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waterlock devices which provide an effective way to keep moisure away from

the LNB’s F connector.

The receiver should be unplugged from the a.c. wall receptacle before

connecting or disconnecting the coax cable from the LNB or the receiver. This

eliminates the chance of a short circuit across the coaxial connections.

The connection to the LNB also should be weatherproofed to keep moisture

out. This can be done by flooding the connector with a dielectric silicone sealer

or wrapping the connection with a sticky waterproof compound such as Coax-

Seal. It is also a good idea to use a plastic LNB/feedhorn cover to give your

outdoor electronic components added protection from the elements.

Wiring The Feedhorn

The feedhorn line of the direct burial cable is comprised of three color-coded

22 gauge (or larger) stranded wires. These wires also are shielded and

jacketed. The three wires provide power, pulse, and ground connections for

the feedhorn. Each of these wires connects to corresponding terminals on the

back of the receiver. The wires are color-coded to help identify them when

connecting to the three servo motor wires at the feed (usually red for power,

white for pulse, and black for ground).

A stranded wire is used because it is more flexible and won’t break as easily as

a solid wire. The shield, an aluminum foil wrapped around all three wires,

keeps impulse noises from entering the line and giving false pulses to the

receiver. The receiver uses pulse to keep track of the position of the feedhorn’s

pick-up probe. You therefore can adjust, or “skew”, the position of the probe

and program the optimum polarization for any given satellite transponder into

memory.

The feedhorn’s servo motor rotates the pick-up probe, which swings back and

forth while switching between the horizontally and vertically polarized

transponders (odd and even channels). Keep in mind that there are limits to

the pick-up probe’s clockwise and counter-clockwise movements. The

feedhorn must be aligned on the antenna a that the probe can swing the 90

degrees from horizontal to vertial (or left-hand to right-hand circular)

polarization without reaching the limits of its travel. Several manufacturers

include a directional guide with their feedhorns to show the proper alignment of

the feed when installed on the dish. If you find that you cannot skew the probe

beyond a good picture on both the odd and even channels on all satellites, you

will need to loosen he clamp that holds the feed onto its support and physically

rotate the feedhorn until it is possible to do so.

Summary of Contents for Large Dish

Page 1: ...off and the dish flung through the sky Because roof top installations are more susceptible to microwave interference than those on the ground a site survey with a spectrum analyzer or an on site rooftop demonstration with a small potable dish is an absolute necessity in any country where microwave interference is a major potential problem If several of your neighbors have antennas you can check wi...

Page 2: ...hich is curved so that it resembles a hook allows the feed to be mounted looking back at the center of the dish Guy wire kits are available for button hook supports that will provide the additional stability required for reception of both C and Ku band signals Ku band signals are much higher in frequency and there fore are beamed Earthward in much smaller wave lengths Consequently the antenna curv...

Page 3: ...ntenna s rim so that it crosses in the center of the dish The depth will be the distance from the antenna s center to the string Many feeds today have adjustable scalar rings These feeds can be broken down into two parts a round flat scalar plate with concentric circles on its surface and the wave guide onto which the LNB is mounted This wave guide fits into the center of the scalar plate and can ...

Page 4: ...iewing TV signals and watching the receiver s signal level indicator If you are going to have a technician during the final stages of the installation he will have a portable meter to use at the dish Two people also can talk back and forth via walkie talkie or portable phone while one makes adjustments to the dish and the other keeps an eye on the quality of the reception Direct burial satellite c...

Page 5: ...c impedance rating of 50 ohms and is not suitable for satellite TV use Be sure that the cable you buy is 75 ohm coax There are several different kinds of 75 ohm coaxial cable available RG 59U coax can be used to span distances of up to 100 feet For longer lengths lower loss RG 6 or RG 11 are used Direct burial satellite cable contains one or two spans of RG 6 Since RG 6 is slightly larger in diame...

Page 6: ...e and black for ground A stranded wire is used because it is more flexible and won t break as easily as a solid wire The shield an aluminum foil wrapped around all three wires keeps impulse noises from entering the line and giving false pulses to the receiver The receiver uses pulse to keep track of the position of the feedhorn s pick up probe You therefore can adjust or skew the position of the p...

Page 7: ...minals Some satellite receivers have an external power supply that puts the large transformer outside of the receiver chassis This reduces the receiver s size as well as its operating temperature The power supply is actually a large transformer that turns 110 or 220 volts a c into 24 to 36 volts d c to power the actuator s d c motor Grounding The System If your home s a c electrical ground is clos...

Page 8: ...omewhere in the middle of the continent observe how they are mounted on existing systems in your area or ask your satellite retailer which is the correct method for you Dish Alignment Settings You have now completed the basic construction of the dish and are eagerly anticipating your first pictures from space To fine tune those pictures and get your dish to track you or someone you can communicate...

Page 9: ...ast satellite to the east and west Setting the polar axis elevation of the dish Extend the drive until the dish is looking at the highest point in the sky Set the inclinometer onto the polar axis of the mount to the correct elevation angle for your location Setting the declination Declination is the offset angle between the polar axis of the mount and the rim of the dish which permits the antenna ...

Page 10: ...en as you move the dish past a satellite You can go back to where the flashed occurred turn off the scan feature and identify the satellite by comparing the programming you encounter to the satellite TV program grids Some satellites only carry a few active transponders Without the scan feature you would need to select an active transponder and tune to the correct polarization before you could find...

Page 11: ...just viewing the picture on the TV screen 4 For locating satellite in the lower section of the Clarke Orbit push the dish right and left on the pole and move the drive east and west in slight increments until you are satisfied you have the strongest signal Then tighten the mount s bolt onto the pole so that the dish won t rotate Do not tighten them down firmly yet however Note the numerical readin...

Page 12: ...tomatically appear on their respective channels on the TV If your satellite receiver does not have this feature you will need to purchase an A B switch from your local satellite or electronics store Both the satellite receiver and local antenna connect to the A and B input ports on this switch while the single output port connects to the antenna input on the TV This switch will have to be changed ...

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