Circularly polarized LNB for reception?


Looks like BSS/circular is outside of the 11.9 GHz of our carrier on SES-2.


Excellent point. It is always encouraging to find reasons for observed problems. I wonder how many linear LNBs are out of the frequency range? This is a good point to add to the user’s guide for those folks using their FTA systems so they use the correct LNB. I never thought to look at this issue.

Off hand, do you know if some linear LNBs don’t cover 11.9 GHz? Ken


It’s hard to say. Sometimes components are sold for specific services, which may be entirely within parts of high band and low band.


I guess the best way to describe the LNB would be a linear including 11.9 GHz operating frequency with a specific frequency stability. This may vary with other sat beams. Ken


Ken, from your lnb spec’s. If you connected to either port 2 or 4,
then your are on the circular detector (antenna) elements and processing the the lnbf
conversion at the ‘high’ local oscillator.

Thus… if you try to use port 2 or 4. you will need to use the custom frequency selector to get your
signal into the Dreamcatcher range… So set it to 11402.4. and after the ‘apply’, cycle power on/off to get it set correctly.

You can ignore the RHCP/LHCP designation since you will be matching a linear signal to the circular receive elements, as @Tysonpower mentioned, expect a 3 dB loss compared to linear receive elements.

there could be some ‘detuning’ between 11.7-12.2 and 12.2-12.7 GHz. but I doubt it is measurable.


In total there is a 6dB loss when receiving directly with an LNB (without dish). 3dB is polarization loss and another 3dB can be attributed to the additional transmitters find from seeing both H and V poles.


I’ll try this on Sunday when I get home to see what happens. Stand by - - Ken :sunglasses:


You’ll definitely need to add a cone for additional gain, otherwise it won’t work at all. The LNB I was using was an old Echo 2800 with an LO of 10750 MHz. It was basically a drop-in replacement for the MK1.