Ku upgrade

[mreaves53]

This weekend I plan to install an Astrotel PM 93 C/Ku corotator. I have searched the internet for instillation instructions, but to no avail. I have found the page on determining the focal length of my dish. I have a 10' mesh disk with fairly small holes in the mesh (passed the pencil test I was told of). My C-band signal is 100 on VCII and between 50 - 70 quality rating on digital. My questions are;

1. Does anyone have any instructions on installing this corotator?

2. If not, where exactly do I measure to for the correct focal length?

3. This unit has a scalar ring, so which way do I orient the feed horn itself?

Any information will be greatly appreciated.

Thanks,

[wejones]

Originally Posted by mreaves53

This weekend I plan to install an Astrotel PM 93 C/Ku corotator. I have searched the internet for instillation instructions, but to no avail. I have found the page on determining the focal length of my dish. I have a 10' mesh disk with fairly small holes in the mesh (passed the pencil test I was told of). My C-band signal is 100 on VCII and between 50 - 70 quality rating on digital. My questions are;

1. Does anyone have any instructions on installing this corotator?

2. If not, where exactly do I measure to for the correct focal length?

3. This unit has a scalar ring, so which way do I orient the feed horn itself?

Any information will be greatly appreciated.

Thanks,

Re 1, sorry, not familiar with that feed.

Re 2, with the Chapparal corotor, I think you measure from the dish to about a quarter inch inside the throat of the tube that the scalar ring connects to. The ring itself usually can move forward or back depending on the F/D of the dish. The difficult thing on the feeds I'm familiar with it that you usually mount the feed via the rings, but there is usually no adjustment at the feed, only at the edge of the dish, which is hard to get to. May be different with your feed and dish though.
The focal length isn't so critical with C-band though, so it's probably best to set it up via measurement with the proper F/D setting, but then fine tune FL by moving the tube in and out slightly, while looking at Ku, since the scalar rings don't affect Ku so much.

Re 3, since you're using an analog receiver capable of controlling a polarotor, usually, they recommend mounting them at a 45 deg angle, ie up being at 10:30 on the clock, instead of straight up. This is because some receivers can only move the polarotor by a limited angle, and if you mount it at a 45 deg angle, you are only 45 deg from both polarities, and should be able to reach the proper angle from either polarization, but if you mounted it straight up, some receivers might not be able to move you 90 deg to get to the other polarity. With most receivers though, it doesn't really matter where you put it, since you can fine tune it with the receiver.

[elgemcdlf]

Originally Posted by mreaves53

This weekend I plan to install an Astrotel PM 93 C/Ku corotator. I have searched the internet for instillation instructions, but to no avail. I have found the page on determining the focal length of my dish. I have a 10' mesh disk with fairly small holes in the mesh (passed the pencil test I was told of). My C-band signal is 100 on VCII and between 50 - 70 quality rating on digital. My questions are;

1. Does anyone have any instructions on installing this corotator?

2. If not, where exactly do I measure to for the correct focal length?

3. This unit has a scalar ring, so which way do I orient the feed horn itself?

Any information will be greatly appreciated.

Thanks,

If you are only getting readings of 50-70 for quality on digital with a dish that size you are not properly aligned. My dish is only 8.5' and i am in the 80's and 90's for quality on the 922. Granted there are factors but I would consider 50-70 to be poor readings. You may want to work with dish alignment prior to disassembing a working system

[mreaves53]

Thanks for the heads up. I will do that this weekend and recheck my numbers. I believe part of my problem might be trees. I will check several different satellites.

Question. Since I am in East Central Alabama about half way between Birmingham and Atlanta, what is the southern most satellite I can receive? I understand east/west, but I am confused on North/South.

Thanks,

[elgemcdlf]

It will be the sat that is located closest to your longitude. I am at 87 degrees so my south sat just happens to be at 87. Sats generally are spaced 2 degrees apart. Longitude locations can be found at LyngSat - Lyngemark Satellite

[mreaves53]

So, when I aim the dish at the southern most satellite, the dish is pointing almost straight up. What do I exactly use on the dish to align the servo motor with?

Thanks,

[wejones]

Originally Posted by mreaves53

So, when I aim the dish at the southern most satellite, the dish is pointing almost straight up. What do I exactly use on the dish to align the servo motor with?

Thanks,

With a polarotor, you adjust it with your receiver. You don't have to climb up on a ladder. Since you have analog capability, I have always found that the best way to accurately set the polarity is to find an analog channel (preferably one without analog channels on the same channel on adjacent sats), and change the polarity until all traces of the analog signal dissappear. Mark that number, and continue changing in the same direction until you just start to see the channel again. Mark this number, then split the difference, and this will be a very accurate measurement of the opposite polarity. Then do the same thing on an analog channel of the opposite polarity. Ie you can get more accurate results tuning for nulls than tuning for maximum. With fewer and fewer analog channels, though, this technique's days are numbered.