Assuming BW employs accepted frequency management techniques, measures will have been taken to minimize/prevent mutual interference between or among the 2 TX and 2 RX frequencies. Given frequencies that were determined to be non-interfering, you could technically park the dishes side-by-side. However, NIB frequencies are assigned assuming all hardware is functioning properly. Equipment that leaks RF throws even the best frequency management efforts out the window. Without expensive monitoring equipment, the best thing you can do is space the dishes based upon diameter. Interference is tricky, so I'll tell you up front that there are no guarantees. But if low powered dishes are >3 diameters apart - harmonics and even leaking signals often become too weak to be troublesome. Ask your Signal Corps guys about spacing their mobile rigs. I expect you'll hear something similar.
« Last Edit: Mar 1st, 2010 at 3:27pm by USN - Retired »
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Eric Johnston
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Reply #1 - Mar 1st, 2010 at 4:18pm
If you have two HX modems you need two transmit BUCs, each with its own antenna. This is because a (Hughes) BUC is designed to work with a Hughes modem and transmit only one transmit carrier burst at any instant.
If you have two modems you have the possibility to transmit two bursts simultaneously and thus twice the total transmit traffic bit rate. Having two modems, feeding BUCs on separate dishes, makes this possible. *
As far as spacing is concerned the dish in front must not block the beam from the one behind. If the dishes are side by side and facing straight ahead, leave at least enough room so you can walk between them and work on one without interfering or blocking the beam from the other. A wider spacing will give flexibility for the future e.g. such as working to different satellite, so close spacing should be avoided if you are mounting in non-moveable concrete.
I would suggest that you do not bind the two pairs of cables together, but route the pairs seperately, along with any heavy duty earth cables between the antenna bases and the indoor AC mains outlet point. Avoid the possibility of LNB or BUC DC supply currents returning via the cables going to the other antenna. A unknown open circuit in the sheath of one of the BUC cables could give you some weird symptoms and diagnostic problem.
Best regards, Eric.
* If anyone wonders how this might happen without the bursts colliding at the satellite, note that the HX hub has multiple return-link burst receivers and the hub will assign return link frequencies in real time so that simultaneous bursts from remote sites are on different, but nearby, frequencies according to what hub receivers are available at that moment.
