מושגים מעולם הלווינים (כל מה שרציתם לשאול ולא העזתם)

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הצטרף: 23 דצמבר 2003, 09:33
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מושגים מעולם הלווינים (כל מה שרציתם לשאול ולא העזתם)

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Terms and FAQ



Actuator

The motor arm that moves the dish on a polar mount from side to side. The motor usually runs on 36 volts DC.



Az/El mount

A manual satellite dish mount, where you have to adjust the elevation and azimuth manually independent of each other (up/down and sideways).



C-band

3700 to 4200 MHz frequency band (3.7 to 4.2 GHz)



DVB

Digital Video Broadcast, an international MPEG2 encoding and transmission standard. This system is not compatible with DCII transmission.



FEC

Forward Error Correction, a way of transmitting the same data twice in case some of the data was lost the first time. This is useful under weak signal conditions.



Feed horn

A circular opening located at the focus point of the dish. Radio waves enter the opening and is guided down the feed horn. The radio waves will be picked up by an LNB or LNA connected to the feed horn.



Footprint

The coverage area of a satellite transmission. It defines a region on the surface of the earth where the signal is receivable. A satellite can have several beams (footprints) with many different coverage areas.



Frequency

The number of waves per second in a radio wave.

kHz - 1000 waves per second

MHz - 1000000 waves per second

GHz - 1000000000 waves per second



Gain

Power of amplification, or amount of amplification, often measured in dB. Negative gain is loss of signal.



Geostationary

An orbit around the equator of the earth where objects (satellites) seems to be standing still in relationship with a fixed point on earth. The satellites seems to be standing still in the s**. They are of course moving at the same rate as earth's rotation, one revolution per 24 hours.



H-to-H mount

A special satellite dish mount that will track satellites down to the horizon, both in the east and west. The dish has a travel range of 180 degrees.



Ku-band

11.700 to 12.200 GHz (US)

10.600 to 12.900 GHz (Europe)

12.200 to 12.700 GHz (DBS)



LNB

Low Noise Block down converter, a device that amplifies and converts a block of frequencies to a lower block of frequencies. The LNB is an active device placed at the focus point of the dish.



LO

Local Oscillator, a circuit in the LNB(F) or LNC. It determines how much the frequency is downconvertet by in the LNB(F) or LNC. Standard LO for C-band is 5150 MHz, and 10.750 GHz for Ku-band.



MPEG

Motion Pictures Expert Group, a digital compression standard for audio and video.



Noise Figure

The amount of noise a device is generation on its own. Lower noise is better, and is often a measurement of the quality of a LNB, LNA or LNBF.



Offset dish

A dish where the focal point is not in the center of the dish. This is common on Ku dishes, and the offset angle is often 30 degrees. The reason for using the offset dish is that the LNB and feed is not creating a shadow on the dish, thereby giving higher efficient of the dish. When the dish edge is vertically, seen from the side of the dish, it is actually looking at an angle of 30 degrees upwards.



PID

Packet IDentification, a header in a packet of data telling what the data is for.



Polarity

Radio waves are polarized. They can be linear or circular. Linear polarity is Vertical or Horizontal, circular polarity is Righ-hand and Left-hand circular polarity.



Polarizer

A device that selects the received polarization of the radio waves. It can be a small motor turning the pickup probe, or done electronically in an LNBF.



Polarmount

A special satellite dish mount that setup correctly will track all the satellites in a geostationary arc in the s**, from east to west. Only movement sideways is necessary, the up/down adjustment is done by the polarmount itself.



Reed Sensor

Used in actuators and dish motors to report back the movements of the dish. A counter in the motor control unit can tell where the dish is pointing, and the information can be stored and retrieved when you want to move the dish to a specific satellite. Only two wires are required to connect the sensor.



Scrambling

A way of distorting the picture or sound so it is not viewable. A descrambler is needed to receive the correct signal. This is used to transmit audio and video securely, or to get payment for the service.



SR

Symbol Rate, the amount of data transmitted every second.



Transponder

A satellite channel with an assigned frequency and polarity.



14/18 volt switch

A change in the voltage on the LNB coax cable. This change of voltage can control the polarity in a LNBF, or switch other devices on the coax cable.



22kHz switch

A tone that can be sent via the LNB coax. This tone can control the LNB or switches on the coax cable.



DiSEqC

digital satellite Equipment Control.



MPEG

Moving pictures Expert Group.



C/N

Carrier to Noice-ratio.



NTSC

National Television Standards Committe.



SECAM

SEquential Couleur A Memorie.



PAL

Phase Alternating Lines. :D :D :D
my collection so far :
dreambox7020|UCAS programmer| analog signal meter|manhattan |matrix reloaded|
1.80 + 1.2 + 1.60 dish|1.80 + "24 actuator
סמל אישי של משתמש
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הודעות: 792
הצטרף: 23 דצמבר 2003, 09:33
מיקום: חיפה

אכן זה התיכנון:

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אם היית קורא גם הודעות אחרות כאן ,

היית רואה שהתיכנון שלי זה לתרגם לעיברית את הדברים העיקריים ,



אבל זה דורש הרבה זמן ,



ולכן בנתיים אני מעלה לטובת הכלל את המאמרים באנגלית,

חלק מהאנשים כן קוראים ומתעניינים - אפשר לראות לפי התגובות.



בכל מקרה , תודה על ההערה ,

אמיר.
my collection so far :
dreambox7020|UCAS programmer| analog signal meter|manhattan |matrix reloaded|
1.80 + 1.2 + 1.60 dish|1.80 + "24 actuator
סמל אישי של משתמש
איציק
אחלה חבר
אחלה חבר
הודעות: 368
הצטרף: 28 דצמבר 2003, 00:36
מיקום: ראשון לציון

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