Circularly Polarized LNBF for Ku Band

[cawcaw]

This isn't exactly related to FTA, but I couldn't find a more appropriate topic to post this under, so please let me know if there's a better place to ask this!

I want to recreate the work here: Receiving Starlink satellite beacons - AMSAT-DL Forum. For my LNBF I currently have a SL1PLL v2 which seems to have pretty good performance from what I've been able to find and I've been able to see some beacons from Starlink (I think). However, from what I can find online, it seems like Starlink should be using LHCP or RHCP for their downlinks, so I wanted to try and find a circular KU feed to squeeze out 3 dB more signal from the beacons compared to linear. But it seems like these are much more rare than linear feeds, at least here in the US. The only cheapish consumer models I've been able to find have been the feeds from Digiwave such as DGL1189L and it's hard to find any performance information on these. In the EU, it seems like Inverto makes a feed that would be perfect for this here. But I can't find any place to get one of these in the US.

Does anyone have recommendations for where to look for KU circular LNBFs in the US? I've seen some people that converted a linear feed into a circular by making their own custom dielectric polarizer and inserting it in the waveguide of the feed but that seems difficult to get right. Would appreciate any advice!

 

[lost_mesa]

Dish Network had some circular polarized signals on Anik F3 at 119w in the 11,700 to 12,200 Mhz range. (I believe they are gone), so there were circular LNBFs available. I have one stored away somewhere. But, like the Inverto LNBF you linked to, it uses a dielectric resonate oscillators, which drift a lot. The Inverto spec is +/- 3 MHz of drift. That is a lot when you are looking for narrow telemetry beacons.

I think it is worth a try making a dielectric polarizer for something like the Bullseye LNBF, which is very stable. The most critical thing is finding the right material. On C Band I've made them out plastic cutting board material and strips of foil on a thin sheet of plastic, but nothing worked as well as the ones Titanium provides with his C Band feeds. But those are much too thick for Ku.

 

[SatPhreak]

Dish Network had some circular polarized signals on Anik F3 at 119w in the 11,700 to 12,200 Mhz range. (I believe they are gone), so there were circular LNBFs available. I have one stored away somewhere. But, like the Inverto LNBF you linked to, it uses a dielectric resonate oscillators, which drift a lot. The Inverto spec is +/- 3 MHz of drift. That is a lot when you are looking for narrow telemetry beacons.

I think it is worth a try making a dielectric polarizer for something like the Bullseye LNBF, which is very stable. The most critical thing is finding the right material. On C Band I've made them out plastic cutting board material and strips of foil on a thin sheet of plastic, but nothing worked as well as the ones Titanium provides with his C Band feeds. But those are much too thick for Ku.

When Dish was using those channels I used a 60E dish and made a dielectric slab out of an old credit card placed at 45 degrees. It worked wonders to get a signal. I couldn't get a signal without it.