Norsat LNB Orientation

[tonydix]

I have just bought a Norsat 8515 LNB to bolt onto my Chapparel Feed horn. I notice by looking down the throat of the LNB that the small probe is off centre about 80% / 20 %.
The LNB will bolt onto the Feed horn in 2 possible orientations.

Which one is correct ?

Many thanks

Tony

 

[B.J.]

I have just bought a Norsat 8515 LNB to bolt onto my Chapparel Feed horn. I notice by looking down the throat of the LNB that the small probe is off centre about 80% / 20 %.
The LNB will bolt onto the Feed horn in 2 possible orientations.

Which one is correct ?

Many thanks

Tony

It was always my understanding that it didn't make a difference re to orientation, but I must admit that I never noticed that the probe wasn't centered. My 8115 LNB is also offset the same way you describe. I have an older version Norsat on my dish right now, and I'm not sure whether it's centered or not, but I'm guessing not. The actual sending probe in the feedhorn is perfectly centered, and the probe in my old CalAmp MiniMag LNB (ie with the built in elbow) is perfectly centered too.
I really don't think it makes any difference though. My thinking is that the position of the probe in the LNB is just the ideal spot for that LNB, regardless of whether the sending probe in the feedhorn is centered or not. On the other hand, it wouldn't hurt to try reversing it to make sure.

 

[sony1]

I have just bought a Norsat 8515 LNB to bolt onto my Chapparel Feed horn. I notice by looking down the throat of the LNB that the small probe is off centre about 80% / 20 %.
The LNB will bolt onto the Feed horn in 2 possible orientations.

Which one is correct ?

Many thanks

Tony

Anyone have an answer for this?

 

[comfrey]

It doesn't matter which way. Here is a link which explains the concept of the most efficient coupling to the waveguide.

Figure 3-42 view C 'loop coupling in a rectangular waveguide'.

Figure 3-41.—Probe coupling in a rectangular waveguide

 

[FaT Air]

I bet the orientations are 180 degrees from one another.

 

[madbull]

They can be mounted either way. I always mounted mine so the body of the 8515(long part where the coax feed comes out of) was cloest to the center of the scalar center. That way I could get my cover on the lnbs better.