dir eben auch der Fall?

Laut Datenblatt des AD9363 ist auch ein LO mit CMOS Clock möglich, so werde ich zunächst einen solchen TCXO testen.

73 Mic

Quote from dd9fj

Pluto with to low LO..

That's very interesting.

With one of my Plutos I also noticed some issues which seem to be related to a low LO. I have reported this also in another thread of the forum some days ago:

-> https://forum.amsat-dl.org/index.php?thread/3158-umbau-adalm-pluto-tcxo/&postID=14145#post14145

Is this a know issue with the Pluto?

Hi all,

with my second Adalm Pluto (for mobile operations) I noticed some unwanted spurious in the hf output - they are quite low, but still notable. This Pluto got a new TCXO (the well known Abracon ASTX-13-C-40) and after that the spurs were visible in spectrum. The other Pluto in my shack is synchronized with a GPSDO from Leo Bodnar, no problem with stability or spurs.

I did some readings and tests and finally I came to the conclusion that there might be a problem with the peak-peak voltage of the clock. According to the AD9363's specifications for optimal performance, the clock (XTALN) should be 1.3 V p-p. But according to Abracon's specifications, the TXCO only generates a clipped sine wave output of 0.8 V p-p.

After this finding I did some more tests with my other Pluto and lowered the GPSDO's clock output voltage with the help of an attenuator to 0.8 V p-p and then there were also spurs in the output spectrum visible. So it seems like the AD9363 is very sensitive to the reference clock and if the peak-peak voltage is below 1.3 V it will generate unwanted spurs.

Now I think that the Abracon TXCO is not a perfect replacement for the original oscillator of the Pluto - if you are looking for stable AND clean TX signal.

I thought to adjust the coupling capacitor between the TCXO and XTALN or add a volatge divider (C123/C124) but since the oscillators output voltage is below the recommended value it would not be helpful.

Has anyone else made similar observations and are there any other LO recommendations or other ideas I have overlooked so far?

Thanks for any input!

73 Mic

Dear Peter,

I really appreciate your kind answer

73 BR Mic

HI all,

I have (maybe) a strupid question regarding the DJ7GP-Feed:

I checked the DC resistance of the 2.4GHz Patch and the meter shows 1.1 Ohms. So now I wonder if the antenna works like a folded dipole which forms a closed loop?

Thanks!

73 Mic