7.5 mesh setup

[Pi314]

Setting up 7.5 mesh dish with BSC-621 combo LNB. The dish will be non-motorized and fixed on one bird until I find the optimal focal point and fine tune the position of the LNB. Probably use 97w to test with?


After the pole is installed, I will place the mount on the pole and calculate elevation and declination. My understanding is that you adjust elevation according to your latitude (43 latitude for me).


I used the calculator and chart at http://www.bigdish.info/mainten/align.html. According to their chart I will use a 5.89 degree declination?


I will be using an angle meter from Home Depot to measure. I found an old installation guide for the “Perfect 10” mesh dish I am using as a reference (see pics).


Any suggestions?


Thanks,
Pi

 

[FaT Air]

http://www.geo-orbit.org/sizepgs/decchartp.html says the 'Modified Declination" angle is 5.96 (usually referenced here) .07 difference, probably too small to be measurable. Then set the polar axis angle to your Latitude. Find your closest to "true south" satellite - Adjust the 'twist of the mount, on the pole, and fine tune the polar axis angle for max. Then adjust the Azimuth as you move the dish, with the actuator, to the end of the arc. (do not adjust polar elevation unless you're looking at your "true south" satellite) Only use the actuator and Azimuth adjustments to peak "Q".
I find it easier to adjust the LNBF when the dish is aimed closer to the horizon, as there you're not 'hanging' above the dish itself. Then one can fine tune the tune up of the dish tracking for optimum.
With a Dual band LNBF, think you'll find that maximization occurs in 2 different focal lengths. So you can max one and have just OK on the other. Or 'splitting the difference' may work well for you. Or it may work out that both focus at the same point. Results have varied.
Attached: the angles, in a picture, for your initial 'south' settings.
Tune up on C band first. [More forgiving] Then proceed to Ku after the arc is tracking on C.
Ku adjustments are much smaller than Ku.

 

[Pi314]

Very helpfulinformation, thanks. To center the LNB to the center of the dish, maybeuse some sort of laser pointer(s) gently taped to the inside throat of LNB?
If I need tocalculate focal length I can use f= D²/16d (D=diameter, d=depth). The JPG of themanual I have is difficult to read, but from what I can read I will measurefrom the “dish centerplate to the inner ring face of the feed horn”. I am usinga BSC-621 LNB, so would this be to the face of the LNB?
Thanks,
Pi

 

[primestar31]

Here's the link to the full-size entire Perfect 10 assembly manual I uploaded last year, it's for ALL their sizes, so follow the part for a 7.5': http://www.satelliteguys.us/downloads.php?do=file&id=329

I installed a 10' one, and found out that you NEED to follow their instructions EXACTLY! Do not assemble the entire dish, completely crank down every bolt, and then put it on the mount. Like you would pretty much every other dish. If you DO, it won't pass the string test, and you won't get the lnb/feedhorn centered right. I found that all out the hard way.

Get it on the mount and passing the string test, THEN worry about centering the feedhorn, and getting it flat in plane with the dish. I used a laser level for this, and it makes all the difference.

IF you follow their assembly instructions exactly, it should all come out PERFECT!

 

[Pi314]

Thanks for the manual, clear and easy to read! String test, stretch two pieces of string across the diameter of the dish?

 

[FaT Air]

String test: stretched across the face at 90° to each other. And again, to confirm, repeated at a 45° from where the first test was performed. The strings should just touch where they cross at the center of the dish.