can you do this? with 18 inch dish?

[tunamandude]

can you take an 18 inch dish,add extra lnb,mount it to the focal point of the 119 bird, run a seperate wire to your reciever with an a/b switch to use as a 101 and a 119 seperate connections,and use a non plus reciever so you can see the phoenix and the other locals on the 119? i know the eliptical dish gets the other satelittes what about this idea would it work? trying to use an 18 inch dish by adding extra lnbs with seperate connections?

[smack]

The answer, as presented, is correct. The "regular" dish's geomety makes it virtually impossible.

You be better off finding a scrap "regular" dish and either runing it through an A/B switch (non-plus IRDs) or getting a four-input, four-output (or more) "tone-enabled" multiswitch (if you have "plus" IRDs).

Good Luck, Happy New Year!

Scott

[tunamandude]

so, smack what you are saying is that the 18 inch dish is to small or not shaped right? i thought that if you had two lnb s like on the plus dish set up you could just mount those together on the 18 inch dish and get both the 101n and the 119. i also have a friend who has an old primstar dish thats like three feet round could i just use that dish then mount the lnbs the way that the eliptical dish has it set up and get both, or shoudl i just use two seperate dish one for each sat then use the a/b switch?

[smack]

That's correct. The dish is not shaped right to acommodate focusing the signal for two LNBs.

There's basically two dish shapes. Prime focus, which is a symmetrical parabola designed to gather the signal and focus it to one place (ONLY). The old "BUD" (Big Ugly Dish) 6',8',and 10'(or larger!) dishes were mostly this kind of dish...looks like someone lopped off the top of a ball.

Toroidal dishes, in general, are shaped like a section of a circular tube...sorta like someone cut a chunk of a car tire. The toridal dishes work the same as the prime focus, but because of the extended curve, can cover a wider sector of sky. The signal is focused in a pattern that would look like a semi-circular line in front of the dish. Because there are no reflections from the "sides" of the dish, toroidal dishes have a little less gain (signal concentration) than the Prime Focus dishes, but allows the one dish to service several satellites.

NOW...

The basic / traditional DSS/DTV dish is a varient of the prime focus dish...called an "offset prime focus". The main change of geometry is that the parabola has been "stretched" to allow the dish a more vertical mounting. The signal actually approaches the dish from an angle approximately three degrees higher than the apparent pointing angle. For example, if the setup / pointing screen says to set your elevation to 39 degrees, the signal is actually coming in from about 42 degrees. The actual pointing angle equates to your latitude...Chicago is at about 42 degrees latitude.

I'm guessing, but I believe DTV and others chose this design to help the dish shed snow/ice/rain...maybe they just think it looks cool...ya never know..

Anyway...offset or not, the signal is still being concentrated into one spot. Any signal hitting that dish from 18 degrees to the side is going to skip off without even a little concentration...for that matter, any signal from the outside of the ~ 3 degree sector that the dish is looking at is not going to make to the LNB.

The "Plus" dishes, which some of the IRDs (like RCA)call "oval" dishes but are sold as "elliptical dishes," are -probably- a variation of the toroidal dish type. They're more curved at the sides, and the curve of the dish is a little deeper.....allowing them to collect and concentrate the signal from a wider segment of the sky.

The geometry is still offset, but it's wider and "bent just right," by design, to cover four satellite slots (on the RCA version)...it will only acommodate three LNBs, but the mounting holes are there for an "either / or" selection of LNB placement.

Another factor is caused by the tilt of the Earth. As you move Westward, the apparent satellite positions are reduced in elevation. From Chicago, the 119 satellite appears about six degrees lower than the 101 satellite, making it necessary to "Tilt" or rotate around the Z axis to pick up both satellites. This is the third parameter a "Plus" IRD will provide when you plug in your location/zip code/Lat-long numbers. This is a CRITICAL setting....just ask anyone that's tried pointing the new dish....if the tilt is not set right, or the mounting is not plumb & level...it ain't gonna happen. The standard dish has no provision for "Tilt."

