Hi, I am from Pakistan.I can't receive c band channels on my satellite dish from last 8 months.After a search i come to know that there is Local Wireless (WIMAX) interruption in the signals .Please help me by advising what i have to do to receive c band channels again as all Pakistani channels are on C band.Please help.
snipped-for-privacy@gmail.com hath wroth:
Please read this page before beginning:
Note that WiMax interference is possibly the result of your government allocating BWA (broadband wireless access) service in parts the satellite band (3.4 to 3.7GHz). They claim that interference would not be a problem because Wimax operation travels parallel to the ground, while your C-band dish is pointed upward. That will work, but only if your dish does not "leak" or have holes that pickup signals from directions other than the satellite. If you dish is made from mesh and is bolted together, be sure to check if there are any gaps or loose screws.
Next, you need to determine where the WiMax base station tower is located. Then construct an obstruction between your dish and the tower. This explains how it's done:
Next, you might need additional filtering in front of your LNB:
This goes between the polarization switch and the LNB. If the WiMax service is operating in the C-band, this will probably do little.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
The added dish skirt has a somewhat different purpose. It was to eliminated direct pickup to the dish feed. Most C-Band dishes are rather deep (small f/D ratio) causing the feed to be buried below the edge of the dish. While the dish edges don't get much illumination, there's also very little pickup from the sides. The dish shields the feed horn.
However, a larger F/D ratio dish results in a more shallow dish, which in turn results in the feed being located well above the edge of dish. No shielding by the dish here. For optimium gain with a Chaparral type feed, there will always be a small amount of overspray or spillover.
That shows up as unwanted pickup at the edges of the dish. In order to block that direct pickup, a skirt is added. The skirt is somewhat effective with a deep dish, but next to useless with a more shallow dish.
Therefore, if the WiMax interference is coming from a direction that is in line with the feed to the edge of the dish, a skirt will help. If it's the usual problem of gaps in the mesh reflector caused by lousy construction or assembly, it won't do much.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
Thanks to all members I have now solid dish of 8 feet,before that i had mesh dish which i replaced because of this problem but all in vain.Any how,i don't know the shape of wimax tower but all mobile and different towers are on right side of my dish and these are about 200m from my dish.I am receiving all ku band channels easily but only problem is in c band.
snipped-for-privacy@gmail.com hath wroth:
The WiMax system operates near or in the C-band. Ku band should be unaffected. Only C-band will be a problem.
200m is very close, especially if the towers are line of sight. Can you see the towers from the dish? Can you move the dish?Since you know the probable location of the WiMax tower, you should be able to place an obstruction between your dish and the towers. Anything that will absorb RF will work. Try aluminum foil, chicken wire, wire mesh, sheet metal, or a wet blanket. Start by setting up a temporary barrier between the LNB feed point and the probable sources of interference. A small piece of aluminum foil on a wooden stick will work for testing. Move it around the LNB to see which location works best. If it goes away completely, then that's the direction the interfrence is coming from.
If that is insufficient, try blocking the signal using a very large piece of chicken wire or mesh that is larger than the dish diameter. You're building an RF wall. This is not permanent and is only to see if the interference can be blocked. If it's coming from multiple directions, this is going to be difficult. Use this as a guide:
It may also be possible to move your dish to a location that does not look directly at the WiMax towers. If possible, locate the dish so that a building or other large object is between your dish and the cell towers.
If your dish is on a roof top, please consider moving the dish to ground level to avoid terrestrial interference. Nearby buildings will provide the necessary obstructions while hopefully, not blocking your view of the sky.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
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