Setting up two LNBs on one dish
Paperhouse
Posts: 1,710 Forum Member
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I completed a task yesterday which I had been putting off because I thought that it was going to be more difficult that it actually was. The job was to install two LNBs on an 80cm dish, so I might receive both Astra 1 and Hotbird.
With the dish erected, the two LNBs were placed (almost touching each other) in a twin holder symmetrically centre to the feed arm. I have previously used an App on my phone to set up a dish, but have never used it for a multi feed situation. I decided to align the dish as if I were searching for Eutelsat at 16 degrees. 16 degrees being about halfway between Astra 1 and Hotbird. I finally set the dish elevation to about 30 degrees. I did nothing more before switching on the receiver.
To my surprise both Astra 1 and Hotbird could be received, each with a signal quality of about 60%. After a couple of minutes trying the LNBs at various positions on the twin holder, almost full signal quality was achieved on both.
It was as simple as that and the job was completed in no time. The App I use can be found at www.exultation.de
With the dish erected, the two LNBs were placed (almost touching each other) in a twin holder symmetrically centre to the feed arm. I have previously used an App on my phone to set up a dish, but have never used it for a multi feed situation. I decided to align the dish as if I were searching for Eutelsat at 16 degrees. 16 degrees being about halfway between Astra 1 and Hotbird. I finally set the dish elevation to about 30 degrees. I did nothing more before switching on the receiver.
To my surprise both Astra 1 and Hotbird could be received, each with a signal quality of about 60%. After a couple of minutes trying the LNBs at various positions on the twin holder, almost full signal quality was achieved on both.
It was as simple as that and the job was completed in no time. The App I use can be found at www.exultation.de
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For reasons that I won't go in to here, when I parked my SNG van the night before a transmission, I had a clear view of the satellite I was expecting to use for the job the next morning.
When I returned to the van early the next morning, I was told that there had been a last minute change of satellite - to 16 East! Unfortunately, very close to the van was a tree right in the direction of 16E. To make matters worse, the van had now been wedged in by other vehicles, (it was very early in the morning, no one around to move them), - so I was well and truly stuck.
As per the OP, I moved the dish either side of the tree, and was able to just "see" 13E and 19.2E each side on the spectrum analyser - not enough to lock a receiver on to. A bit of maths, though in my case azimuth, elevation and polarisation offset, and I pointed the dish to where I though that 16 East should be.
More in hope than expectation, I switched on the two High Power Amplifiers, called the satellite's Control Centre, and sent the full phase combined output of 800 watts into the adjacent tree, (normally less than 20 watts on that transponder ISTR). Amazingly they could see my signal above the noise floor, so I called the client's Control Room and explained the situation regarding the tree. They said that they could decode my signal, though the error ratio was awful - but the pictures looked stable, (this was for news feeds).
It ran for the rest of the day like that, though I kept an eye on the tree