Bottom line: NO! you can't use a standard dish to collect and concentrate the signal from more than one satellite slot, especially one that's waaaaaaaaayyy over (and down) there in the 119 slot. The signals just bounce off to the side. You need a dish that's designed specifically for that purpose...the "Plus/Oval/Elliptical" dish.

BTW: If you look at most of the Satellite Remote trucks that the networks use, they usually have a huge pure toroidal dish so they can pump signal to a variety of satellites without re-aiming.

Hope this helps, Happy New Year!

(just another windy answer.....sorry)
Scott

[robinhood]

So smack,
What you are saying is that if or when you purchase a dish that has a dual LNB...that it should have a toroidal dish?

shaped approx...20"tall and 15"wide?

[smack]

Toroidal / elliptical dishes are wider than they are tall.

Did you mean a dual LNB (old dish)or double-dual LNB (new dish)?

The new Dish is (don't recall...) like 18H X 24W sideways oval.

I know there are some (large)commercial toroidal dishes that the Canadians might be able to use for multi-sat-single-dish installs. I don't know how far North you can go before you lose the Western Sats beacuse the signal is too weak. Probably a better bet to use multiple large dishes....

FWIW

Scott

[gsd103]

Smack that post should be archived. Along with your signal splitter post, hey how are your signal splitters working? ha ha
gsd103

[robinhood]

I was asking about the dual LNB older dish...

Thank you for answering my ???'s

I now see that I have the older dual LNB dish...

guess I will just hang another single LNB older dish to point the other way...thanks

[tunamandude]

hey smack,now i see why i cant use an 18 inch dish for getting both the 101 and 119,you have explained it well.i have a extra 18 inch dish and will try to find the 119 that way. thanks for your knowledge

[SMOKER]

Smack, I have several of the DISH duel duel LNB dishes. they appear to be closer to the 18 inch size. Will they hit both of the dss sats?

[smack]

I don't know this "Fer Sher," but I believe the DishNet500 dishes hit the 119 and the 110 slots.

IF that's true, then they probably wouldn't work for the 101 (primary DTV sat) and anything else. However, you may be able to use a standard dish for the 101, then use the Dish500 dishes for the 119 and 110 sats.

You'd probably have to replace the 110 LNB with one of the DTV "Special" LNBs (reduced bandwidth, single LNB)and use the "special" combiner to aggregate the two signals into a 4X4, tone-enabled multiswitch. There's some posts on the Satellite Installer's forum with ordering information and prices on the "special" stuff.

There might be an issue with setting the Tilt of the DishNet500 dish..but I'm pretty sure the value of the tilt would be consistant with the DTV sats, once the correct elevation is set.

Sorry I can't give you a solid answer, perhaps gsd103 has some additional information, he's better versed in the multi-dish scenarios & associated equipment.

Hope this helps, Top O' the New Year to ya!

Scott

[gsd103]

The positioning of the LNBs and geometry of the dish 500 will not let you receive 101 and 119. Now I have seen some info on repositioning the LNBs even on an 18" dish to recieve 101/119. That is two LNBs on an 18"dish sounds strange but this guy did it. So anything is possible if you have the know how.
gsd103

[SMOKER]

Thanks guys,But instead of playing with that in this weather, I think I'll wait until I trip over an eliptical DSS dish.Their far and few in between as turn ins right now , but after the hollidays, I might come across some.
On a second note ,is there any less rain fade if I use the 5th generation dish (duel-duel eliptical DSS) to hit the 101 over the 18 incher or is the focus just useing part of the surface.I dont have a big problem right now, I'm still getting low 90's in most snow stormes with 4 units on an 18 incher, but there are those times when i do get fade.. Don't want to LIVE WITH IT if I dont have to.

[Muggles]

You get a lot less rain fade, and signal fade, with the Eliptical dish. It picks up a lot more signal than the 18" pizza dish.