Two C-Band LNBF's

[PopcornNMore]

Approx. how many degrees apart are two C-Band LNBF's together side by side with the scaler ring attached?

I currently have a C-band LNBF on a stationary 8' dish aimed at AMC3 (87 degrees) and attached a second C-band LNBF directly onto one side in hope of receiving any satellite 87 degrees or higher. No matter how much I adjusted I received no signal from the second LNBF.

 

[PopcornNMore]

After reading several threads on mounting multiple LNBF's I believe I have it now. Someone pointed out that 1 degree equals approx. 1.5" apart for the LNBF's.

 

[Mr Tony]

I dont know how it is on the 8 footer but on the 6 footer if the LNB's touch its 4 degrees. If the scaler rings are on and the scaler rings touch its 8 degrees
The 4 degrees you have to cut the scaler rings

http://www.satelliteguys.us/c-band-satellite-discussion/147673-2-c-band-lnbs-6-foot.html
http://www.satelliteguys.us/c-band-satellite-discussion/92274-2-c-band-lnbs-one-6-a.html

 

[SatelliteAV]

The distance between the LNBFs to receive multiple satellites will vary from dish to dish and your location.

The distance is dependent on the dish F/D and the look angle to the satellites based on the install location's Longitude and Latitude in relationship to the orbital slots..

 

[FaT Air]

So, in other words, if set up for 6 degree separation directly overhead(close to due south) it won't be 6 degree separation if you move the dish towards either horizon? I've never done it, (Set up 2 feeds on a dish) but have contemplated, so I have to ask.

 

[Anole]

Iceberg, ACradio, and Pendragon come to mind immediately as having mounted two C-band feeds on a BUD.
If you can get the search engine to look for an appropriate key word on threads they're in (or started), you can get a lot of great advice.

If you'd like an actual numerical answer for two birds in question, this thread should help:
MJflash and his math to put two LNBs on a single dish:
http://www.satelliteguys.us/free-air-fta-discussion/89049-offset-lnbs-theory-practice.html
I know I've run through the numbers many times (once to encourage Linuxman on multiple Ku LNBFs on a 6' offset Prodelin)

This was also kind of a fun read:
Mike Kohl does Skyvision wide-swath dish:
http://www.satelliteguys.us/free-air-fta-discussion/181923-whats-new-skyvision.html

But like lots of things sat-related, once you've got a feel for it, you can do it without a safety net.

 

[FaT Air]

Looking over the posts provided, it confirms my thoughts. Thanks. Now I know I can't put two feeds on a moving dish, and have them be looking at sats X degrees apart, throughout the arc. Darn, there's one spring project in the can. Oh well, got two more, 'n one's going to be fixed. The wheels are turnin'.

 

[SatelliteAV]

The spacing will be acceptable for most C-band signals until you near the ends of the arc. Never thought about placing multiple C-band feed horns on a motorized dish. I have one offset LNBF on my KU band that switch on only for 103W unique skew.

What was your plan for the offset feed horn? Circular / linear?

 

[Anole]

Looking over the posts provided, it confirms my thoughts. Thanks. Now I know I can't put two feeds on a moving dish, and have them be looking at sats X degrees apart, throughout the arc.

. . . wait now . . . why would you want to?

On another note, please read through this thread for encouragement:
C-band Linear/Circular Orthomode Feed

 

[PopcornNMore]

I dont know how it is on the 8 footer but on the 6 footer if the LNB's touch its 4 degrees. If the scaler rings are on and the scaler rings touch its 8 degrees
The 4 degrees you have to cut the scaler rings

http://www.satelliteguys.us/c-band-satellite-discussion/147673-2-c-band-lnbs-6-foot.html
http://www.satelliteguys.us/c-band-satellite-discussion/92274-2-c-band-lnbs-one-6-a.html

I was thinking that it would be about 8 degrees and that I should be receiving Galaxy C3.

 

[PopcornNMore]

Things that make you go hmmm...

Because I was receiving no signal from the second C-band LNBF this morning I did the following:

1. Since I never used the second coax line I swapped the connections to verify proper communications. The second coax line tested to be good as expected.
2. I then tried adjusting the second C-band LNBF once again on the left hand side looking to receive any satellite. No signal!
3. Just for fun I placed the second C-band LNBF on the right hand side as pictured below. I'm now receiving Galaxy 17 at 91 degrees with a signal strength 70+ on most channels.

