Dielektrische Linse für POTY und BaMaTech Feed

Quote from DL5LF

This lens from a vendor of a POTY kit

... looks like a 3D-printed lens. Do yo knwo what kind of filament was used?

I tried different filament, PLA works fine.

... and, did you adjust the focuspoint after adding the lense?

73s de Robert

Quote from DH2VA

PLA (3D Druck Plastik) ist für die dielektrische Linse ungeeignet.

Hm, kann ich nicht bestätigen. Hab hier verschiedne Filamente probiert, nur mit PLA komme ich auf die gleichen Werte die das Original Feed auch liefert. Schon interessant.

Yes, it is printed and came with the kit.

In a first step I tested the assembled POTY with LNB on Astra TV Sat and was not able to achieve reception. After removing the lense reception was normal. Focus point does not have such a huge impact between signal there and nothing.

Will do some tests the next days with some other lens from commercial LNB, stay tuned.

Frank

Black PLA loaded with carbon perhaps?

Black, yes, carbon maybe as pigment for black colour.

No warming up in the microwave oven ...

Frank, whats the f/D of your dish? Maybe the wrong lense.

I can confirm the results from @DG7YEO (beginning of this thred), that venton lens gives some 5dB better rx results compared with open feed (POTY). Readout from SDR-Console + pluto SDR.

For the records: The black printed lens is not as bad as experienced in my first steps, but it gives some -2dB compared with open feed.

My dish is 40cm TV offset type. Figured a lot with the focus, but seems to be the same for both lens.

BTW: My rain-cap (Quarkdose) as mentioned in "Wetterschutz" thread does not introduce noticeable attenuation.

@DD4YR: I presume the lens is designed for TV offset dish and I guess that all these TV offset antennas have almost the same f/D.

Hi,

A new batch of Venton LMBs arrived and UV sterilized… to avoid COVID-19.

Then on the operation table two lovely pieces of plastic rings. My question is what make this design to over perform all the anther lenses?

Here actual in Ebay is a seller with I think maybe the last possible chance to get Venton single EXL-S for a fair price. Ver good for portable equiptment or just to use the lens. Red Rocket and Venton EXL-S are discontiued!!!!

https://www.ebay.de/itm/Maximu…ksid=p2060353.m1438.l2649

Hi Heiner,

besides the lens, is this a PLL LB with no wobble and thus suitable for NB operation ?

Kind regards

Matthias

http://www.dd1us.de

Matthias, its more the lens. My Megasat Diavolo is better, I´m using this lnb with the Venton lens.

73 Guntram oe9dgv

As I red this morning from Andreas DL5CN he had ask the seller.. This is no Venton. The advertisement is wrong. Sorry.

Thanks and regards

Matthias

http://www.dd1us.de

Got those maximum LNBs last year for 5EUR. Just for the lens. It's a non PLL LNB.

Hallo,

I can confirm, the Maximum LNBs include DROs.
What to do? Send it back or keep the lenses?

I added a patch to a Megasat Twin Daivolo. The Waveguide is nearly the same like the rockets. This could be an alternative.

The Horn isn't very deep. It can be cutted with a lathe. Take care not to get in trouble with the cutter holder.
Then stick the waveguide to a wood core for further work.

No idea how the case will look like. And how to mount it. Depends on the dish and the LNB holder.

I didn't expect a cylindrical wave guide. If there will be further production, wie don't need the rockets anymore.

73
Andreas

DL5CN Andreas, if you shorten the lnb plastic, you can use it again. And if you are using the Opticum 80cm dish for 20€ it will fit.

Quote from DL5CN:

What to do? Send it back or keep the lenses?

Keep the lenses and send it back. Good idea, but I think the seller would not like this very much. But you can give it a try anyway.

No: Just keep the lenses as I did. I think it's worth to keep them.

Hallo zusammen,

es wurde ja nun jede Menge über dielektrische Linsen geschrieben, aber ich vermisse dennoch die Theorie dazu. Wie lässt sich eine solche Linse berechnen, wenn sie bestimmte Eigenschaften haben soll?

Die Linsen der handelsüblichen LNBs wurden sicher passend für die handelsüblichen Offset Spiegel konstruiert, sodass diese Spiegel weitgehend optimal ausgeleuchtet werden.

Mein 1,2m Gibertini Offset bringt mit dem POTY und einer Linse eines Rocket LNBs optimale Performance. Wenn ich dagegen dieses POTY in den 2m Siemens Primefokus, der an unserem Clubheim steht, schraube, dann ist der Empfang deutlich schlechter, obwohl der Spiegel ja deutlich größer ist. Der Grund ist offensichtlich das andere f/D-Verhältnis.

Mein Gibertini hat ein f/D von 0,66 und der Siemens Primefokus nur 0,375. Das heißt, dass das LNB im Gibertini nur einen Ausleuchtwinkel von 80 Grad haben muss, um ihn voll auszuleuchten, der Siemens Spiegel benötigt jedoch dafür ca. 130 Grad. Im Umkehrschluss beseutet dies, dass von 2m Durchmesser ein Großteil für den Empfang gar nicht genutzt wird.

Daher nochmal die konkrete Frage: hat jemand eine Ahnung, wie eine Linse zu berechnen ist, die einen Ausleuchtwinkel von >= 130 Grad erzeugt? Darüberhinaus wäre noch wissenswert, aus werchem Material diese sein sollte und vor allem, wo dieses Material zu bekommen ist?

Vy73 de Achim, DL3RY