Circularly polarized LNB for reception?


#21

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


#22

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


#23

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


#24

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


#25

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.


#26

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.


#27

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


#28

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.