"Dish 500" out of a True-Focus 1.8M?

[sforgue]

Hey Guys;
Short-time reader, first-time poster. I had a question about satellite stuff, and figured someone here would have the knowledge that I'm looking for.
I recently purchased a 1.8 meter True Focus dish from a friend who defected to D*. He was using the dish to get the E* 110W bird(s). That may seem like overkill, but up here in the Frozen North (ZIP 99705), a 1.0 meter is about the minimum to get anything. In fact, the wife and I are using a 1M dish just to get the 119 birds (AT120). What we would like to do (in the Spring, when we can get up on the roof) is use the 1.8M dish with either two LNBFs and some sort of bracketry, or the equivalent of a DPP Twin, so we can get both orbital positions with the one big dish. I don't know about that second option, as the 1.8M doesn't really look like it will be able to be skewed. Since my friend was just getting the one orbital position, there is just a single LNBF on the dish, and it doesn't look like it'll be real easy to attach an LNBF for the 110W satellites.
Can anyone help me out? (Oh, and you might need to dumb-it-down a little, as I'm only about two-months into the whole DBS thing).
Thanks in advance.

 

[Smith P.]

Not gonna work well - you'll need special bracket and two separate LNBFs, beacuse spacing betwen regular Dual or Quad ( 2 LNBFs block) maden for 20" dish.

 

[sforgue]

So, if I go with two separate LNBFs, I'll need to mount the second one in some sort of custom bracketry...
Is there any formula or rule-of-thumb as to where the second LNBF will need to go? Or do I just hang the thing off the side of the feed support, get a good signal on the 119W bird, and then just bend the custom bracket until I get the best possible signal from 110W? Or do I use the already-mounted LNBF to get 110, and the second, bracket-mounted LNBF gets aligned with 119?

 

[Smith P.]

Need to know focal lenght for the dish;
just measured: 20" have Lf=17"; 36" - 24"; 37" - 27";
for sure your spacing will be increased - I would install 119W as primary with higher signal level, then holding second LNBF in your hand, will find hot spot for 110W by checking signal meter or receiver; then will go for the bracket build.

 

[Anole]

slightly dumber version...

Yea, what he said....
I've actually done this before.
Aim dish at one of the birds, get max signal, lock everything down and leave it alone.
Use the meter described below - this'll give you some experience with it.

Get a $10-20 satellite signal meter and put it in-line with the new LNB.
(you'll need the LNB/meter connected to a receiver to power it)
Now, holding the new LNB beside the existing (mounted) LNB, move the new one around watching for signal.
Keep it about the same distance from the dish as the mounted one.
You'll want to hold the LNB beside the existing one and either somewhat higher or lower than the fixed one.
(depending on which side it's on)
To determine which side to put your new LNB, just think of the dish as a mirror that reflects the signal and reverses where it sees the satellites.
So, the 119 bird is more west, but the 119 LNB is mounted more east (and vice versa)
(discussions using the words left or right, are confusing, as the L/R is determined by whether you are standing in front or behind the dish)

Once you find where the new LNB needs to be, build a bracket to hold it.
Scan through the Dish or DirecTV satellite forums here, and you'll see some amazingly creative ideas folks have come up with to solve this very problem.

Welcome to the forum.

 

[sforgue]

Thanks for the info, guys. I guess my next purchase will be a new LNBF and a signal meter. I've got a couple of friends that are pretty handy with hunks of aluminum, so I should be able to figure out something that'll work.
Thanks again for the info.

 

[lousatellite]

We have been using a 1.8m True focus dish with a two LNB set up to create a dish 500 for over two years now. And we also live and install in the 99705 area. It works good, alignment is a bitt tricky and you will need to make a bracket for it to work. There is no need to scew the dish, you scew the bracket.

 

[sforgue]

Lou;
When you did the two-LNB setup, did you use two regular-old Dish LNBs? When I bought the dish, it had a DirecTV LNB installed on it, even though my friend had been using it for Dish. Also, can I buy (off eBay, or Sadoun, etc.) a Twin LNB, and separate the housing and take the two LNBs out and mount them separately?

