triple LNB on a six foot dish

[MikeInAlaska]

Hello, long time.. no post.

I am wanting to put three LNB on my six foot dish due to weak signals here in Alaska. My switch is connected to a 6 foot dish on 129 and I get signals like 75-80, and connected to a small dish on 110 and 119 and I get signals like 20-30 very typically.

I can certainly rig up a curved bar to put all the LNB on the big dish, but how in the world do I figure even starting close positions to try for the signals?

Thanks for your insight!
Mike in Alaska

 

[Mr Tony]

honestly when dealing with a large dish like that it is hit and missas to where exactly to put the LNB

 

[TheKrell]

There must be a way to calculate placement given the focal length of the dish.

 

[boba]

There must be a way to calculate placement given the focal length of the dish.

Prime focus is easy to calculate but offsets get much harder.

 

[MikeInAlaska]

I have an offset LNB for 110 on my 119 dish. That dish is quite a bit smaller, I wonder if I can linearly scale the measurements in a similar fashion and get ..close. How would I ever know though? Should I have a dish box and a small TV out there on an extension cord watching the "point dish" screen?

 

[TheKrell]

Yes. If you don't have one of those fancy stand-alone meters, a TV and receiver should do the trick. Along with a mounting rail for the LNBs set to the right skew for your location.

 

[Jim5506]

This idea will not work.

By moving the center lnb to the prime focus of the large dish, you also move the other 2 lnb's foci much nearer, i.e. the three will probably see more like a 5 degree maybe less spread of the sky instead of the 10 degree spread necessary to focus all three lnb's on the correct satellite.

If you were to spread the lnb's out so the two outer ones were at the appropriate distance to be in the focal spots for 110 and 129, the dish itself is not designed to service lnb's that far from its prime focus.

This is why persons in Puerto Rico, Alaska and Hawaii (really anyone outside CONUS) must either use the dishes provided by Dish Network or they have to go to separate dishes for each satellite.

 

[stvcmty]

Do you have 3 physically separate LNBF’s for 129, 119, and 110?

If you have separate LNBF’s and run a coax from each LNBF into a Dish switch you can probably make this work. If you have a single assembly with 3 feed horns the problem pointed out in post #7 comes up.

If I were you, I would aim my big dish at 119 and put the LNBF for 119 in the center of the dish. Then I would find 110 and put a LNBF there. 119-110=9; 129-119=10, so if you find 119 you will have a rough idea how far in the opposite direction to go to find 129.

 

[MikeInAlaska]

I would use separate LNB. I would point the big dish at 119 (or 110) and use a side LNB for the other sat. That type of setup has worked for me for years with this smaller dish as the attached image shows. I am just not sure where to start with the placement on the big dish. I guess I will try a starting position by linearly scaling up the measurements.. since the satellite spatial separation is the same.

 

[DishSubLA]

Is having separate parabolic reflectors (dish) for each sat out of the question? That would be easiest and just run each line into a Dish multi-switch, as suggested in an earlier post. You can get that up and running in short time and with the strength of signal you require.

 

[MikeInAlaska]

It is not completely out of the question, but multiple six foot dishes is a pretty serious yard addition.

 

[boba]

Are you using LEGACY or DISH PRO LNBs?

 

[MikeInAlaska]

it has been a while and I do not recall, and since we tore off the plastic cases, I do not recall what they are! I have 3 (110,119,129) running into a DPP33, does that tell you what kind?

 

[Magic Static]

What kind of 6' dish? Prime focus or offset? The problem with using those LNBFs are they were designed for the smaller dish. The scalar feed configuration will not let them see the full size of the 6' dish, so it may not perform better than 1.2m , 4' dish. You don't have to worry about skew because of the circular polarization, but getting circular lnbs for the bigger dish might be a problem. While you should be able to set something up like you envisioned, it will not work as well as having three separate dishes of course. And 3 dishes would be the easiest thing to do.

 

[TheKrell]

it has been a while and I do not recall, and since we tore off the plastic cases, I do not recall what they are! I have 3 (110,119,129) running into a DPP33, does that tell you what kind?

Yup; DP LNBs.

 

[MikeInAlaska]

> Yup; DP LNBs.
Thanks for the reminder.

> What kind of 6' dish? Prime focus or offset?
All offset.

> The problem with using those LNBFs are they were designed for the smaller dish.
I had never considered that the open aperture of the LNBF might not admit the full signal !! That said.. my six foot dish does have ridiculously higher signal on the "point dish" than my 4 foot. (80 versus 50 for spot)

 

[Mr Tony]

> What kind of 6' dish? Prime focus or offset?
All offset.

> The problem with using those LNBFs are they were designed for the smaller dish.
I had never considered that the open aperture of the LNBF might not admit the full signal !! That said.. my six foot dish does have ridiculously higher signal on the "point dish" than my 4 foot. (80 versus 50 for spot)

because its offset the LNB's will work just fine.

 

[MikeInAlaska]

> because its offset the LNB's will work just fine

This because the LNB can be moved further away from the dish until the signal cone is fully admitted?