Dish sizes

[abouttosnap]

Seen this come up a few times and thought this maybe useful for some. Seems to be some confusion on what is an 18" dish aka dish300. So just for the tally book if you have a dish500 it tant an 18" dish. :thumbsup: I knew the dimensions on the dish300, dish500 and dish1000 but I wasn't sure on the others in the list. Found this list out on the net so I stole it. :D Kudos to the author.

The old Superdish is 18"H and 36"W with a 2" mast in memory serves me right. I would have to dig mine back out to be sure. I do pretty good with a ruler until I have to count those little marks between the numbers. Reading a ruler when you ain't wrapped real tight like me is not an easy game ya know. lol


Mast Height Width
Dish 300 1 5/8" Look below
Dish 500 1 5/8" 22.5” 20"
Dish 500+ 1 5/8" 23.8” 30.9"
Dish 1000 1 5/8" 18" 23"
Dish 1000.2 1 5/8" 19" 24"
Dish 1000+ 1 5/8" 23.8” 30.9"

[jvvh5897]

Hum if that Dish 300 is the standard 18 inch dish, it is 18.25 by 19.5 with 22.5 degree offset angle and 11 inch focal length.
The Dish 500 is very similar but a little bigger--still 22.5 degree offset angle with focal length 12.33 inch and 20.5 by 22.35 inches.

[jvvh5897]

For the oval shaped dishes like the 300 and 500, there are a couple of equations to help you figure them out. Let D1 be the smaller of the two diameters and D2 be the larger, f the focal length and oa be the offset angle. Then D1=4 * f * tan(oa), D2 = D1/cos(oa) and the maximum depth d of the offset dish is d=(D1/4)*sin(oa). So, just measure the two diameters and oa = acos(D1/D2), then f=(D1/4)/tan(oa). Or you can use the max depth--about 2 inches for the 500 and 1.75 for the 300.

[SpaceCowboy]

I hope I am not hijacking some ones post. I have a question!
I have a Dish 500DP, it is sitting on the top of the garage and doing nothing! I would like to know if I can point it to another satellite? I am presently operating with a Dish500 and receiving 110-119.

[aidejr]

I hope I am not hijacking some ones post. I have a question!
I have a Dish 500DP, it is sitting on the top of the garage and doing nothing! I would like to know if I can point it to another satellite? I am presently operating with a Dish500 and receiving 110-119.
91 & 82 if you are in there foot print. I have seen it be said 100miles south of the border is the limit.

[jvvh5897]

Well, I'm not sure if my post will be hijack either but it was pointed out to me that the dish500 might be based on an elliptical equation rather than the parabola. So, I'm attaching a file where I analyse the ellipsoid, the hyperboloid and just for the heck of it the catinary eq, to see if and how one might use the eqs for satellite dishes. The result is that by and large it makes no diff what eq one uses, to make the shape act like a parabola it has to approximate a parabolic eq so closely that you might as well treat is as if it were a parabolic equation. I have some ray-trace images that show the ellipsoid does a nice job of getting a focus for lots of possible minor axes, but if the dish 500 is based on the ellipsoid then the focal length measured is not one of them--I measure 12 inch focal length where the parabolic equations suggest that it should be 12.33 inch and to get that smaller focal length you would have to use a=0.95c or so--the ellipsoid does a good job of approximating a parabola if a>c but it makes the spherical and coma distortions worse if a<c.

[jvvh5897]

I've figured out a way to get the offset angle of an elliptical dish from just the diameter along the line from LNB arm to top of dish and the max depth measured along that line, then with the offset angle one can use the same diagonal to figure the focal length. Using the equations, it looks like the Direct slimline has offset angle of 17.5 degrees with center line diameter of 22 inches and focal length of 17.5 inches. As the equations assume equation of parabola, that the eqs work means that the elliptical dishes are simply parabolic dishes and have little to do with the elliptical equation.