Specifications

page 26
[
StarServe Installers Guide
]
Broadband Video
Broadband Video refers to multiple video signals transmitted
via a single medium, such as television (terrestrial broadcast),
satellite or cable. Video transmitted over the air (television) is
basically the same as that transmitted over cable or via
satellite. The primary difference between any of the mediums
is the signal level.
To be able to transmit numerous video signals across a single
medium, each video signal must only use a portion of the
available bandwidth.
Bandwidth
Bandwidth refers to the amount of information a given device
or cable can reliably transmit. Bandwidth is indicated by a
frequency range. When only a single figure is stated, the
assumed lowest value is zero. The higher the value or broader
the range, the greater the bandwidth.
A twisted pair system rated at Category 5 or greater has a
potential bandwidth of 100MHz. RG-6 quad shield cable can
have up to, 29GHz (Gigahertz) bandwidth.
It is important to note that correct installation of cabling and
equipment is critical to maintain the maximum bandwidth.
Modulation
For audio and video signals to be transmitted using only a
portion of the available bandwidth, they are modulated onto
carrier signals within a fixed bandwidth. In Australia, the
standard bandwidth is 7MHz, this is known as a channel.
If TVs or VCRs are tuned to a particular channel, it is not
tuned into a single frequency, but a 7MHz band from which
the audio and video information is retrieved.
For analogue transmission in Australia the vision carrier is
1.25MHz above the lower frequency for a given channel’s
bandwidth, with the primary audio approximately 5.5MHz
above that. The secondary audio is approximately 242KHz
above the primary audio.
Australian Channel Allocation
PAL AUS
Channel No. Freq. (MHz) Channel No. Freq (MHz)
28 527.25 48 667.25
29 534.25 49 674.25
30 541.25 50 681.25
31 548.25 51 688.25
32 555.25 52 695.25
33 562.25 53 702.25
34 569.25 54 709.25
35 576.25 55 716.25
36 583.25 56 723.25
37 590.25 57 730.25
38 597.25 58 737.25
39 604.25 59 744.25
40 611.25 60 751.25
41 618.25 61 758.25
42 625.25 62 765.25
43 632.25 63 772.25
44 639.25 64 779.25
45 646.25 65 786.25
46 653.25 66 793.25
47 660.25 67 800.25
Analogue signal