Angle of dish arm mean anything ?

sv1000 · #1 (**permalink**) 01-04-2007, 09:10 PM

Someone said that the angle of the arm (that goes from the dish to the LNB) to horizontal is in fact the Elevation angle. It doesn't look true to me or if it is true, its true only for specific dish designs / manufacturers and not across the board (though it would be great if it was) ?

Anyone know of sure ?

wejones · #2 (**permalink**) 01-05-2007, 10:22 AM

Quote:

Originally Posted by sv1000

Someone said that the angle of the arm (that goes from the dish to the LNB) to horizontal is in fact the Elevation angle. It doesn't look true to me or if it is true, its true only for specific dish designs / manufacturers and not across the board (though it would be great if it was) ?

Anyone know of sure ?

It is definately not true for the dishes I've looked at. I think that in some cases it might be close, mainly because they try to position the LNBF so that the true center of the parabolic dish is just off the lower edge of the dish, so that the line between the lower edge of the dish to the lnbf is usually close to aiming at the sat, however in the dishes I have looked at, this is not the case. I forget exactly, but it was off by 5 or 10 degrees I think. I have it written down somewhere. I'll see if I can find my notes.

be236 · #3 (**permalink**) 01-05-2007, 12:20 PM

Also... I was wondering... doesnt the LNB arm and LNB itself block some of the signal from the sat (albeit slightly?)...

wejones · #4 (**permalink**) 01-05-2007, 03:27 PM

Quote:

Originally Posted by be236

Also... I was wondering... doesnt the LNB arm and LNB itself block some of the signal from the sat (albeit slightly?)...

No, that's the reason the center of the parabola is slightly below the bottom of the dish. Ie the line going from the sat through the lnbf really misses the dish by a little bit. Now with a prime focus dish, yes the feedhorn does block some of the signal.

be236 · #5 (**permalink**) 01-05-2007, 04:15 PM

Really? I didnt realize that.. so you're saying the way the Ku 80cm dish works given a clear open southern sky is that a sat signal will get beamed into all parts of the dish and the LNB/arm wont catch/block any of this signal due to the parabolic curvature of the dish? cool!

N4ST · #6 (**permalink**) 01-06-2007, 08:11 AM

Quote:

Originally Posted by sv1000

Someone said that the angle of the arm (that goes from the dish to the LNB) to horizontal is in fact the Elevation angle...

As was pointed out below, that ain't true. I use one dish that the angle of the LNB arm is 17.8° lower than the look direction of the dish. I can lay a digital level on the LNB arm, applying that offset, and get the elevation almost perfect (even if my mounting pole isn't plumb).

wejones · #7 (**permalink**) 01-06-2007, 08:23 AM

Quote:

Originally Posted by N4ST

...... I can lay a digital level on the LNB arm, applying that offset, and get the elevation almost perfect (even if my mounting pole isn't plumb).

I'm curious.... what brand digital level did you find? I've looked in places like Home Depot, and in tool catalogs, and haven't been able to locate one. I think I've seen some that just measure to the nearest degree, but it sounds like yours gives tenths of a degree. Just curious. Also, how expensive are they? Thanks.

N4ST · #8 (**permalink**) 01-06-2007, 11:40 PM

Wejones,

I have a SPI-TRONIC Pro-360. Kinda pricey at $200, but you can pay a lot more for this type of device. I've had mine for about 8-years and it works perfectly. They have a manual calibration process that can keep the accuracy to 0.1° For $350, you can get the Pro-3600 which will give you 0.01° resolution!

Geneva Gage - Electronic Clinometers

Another handy feature is the "Hold". You can sight along the top of the level at the tree line (or near by buildings) and press the "Hold" button to give you a readout out the elevation angle. I live in a clearing in the woods and its handy for figuring out where to locate a dish to clear the trees. :-)

I believe Sears carries this same level as:
Macklanburg-Duncan Electronic Digital Protractor

Sears item #00940195000 Mfr. model #09424516

wejones · #9 (**permalink**) 01-07-2007, 09:50 AM

Quote:

Originally Posted by N4ST

Wejones,

I have a SPI-TRONIC Pro-360. Kinda pricey at $200, but you can pay a lot more for this type of device. I've had mine for about 8-years and it works perfectly. They have a manual calibration process that can keep the accuracy to 0.1° For $350, you can get the Pro-3600 which will give you 0.01° resolution!

Geneva Gage - Electronic Clinometers

Another handy feature is the "Hold". You can sight along the top of the level at the tree line (or near by buildings) and press the "Hold" button to give you a readout out the elevation angle. I live in a clearing in the woods and its handy for figuring out where to locate a dish to clear the trees. :-)

I believe Sears carries this same level as:
Macklanburg-Duncan Electronic Digital Protractor

Sears item #00940195000 Mfr. model #09424516

THANKS! I have GOT to get me one of those things. Last time I checked up on those things, they weren't nearly that accurate. Too bad I didn't have these links a month ago. But the next time my wife buys something, I think one of these gadgets will be headed this way too.

Thanks.