Unknown Questions:
1) How can I be receiving Galaxy 17 with the second LNBF positioned on the right hand side of the first (centered) LNBF? I thought I would find something like AMC9.
2) How can I be receiving Galaxy 17 having both scaler rings on with only a 4 degree separation? I would think this should be more like 8 degrees.

 

[Anole]

Unknown Questions:
1) How can I be receiving Galaxy 17 with the second LNBF positioned on the right hand side of the first (centered) LNBF? I thought I would find something like AMC9.

This is proper. Think about the dish acting as a mirror.
Your LNBF is off-center, so where it looks (reflecting off the dish) is off-center to the other side.

2) How can I be receiving Galaxy 17 having both scaler rings on with only a 4 degree separation? I would think this should be more like 8 degrees.

As Iceberg, Brian, and I mentioned above, you have a different size dish (and different focal length), so your results are different.

edit:
Nice pix. Quick 'n easy mount-job, there!

 

[PopcornNMore]

This is proper. Think about the dish acting as a mirror.
Your LNBF is off-center, so where it looks (reflecting off the dish) is off-center to the other side.

As Iceberg, Brian, and I mentioned above, you have a different size dish (and different focal length), so your results are different.

edit:
Nice pix. Quick 'n easy mount-job, there!

However, when motorized Galaxy 17 is on the other side since I live on the East. Even when stationary if I wanted the center feed to see Galaxy 17 I would need to turn the dish to the left. I know, because I did this hundreds of times. My head is spinning.

I'm also receiving the networks from Galaxy 3C at 95 degrees on the same second feed. However, I saw that the polarity is reversed. For example EWTN is V not H. When I adjusted the feed I lost all of Galaxy 17 and only received Galaxy 3C. I'll keep on experimenting.

 

[PopcornNMore]

Now the secondary LNBF is properly adjusted and I'm receiving only Galaxy 3C which is exactly 8 degrees away from AMC3. Quality on both LNBF's is excellent. The only problem is that now I only receive 4 networks (2 Spanish) and horse racing.

I'm looking for a longer screw that would enable me to position the secondary feed below the primary feed which would move it in enough to receive Galaxy 17 without cutting the scaler ring.

 

[PopcornNMore]

I found longer screws and attached the secondary LNBF under the primary LNBF using the holes within the scaler rings, but for some reason they just couldn't tighten enough to hold the secondary LNBF in place. Plus I don't know how this would have affected reception of AMC 3.

Receiving both AMC 3 and Galaxy 17 would be ideal. I'll keep trying.

 

[catamount]

Read Anole's post once again. He is completely correct. Your second lnb will either be on 91,93,95 etc. according to dish size and adjustment.

Here is a pic of my mini-bud; same principle. I'm on East coast

Looking from behind dish from left to right: 101ku, 91 Cband, 83 ku

 

[PopcornNMore]

Question:
Currently I have two runs of coax from the 8' dish going into the communications room within our basement. My other dishes also have coax runs that also go into the communications room into a diseqc switch which is attached to the OpenBox S9 receiver. What would I need in order to add additional LNBF's onto the 8' dish?

I'm thinking I would need to use a 22KHz switch to swich between the second and third LNBF. Then my setup would be something like this:
diseqc port 1: Primary C band LNBF
diseqc port 2 - 22KHz on - Second C band LNBF
diseqc port 3 - 22KHz off - Third C band LNBF

 

[PopcornNMore]

This is proper. Think about the dish acting as a mirror.
Your LNBF is off-center, so where it looks (reflecting off the dish) is off-center to the other side.

I have been tinkering with satellite dishes since 1982 and I never knew this. This just blows my mind.

For example: Facing the dish if I manually adjusted the azimuth to receive Galaxy 16 using the primary centered feed I would move the dish away from AMC 3 turning the dish to the left. However, if I kept the primary feed on AMC 3 and wanted to install a second feed to receive Galaxy 16 I would need to place it on the right hand side?

 

[PopcornNMore]

Found another thread on this topic:
http://www.satelliteguys.us/c-band-satellite-discussion/233198-adding-2nd-lnb-10ft-dish.html

 

[Anole]

Well, I gave ya plenty of reading material.
The side thing should have been covered in at least one of 'em.
I'm positive Pendragon made such a comment in his circular/linear LNBF thread.
I think you'll have an "ah-ha" moment pretty soon, and this'll all be clear. -

As for the switching, there's not really enough info to say what would be best.
I recommend the Switches Simplified FAQ (naturally) and maybe post #6 with eight LNBs as something to try.

Lastly, regarding the swapped polarity of your add-on LNBF, it looks like it's rotated 90° in the pictures, so... V & H should be swapped.