Wavetek 147 Spécifications télécharger pdf (Page 392)

Glossary

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Level Level is a measurement of signal and reference voltages in the cable

system, expressed in dBmV or as a ratio expressed in dB

LPF Low Pass Filter

Modem Modem” is a contraction of Modulator-Demodulator. A Modem

converts computer digital signals to analogue for data transmission, or

demodulates upon receipt, for use within a computer.

Modulate To regulate, or adjust, and specifically in the case of

communications, to regulate some parameter of a high-frequency carrier

wave by means of a low-frequency information signal. (Roddy/Coolen)

NCTA National Cable Television Association: the trade association for the U.

S. cable television industry. Formerly called National Community Television

Association.

Node A point of connection and distribution downstream from the hub. A

node supports an average of about 500 subscribers

Noise Offset For a true indication of Mean Noise value in the system,

measure C/N ratio at about 2.4/2.5 MHz above the lower band edge,

between video and chrominance modulation.

Overlapping Channel Many countries have similar but slightly different

frequency allocation for channels.To accommodate all possible variations,

Stealth base channel plans have some overlapping frequencies. Carrier

frequencies are different, but there is some bandwidth overlap. if you use

one of these channel plans, delete unused channels that overlap active

channels.

NTSC National Television System Committee: the organization that

established a color television standard with the same name used by the US

and several other countries. The standard uses a 525-line screen at a rate of

sixty fields/thirty frames per second, with a broadcast bandwidth of 4 MHz.

Horizontal resolution is approximately 768 pixels.

PAL Phase Alternate Line: a European color television system, not

compatible with the NTSC system used in the United States

PAM Pulse Amplitude Modulation produces a sequence of possibly

overlapped pulses with the amplitude of each modulated by a symbol. QAM,

PSK, BPSK, PRK, QPSK, DPSK, and AM-PM are all special cases of

passband PAM

Pass band The range of frequencies accommodated by a given filter,

amplifier, or circuit.

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Wavetek 147 Spécifications Page 392