Iceberg,
if you have an LNB, it will be a module that's detachable from the feedhorn. With an LNBF, it's all in one. The feedhorn itself is a cylindrical tube, which creates a resonant cavity for the 4 GHz microwave signals. The actual "antenna" is a small stub monopole, located at the appropriate point inside the resonant cavity. Surrounding the feedhorn are the scalar rings, that control sidelobe influence. The scalar rings usually mount to the support legs, and the feed slides into the rings at the proper focal depth and is clamped with a screw.
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This one might sound stupid, but I always see C-Band higher in the sky than KU. Is there something different with C-band collecting the signal than KU? <
I think this has already been answered, but the main difference is that C-band dishes are "prime focus". I.e., the feed is located right in the center of the dish at the focal point. Primarily, this is because the portion of the dish occluded by the feed is very small with respect to the full dish surface area. C-band dishes point directly at the satellite you're receiving.
With Ku, dishes can be much smaller, and they went with offset dishes, which move the feed off to the bottom, so that the feed doesn't block the dish at all. Ku dishes are actually slices out of a full parabolic dish. Ku dishes point below the satellite you're receiving. The other advantage this provides is that the dish surfac is then more vertical, so a lot less snow tends to build up than with a C-band dish, especially towards the center of the arc, where the elevation is highest.
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How much of a bugger is it to get the Anchorage stations on C-Band? <
It depends on your location (obviously) and the size of the dish. If you're talking about the DVB group on AMC7 (at 137W), I'd say you have a decent chance, since you're farther West than I am, and I was able to pull the analog Denver stations in, back when I had a 7' mesh dish on my balcony. If you mean AMC8, I'm not so sure. I was never able to get that one, back when the Satcom-C bird was located there, but the power is a lot higher now with the replacement birds.
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I'll be setting this on my deck or outside my garage and just testing it to see if it actually works (the person I got it from said it did). I cant pole mount it so I'll just build the dish and put the LNB on and ghetto move it <
A polar mount would make things a whole lot easier, especially if you plan on ever viewing more than one bird. Even an az/el mount would be handy. If you're planning on just a "prop and aim" configuration (i.e., like one of the old "patio mounts"), I think you'll want to pick a bird and leave it there. Kind of a shame not to take advantage of everything that's available on C-band though.
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Sorry if these sound dumb..I know a loot about KU, <
That's true. You've been a "cash" of information on the subject.
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but C band is really new to me <
Not a problem. I'm sure lots of folks will be happy to chip in with info.
drhydro warned:
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remember that if you dont hook up the polarity selenoid on the feed horn to a reciever you will only get the polarity that the selenoid was previously set at. <
This is true if you have a polarotor on your feedhorn (and separate LNB). But depending on your feed configuration, you might have dual-porting (two fixed LNBs), or if it's an LNBF you could have dual V/H outputs, or the standard 13/18V polarity control that you're used to with Ku.
- Tim
