Motorola BT100 operation manual STARLINE Forward Equalizers

Amplifier Setup 3-3

STARLINE Forward Equalizers

Select the appropriate model SFE-100-* to compensate for cable attenuation versus frequency and to obtain the proper output tilt. The BT100 is equipped with the BDR-1G interstage equalizer and flatness board, which compensates for cable attenuation. You must compensate for any cable or passive slope beyond that of the BDR-1G by selecting and installing the appropriate SFE-100-* cable equalizer.

Equalizers are available in 1 dB steps from 0 dB to 22 dB. The following examples describe how to choose the correct equalizer.

Example 1

The amplifier location includes 20 dB of cable (at 1 GHz) between its input and the preceding amplifier. Consider cable loss only. Exclude any flat loss due to splitters or other passive devices. The internal equalizer, model BDR-1G, compensates for approximately 14 dB of cable. Subtract this cable length from the 20 dB of this example (20 − 14 = 6). The SFE-100-6 is the proper equalizer in this case. With this equalizer installed, the amplifier reproduces the output tilt of the last upstream amplifier.

When selecting an equalizer, choose the next lower value if the exact value is not available or in cases where the calculated value makes two choices possible.

Example 2

The BT100 amplifier is used in a link following a fiber node. The fiber receiver output is flat and connects to the input of the amplifier through 18 dB of cable plus passive loss. Determine which is the proper equalizer to achieve 11 dB output tilt from the BT100.

Calculate the equalizer value using the following equation:

	SLOPEeq	= TILTout + SIGlo – SIGhi – SLOPEieq
where:	SLOPEeq	= required SFE-100-* slope
	TILTout	= required amplifier output tilt
	SIGlo	= signal input level at 54 MHz (channel 2)
	SIGhi	= signal input level at 1 GHz
	SLOPEieq	= interstage equalizer slope (14 dB)

From various references, such as manufacturer’s catalogs, you can determine that at an operating frequency of 1003 MHz, 18 dB of cable produces approximately 3.6 dB of loss at 54 MHz. This suggests that the channel 2 signal input to the BT100 is 14.4 dB greater

(18 − 3.6 = 14.4) than it is at 1003 MHz. Our example assumes that the high-end frequency level into the BT100 is +12 dBmV.

Substituting this information into the above equation provides the following result: 11 dB + 26.4 dB − 12 dBmV − 14 dB = 11.4 dB

The slope of the required equalizer is 11.4 dB. Table 3-1 and the graph in Figure 3-1 show that

11.4dB of slope is caused by approximately 14 dB of cable at 1003 MHz. Therefore the correct equalizer is model SFE-100-14.

When selecting an equalizer, choose the next lower value if the exact value is not available or in cases where the calculated value makes two choices possible.

BT100 Installation and Operation Manual