Wavetek 147 Especificações descarregar pdf (Página 360)

Application Notes: Proofing and Testing

336

The video level for each channel at the end of a 100 foot drop will have:

• > 3 dBmV [76.605(a)(3)].

• < 8 dB variation over 24 hours & 6 months [76.605(a)(4)].

• < 3 dB of variation between adjacent channels [76.605(a)(4)].

• < 12 dB of difference between any 2 channels in a 500 MHz system and

1 dB allotted for each 100 MHz above 500 MHz. This is tilt and peak-to-

valley [76.605(a)(4)].

• A maximum level is stated that doesn’t overload the subscriber’s

receiver [76.605(a)(4)].

• The audio will always be lower than the associated video. The audio to

video delta shall be between 10 and 17 dB. One exception to this rule is

if a baseband converter is used, then the delta is specified for 6.5 to 17

dB [76.605(a)(5)].

In-Channel Sweeping [76.605(a)(6)]

If you want to perform an In-Channel Response (ICR) test, there are two

scenarios to choose from:

1. Use your existing sweep transmitter or

2. Obtain a function generator that will sweep, at a line rate (approx.

20ms to 50ms), from 250 kHz to 6 MHz.

Adjust the output level to meet the requirements of the modulator's video

input (~ 1 Vp-p).

NOTE: As of 12-30-99, In-Channel Response testing must

be done after the customer premise equipment, which

means after the setup box. The FCC rule is ± 2 dB of

flatness.

You must create a new channel plan for each channel that you will be doing

the test on. This is done on the Transmitter (Tx) or on the field unit if using a

function generator.

When building this channel plan, create ten (10) scrambled channels, 500

kHz apart, starting approximately .75 MHz above the lower boundary of the

cable channel continuing 5 MHz above.

After you have created the channel plan, select the appropriate mode from

the SWEEP RECEIVER menu. Select the Stealth mode if using the Tx or the

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Wavetek 147 Especificações Página 360