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.

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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.

Hello my friends. Taking the discussion, I would like to ask a question. I am building a helical antenna for Rx, which will be connected directly to the LNB by an SMA cable. Usually with waveguides, I use a polariser. But on coaxial cables? Will my LNB be able to receive the signal in RHCP?

The problem with a circularly polarized antenna is that your receiver will now pick up both the V and H poles of the satellite transponder, and all of the other transponders that the antenna can see.

If your antenna is really high gain, them it will see only a few additional satellites. My general guideline is to double the antenna gain with the goal of decreasing the beam width of the bare LNB. You can them see half of the interfering satellites/transmitters as the bare LNB sees. But since you are circularly polarized both the horizontal and vertical poles of all the in-view satellites become interferers.

The doubling of interferers in a smaller swath of sky should produce the same SNR as a lower gain bare LNB. But the benefit you have is that no skew adjustment is required for circularly polarized antennas.

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I’m currently still using the Maverick and it’s been doing good I’ll update the post with the data from the tuner tab when I get on my pc

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With the new frequency and beam type in the americas, is it still possible to use the LNB 18 with dish? And what should my settings be? I just realized I was trying to use the old settings from before the freq changed to 12.

By new do you mean the frequency that was changed in January?

What is an LNB 18?

Sorry! Yes, the freq change in Jan.

And it’s a circ rather than linear pol that comes with the directv dishes. I had seen that some people COULD use them with the old freq with adjustment for offset etc.

Just wondering what the offset would be if I attempted to use that one with the dish

Currently, dish is pointed correctly as far as I can tell. Within less than .5 of a degree on every axis.
Bias-T etc shows green.

[ OK ] Bias-T is configured on: 0xbb
[ OK ] Bias-T voltage is set to 14.2V
[ OK ] LNB power is configured on
[ OK ] LNB detected, normal current flow: 0x23
[ OK ] Bias-T Voltage normal

Beam type 164

LO is set to single at 10.750

But I’m getting NOTHING on the status page for the tuner, no matter how I tweak the freq within what I THOUGHT would be correct…

Based on the old info here and in the “manual” I was changing by -.05 from 12.1032. The LNB 18 has a LO of 11.250 so the old settings said 11.4024 for it, from the “nominal” of 11.9024. So for the 12.1032 freq I have it set to 12.0382 or 12.0532

No SDR. Just the Dreamcatcher 3.05, skylark 5.8. Worked “ok” with the LNB that came with it, but I wanted to see if I could get the dish to work

How far from the nominal frequency are you tuning? A normal LNB can have offset as high as 1 MHz.

Do you have an SDR? One of the $30 dongles?

I have used the lnb 18 circular lnb , and you are on the right track to change the frequency. The 12.1032 assumes a 10.750 LO offset. Since the lnb 18 circular has 11.250 you must adjust by the 0.500 GHz difference. So like your example, you might try a custom frequency of 12.1032 minus 0.500 = 11.6032

I don’t have the circular lnb installed right now… so I am going by memory. It might be you have adjust to a custom frequency the other way… 12.1032 plus 0.500

Expect a good SNR with the 18 inch dish in the range of -8(dB) or better.

Edit: make sure in your tuner selection that Maverick 1 lnb is selected.

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