Posts by DH2VA

caps for gate voltage, drain voltage or RF path?

Filter am Ausgang weil der Final Amplifier ebenfalls Oberwellen produziert.

Rechnen geht wohl nur mit einer Simulationssoftware, aber mal ein paar grundlegende Uberlegungen und Analogien zu einer Kamera.

Aus Sicht des Feeds ist der absolute Durchmesser des Hauptreflektors unbekannt, der 'scheinbare' Durchmesser bzw. der Oeffnungswinkel ist wie bereits erkannt relevant. Eine Linse (HF oder optisch) bildet einen definierten Bildausschnitt (scheinbarer Durchmesser) auf einen Sensor oder Film (Hohlleiter) ab. Genau wie ich ich als Fotograf zwischen Weitwinkel und Teleobjektiv waehlen kann, bildet eine Linse (je nach Design!) einen grossen Winkel (kleines f/D) oder kleinen Winkel (grosses f/D) ab. Eine Linse muss also zuerst mal die korrekten Winkelbeziehungen herstellen. Weiter sollte aber eine Linse moeglichst durchsichtig sein (wir wollen ja kein Licht bzw. HF verlieren). Optisch ist das einfach (durchgucken), bei 10 GHz muessen wir uns auf Messungen bzw. Herstellerangaben bei 10 GHz verlassen. HB9VQQ hat hier im Forum ja schon gezeigt, dass z.B. Nylon auf 10 GHz nicht wirklich Sinn macht, weil zu verlustreich. Teflon und Rexolite sind hier sehr gut.

Ein Fall, bei dem die Analogie zur optischen Fotografie zusammenbricht: probiere bei einem Primefokus von 0.375 f/D mal einen offenen Hohlleiter ganz ohne Linse, das sollte relativ gut gehen, da dieser von der Ausleuchtung da recht gut sein wird.

Please always keep in mind that the Pluto is a digital piece of equipment (key word: aliasing) and is 140 USD only.. there is a reason why real spectrum analysers are much more expensive. That said, once you recognize its limitations it is a great piece of hardware.

You should be easily triggering LEILA, so pay attention to your signal level and back off the power. WIth this kind of PA you should have a nice clean linear signal without splattering.. much appreciated!

If you do not DATV TX, 1m and 5-10W is plenty. I have 88cm here and never complained.

Just a general note on the mesh dish: they will be more lightweight but have little to no advantage in terms of windload. The holes are too small to actually be transparent to the wind but small enough to work for RF.

this one :

Sorry, the article has been written by somebody who has no clue:

1) the launcher itself (Atlas 541) performed flawless

2) the mars probe (cruise stage plus attached rover in lander shell) went through eclipse and went apparently in a safe mode due to conservatively set limits.

Our analysis of the signal received in Bochum suggests that Perseverance is being taken out of safe mode as we speak. The downlink datarate went up from 39 bits/s to 10kbit/s, a good sign!

maybe LNB getting hot?

Hallo Arne, laut Foto ist das ein ADF4351, der zwischen 0.7V und Vdd (wahrscheinlich 3.3V) pk-pk vertraegt. Der Abschlusswiderstand ist auf dem Foto nicht gut zu sehen, aber wenn deine Referenz unbelastet nicht mehr als 3V p-p macht bist du wohl sicher. Persoenlich wuerde ich ein Rechteck bevorzugen, da dies weniger Jitter (bzw. Phase Noise) hat, bei den Oszillatoren heisst das 'square wave' oder auch 'truncated sine' oder auch CMOS. Aber SInus geht auch.

Probably none.. just unprecise specs given by the manufacturer. As an example, if you have a 50 ohm output but don't load it at all with a terminator, you may have 3.3Vpp. But if you attach a 50 Ohms termination, the signal will be reduced to 50% just because of the resistive divider (50 Ohms in the source, 50 Ohms in the termination). So you end up with 1.65Vpp.

Next: what does the 32mA setting actually mean? We don't know, it could be just an internal current setting. 32mA vs. 16mA should be 6dB in power level.. it is not.

Next:

Quote from HB9VEQ

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

Fundamental power level means although you have a square wave they only quote the power in the 10 MHz component, not in all the harmonics. So again something to be corrected for. Why do they quote it that way? Unknown..

Bottom line: if you can measure it, do it. Adjust for the required PLUTO p-p level with a proper AC block and 50 ohms termination before you connect and enjoy.

Ah, that explains it and is actually very reasonable. Thanks for the solution!

DD0KP yes, the 10G lens has no effect (shouldn't). I8LYL former I0LYL I suspect either the adapter to be wonky or the way the N/SMA connectors were fixed to the reflector. It's just out of curiosity, the return loss and 'twist' at 2.4g looks fine to me.

pardon the question, but why do the two measurements differ so vastly? It is certainly fine for 2.4g but I don't understand the rest of the behaviour. Do you have pictures of the two setups?

The drive setting will only have an effect if the clock is terminated with 50 ohms.
Your dBm to Vpp conversion assumes sinewaves with a rms to peak (crest-)factor of 2xsqrt(2)=2.818. A squarewave has a crest factor of 1, so 1Vrms=2Vpp (p-p is 2x amplitude).

Hello and welcome to the forum!

Check the forum for 'LNB wobbling', I think yours is a classic example. Other might comment to this but I think this is due to a really cheap/bad crystal. It might go away with external injection but maybe not. Chances are that another LNB will have a better stability so given their low price, just dump this one for a better one and never look back.

73s Achim

DD1US so am just really lucky I am using it on 70cm (with 6x less drift), great!

The idea to correct the TX by the data obtained by locking the beacons is tempting, but cannot be done:

The RX correction (in a minimal system) corrects for the sum of LNB and Pluto instability. This cannot be disentangled. In addition, I think the Pluto does change its temperature (up) when transmitting. Not as hard as no PA is included but measureable.

I did the TCXO change myself as well and was surprised to see little effect, but this is because I use the AMSAT-DL upconverter V1 (70cm to 13cm) due to long and tiny cables here and the resulting TX frequency drift originates now in the upconverter LO, which is currently free-running and this does heat up on TX. As the upconverter has an external 10 MHz input, I already got myself a OCXO on Ebay (15 Eur) which should get rid of the drift. This will need to stay powered 24/7 though as warming up takes some time..

Hi Oliver,

actually if it weren't for the aluminium of the DK2DB filter, you can use it as a hammer.. it is big, heavy and well made. These type of filters (as duplexer variant) were used in many Packet Radio interlinks in DL (those were the times..).

CN0417: this one (and the G0MRF SDR driver amplifier) have integrated bandpass filters, so no additional filtering required. See a plot from the CN0417 datasheet here:

I would guess the bandpass from G0MRF looks similar as they are both SAW type filters.

73s Achim