Corotor II Plus Assembly/Install Questions

[jnastasi]

Finally got my Corotor II Plus and Norsat LNBs in yesterday. I was noticing that, per the forums here, it really doesn't matter how you orient the LNBs on the feed. Also noticed in the Chaparral instructions that you should take the clear piece of cellophane off the Ku-band LNB waveguide. Everything's cool there.

One thing that was a little unclear ... the Chaparrel came with two C-band gaskets, and the Norsat 8115 came with one as well. Chap manual states that, if you're not using the elbow, use both gaskets.

So ... when I connected the 8115 straight on to the feed, I put one gasket on the feed side, left the Norsat gasket on the LNB, and tightened it down. Is this correct? Seems like you should only use 1 gasket total, instead of two, but the Chap manual is a little unclear about this. And if you do use two ... do you just butt them up against each other like I did, place one inside the other, or just what?

TIA to anyone more experienced with this who can chime in.

 

[zaxxon]

When I changed mine I only used one gasket, the instructions didn't seem very clear to me. I don't know why you need two gaskets.

Mine works fine

 

[B.J.]

Finally got my Corotor II Plus and Norsat LNBs in yesterday. I was noticing that, per the forums here, it really doesn't matter how you orient the LNBs on the feed.

With most receivers it doesn't matter. The Corotor instructions suggest orienting it at pretty much of a 45 deg angle, mainly because if you have a receiver which has a limit with respect to range in polarity adjustment, that you don't want the limit real close to one of your two H/V settings. For example, if your limit is right at V, and you're trying to fine tune polarity, you could get in a situation where you'd have to rotate the probe 180 deg to move 1 degree. I did have this happen to me once with an old receiver. If you orient the feed at 45 deg, ie at the 10:30 position, there is not likely to be such a problem.
One other situation where orientation used to be important, is if you have a receiver that thinks that it knows which pre-programmed sats were which polarity. Once, back in the analog days, I installed my feed 90 deg off the recommended orientation, then went on to "find" all the satellites. It was one royal pain, in that when I'd go to each satellite, the receiver thought that it knew what polarity it should have, and I'd get zero signal on all channels, unless I'd first save the sat at some random, wrong position, reverse the polarity, then search for the sat, and re-save it. After spending about 2 hours programming in about 3 or 4 sats this way, I gave up, went outside, rotated the darn feed 90 deg, came back in, and did the whole arc in less time than it took me to do 3 or 4 sats. In today's digital world, I don't think that this would be an issue anymore.

Also noticed in the Chaparral instructions that you should take the clear piece of cellophane off the Ku-band LNB waveguide. Everything's cool there.

I've installed lnbs with and without the clear film, and have never noticed a difference. I've heard that some brands recommend taking it off, and some recommend leaving it on.

One thing that was a little unclear ... the Chaparrel came with two C-band gaskets, and the Norsat 8115 came with one as well. Chap manual states that, if you're not using the elbow, use both gaskets...
..
So ... when I connected the 8115 straight on to the feed, I put one gasket on the feed side, left the Norsat gasket on the LNB, and tightened it down. Is this correct? Seems like you should only use 1 gasket total, instead of two,...
...

I'm a bit confused by this. Maybe I don't understand what you're saying, but I don't think you should ever put two gaskets on one joint. Basically, you want the metal surfaces to make solid contact, and 2 gaskets might prevent that. I have unused gaskets floating through my desk drawer. I have never used more than one gasket on a joint. Discontinuities in the waveguide surface disrupts the rf traveling along the skin of the metal, so you don't want any gaps at connections.

EDIT: It just occurred to me that it might depend upon whether you were mating up two surfaces both with groves, vs 2 surfaces one with a grove and one flat, without a groove. I can't remember off hand what the situation is there with and without the elbows. But bottom line, you want the gasket to deform, but you also want the metal surfaces to come together.

 

[Lynskyn]

I think they say to use 2 gaskets because both the feed flange and the LNB flange have a gasket recess and the elbow side that goes to the feed does not.

 

[jnastasi]

Thanks for the feedback guys. I did notice that there are two grooves for the gaskets ... one on the feed side and one on the LNB. While it seems a little weird to mate a gasket up against another gasket, I'm definitely getting metal on metal upon tightening things down. Think I'll just leave everything as is and run with it.

On a humorous note ... I set out to calculate the f/D yesterday and, upon measuring the diameter, found out our 12 foot dish is actually ... 120 inches! Boy it sure seems bigger up in the air.

 

[Lak7]

found out our 12 foot dish is actually ... 120 inches!

Up here, we call that 10 feet.

 

[jnastasi]

Up here, we call that 10 feet.

Yah ... I'm having the same problem down here as well.