Planet Fox > Microwaves > Satellite TV Primer

Satellite TV Primer

Remember BUDs? Those were great. So great I have three of them! Maybe you've got an old BUD, or Primestar dish, or Super Dish and you're wondering if there's anything you can do with it. The analog receivers originally used with BUDs are (nearly) worthless today, Primestar receivers are worthless, and Dish Network no longer uses the 105° FSS orbital location, but what about the antennas themselves, is there anything you can still do with those? Fortunately, there is.

Types of Antennas and Bands

First you have to know what kind of dish you have. There are two common bands used for satellite broadcasting, C-band from 3.7-4.2 GHz and Ku-band from 11.7-12.2 GHz. C-band antennas, coloquially referred to as BUD, big-ugly-dishes, etc... are usually 2M in diameter or larger. Most common C-band dishes are prime focus antennas, with a reflector made from fiberglass or aluminum mesh. Motorized dishes were used to receive programming from more than one satellite by using an linear electric jack powered by the receiver to physically move the dish. Such dishes are mounted on a polar mount, which is aligned exactly with the earth's poles. C-band antennas made from 1988 onwards are usually also capable of receiving Ku band if fitted with the proper type of feed.

Ku band antennas are usually relatively small - 1M diameter antennas are common, but they can be larger. These are made of fiberglass for higher end models or pressed steel for the cheaper ones. Ku band antennas are usually offset prime focus antennas, which are more efficient for smaller diameter reflectors because the feedhorn and LNB aren't in the signal path. The smallest size generally considered acceptable is 75cm for a round dish. Primestar and Super Dish antennas are both examples of excellent Ku band antennas; for advice on adapting those for other purposes, see my articles on the subject.

Uses for Old Receivers

So, if you can't use the old receivers, what can you use? Well, I never said all of the old receivers were useless. The subscription channels may be gone, but the old analog and Digicipher receivers are still useful for bringing in feeds - news staions, radio stations and others send each other video and audio over both C and Ku band in these formats. Sometimes it takes a while to find them, though, since by definition a feed isn't broadcasting all the time.

New Receivers

The most common type of new receiver is the DVB receiver. DVB is an international standard for digital video broadcasting used extensively all over the world for satellite broadcasting, and most of the world (ex; everywhere but the US)  for terrestrial and cable transmission. DVB-S uses MPEG II video encoding, MPEG I layer 2 audio coding, and QPSK (2 bits per symbol) modulation. The newer DVB-S2 specification uses MPEG IV video and audio coding and (usually) 8PSK (3 bits ber symbol) modulation.

New DVB receivers cost between $60 or so for basic models all the way up to about $300 for super fancy models with all the fruit. DVRs, HD, SD, stuff with integrated terrestrial tuners, internet streaming, wifi, are all great features you can get with these receivers. The best part is that they work with pretty much all existing C and Ku band equipment.


DVB programs can be unencrypted "free-to-air", or encrypted with one of a variety of encryption algorithms: Nagravision (used with Dish Network), Cryptoworks, Iredto, Betacrypt, and Conax CAS. The best encryption for DVB streams is BISS, which is a free, open, standardized system not owned by any particular company. The worst is PowerVu, which is proprietary, obscenely expensive, and the exclusive property of Scientific Atlanta, which doesn't technically exist anymore.

Because everyone involved with the US pay-TV industry is retarded and evil PowerVu is the dominant form of encryption used here. As far as I know, there aren't any IRDs meant for consumer use that use PowerVu, although you could buy a commercial receiver like the D9223, but I don't think there's any way to get it authorized right now. For this reason I and many others are actively lobbying for the retirement of the ugly mess that is PowerVu for good in favor of anything else.

The better DVB receivers have a PCMCIA slot, called a DVB Common Interface that allows the receiver to accept a CAM (conditional access module) to be used for whatever encryption system you need. These aren't much use in US yet (see; retarded, evil) but are used extensively around the world for pay-TV service.


Adapting "polarotor" type feedhorns for use with modern receivers

Unfortunately, most new receivers don't have provisions for dealing with the 5V servo motors used on older C-band feedhorns for switching between polarities - which means as is you'll only be getting half of the transponders available on any particular satellite. There are a number of ways around this. The easiest is probably to replace your old feed with a 13/18V switched dual polarity C-band LNBF like the DMS International BSC-421. The highest performance option requires two LNBs: get an ortho-mode-transducer or dual feed which has two LNB ports, one for each polarization and combine them with a regular old multiswitch. A third, and possibly the coolest option is to track down an automatic polarizer, which takes the 13/18V your receiver uses to select polarity and moves the servo motor accordingly.

Adapting positioner motors to modern receivers

Modern receivers can't power the older motorized dishes on their own, but you can get a little device like the V-box which takes the digital commands issued by your receiver and moves the actuator on your dish accordingly. Most receivers will let you program in the position of dozens of satellites, and will move the dish to the right satellite automatically when you change channels.

Combining multiple dishes onto one cable

There are a two different options for remotely switching between different antennas. A 22kHz "tone burst" switch has two inputs and one output: the output is connected to one input normally and switches to the other input when your receiver sends a 22kHz tone down the line. If you have more than two different feeds, you can use a DiSEqC switch, which can have up to 16 inputs.

Receiving multiple satellites with a single dish

If you don't have a motor, but you'd still like to receive programming from more than one satellite you can get a multi LNB bracket. These wild looking assortments of clamps, brackets and tubes allow you to mount extra LNBFs over your dish's reflector in various positions. This is a good option for two to five satellites that are all within 20° or so of each other, but impractical for larger setups.

Keep in mind that your antenna's reflector is a mirror, so the position of the LNBFs will be backwards from their position in the sky. For example, the lowest satellite on the left will be picked up by the highest LNBF on the right side of the dish. The larger the dish, the greater the spacing between the LNBFs will be.

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