 

[Mr Tony]

no. The Twin LNB is welded together so if you crack off the housing, its still one giant LNB

 

[Anole]

how to connect it all together

As said, you'll need two independent LNBs.
Depending on which type they are, and how many satellite receivers you want to hook up to, you'll need different switches:

1). for DirecTV LNBs or Dish Legacy LNBs (electrically interchangable)
...a) for one or two receivers = one or two SW21 switches
...b) for more receivers, we will discuss it with you.

2). for Dish brand Dish-Pro LNBs
...a) for one or two receivers = one or two DP21 switches
...b) for up to four receivers = one DP34 switch

There were some facts not included above, so post your intentions and we'll be able to make sure you don't wind up with any surprises.

Method 2b above is my favorite for simplicity, cost, and expandability.
Method 1a may be sufficient for your needs.

 

[sforgue]

Right now, we're just running two of the DP311 receivers. Once we can get reception from 110W, we'll probably add some HD programming. But, we'll probably never have more than two receivers.
For simplicity's sake, we'll probably (at first) go with option 1a.
Back to opening-up-an-LNB. Does anybody have any pictures of what's inside of the different types of LNBs? I'd be interested in seeing exactly what's inside of those things.

 

[Mr Tony]

Here is what an old Stacked LNB looks like with the cover off

The newer ones dont have the "pregnancy" at the bottom

 

[whatchel1]

Display a picture

We have been using a 1.8m True focus dish with a two LNB set up to create a dish 500 for over two years now. And we also live and install in the 99705 area. It works good, alignment is a bitt tricky and you will need to make a bracket for it to work. There is no need to scew the dish, you scew the bracket.

If you can why don't you display a pict for your friend as to how you did it up there.

 

[sforgue]

Thanks to everyone who has responded with info so far. I've got some more information about the dish: F/D ratio=0.610; focal length=43.92"; angle of offset=22.3 degrees. With the new information, can someone tell me roughly where the second LNB would need to be located?

 

[Smith P.]

A distance between centre points of two LNBF: d = 43.92" x cos(9°)

 

[sforgue]

Double-check my math here: (43.92) X cos(9) = approx 6.9"...
And then I'll have to either raise or lower the second LNB to accomplish the "skew".

 

[Smith P.]

I did mistake - should be SIN(), but you did it right !

If you'll make clamps around both LNBF's neck, like that:

-^--------^-
 0        0
-v--------v-

then you could rotate it up/down when checking for max signal.

 

[Anole]

narrowing down the options...

Yea, I was doin' the math and noticed the error, too.

Was discussing this at lunch with a buddy, and realized that it's not hard to explain which side the new LNB needs to be and whether higher or lower than the fixed one.
(You already have approx distance - nothing is perfect, so do tune for maximum smoke)

Let me see if I can say this right.
I'll reread my post and verify, or if I totally screw up, someone will correct me.

....since you are located west of the 119 (most west) bird....
(this is not correct for people in other places!)

If the fixed LNB is aimed at 119:
the 2nd lnb (110) will be to the west side and above the first

If the fixed LNB is aimed at 110:
the 2nd lnb (119) will be east side and below the first

(the higher the LNB is placed in front of the dish, the lower it points in the sky)
Someone double check me, but that all seems right.

Hey, at least it'll get you in to the correct quadrant.
edit: stupid me! Your skew angle is about -14 degrees!
Just looked up your zip on a sat finder program. That was easy.
...assuming you are at about: Latitude 64° 46.830'N & Longitude 147° 22.164'W
.

 

[sforgue]

Anole;
So a skew of -14 degrees means that the second LNB would need to be 14 degrees below the fixed LNB (assuming the fixed LNB is aimed at 110)?
That is correct for the Lat/Long here.

 

[Anole]

or so the theory goes...

Looks good on paper. :up

Always a chance I am mistaken.
Lots of opportunities for others to call me on it.
Give it a try and prove me wrong.

Never did like pure science. I prefer applied science.
So, apply the numbers/angles and report what you get.
And remember, make your mount adjustable, and always tune for maximum smoke!

Kudos to Smith, P for the lesson in optics (distance calculation).
The stuff I posted is just common sense.