What is Tilt?

1. What is Tilt?

2. Definition Tiltis the effect of non-linear attenuation across the broadband spectrum. There are two varieties of tilt: forward tilt and reverse tilt.

3. Forward Tilt Forward tilt is a response where the low frequency carriers are lower in amplitude than the high frequency carriers. Below is a representation of a forward tilt. Note: The output of an amplifier is set up this way to overcome the higher losses of high frequency carriers as they pass through cable and passive devices. Ch.139 Ch.3

4. Reverse Tilt Reverse Tilt is a response where the low frequency carriers are higher in amplitude than the high frequency carriers. This is a product of attenuation. Since high frequency carriers attenuate faster than low frequency carriers, a reverse tilt will occur as carriers travel away from the amplifier. Below is a representation of reverse tilt. Ch.3 Ch.139

5. Broadband Network Example • Below is a representation of how forward and reverse tilt occurs in the broadband network. AMP AMP

6. Tilt At the Active (note; tilt is based upon analog signal level, if the highest channel/frequency is digital then add 6dB to convert it to analog to get an accurate linear tilt.)

7. Tilt At the Premise (note; tilt is based upon analog signal level, if the highest channel/frequency is digital then add 6dB to convert it to analog to get an accurate linear tilt.)

8. Measurement • Tilt is measured by taking the difference of the levels, i.e., if Ch. 139 was at 50.5dBmv and Ch. 3 was at 38dBmv then the tilt would be 50.5-38= +12.5 dB of positive tilt. (Industry Standard to high channel/frequency over low channel/frequency) In this example because the higher channel/frequency was at a higher level (50.5dBmv) it would show forward tilt. If the opposite was true such as Ch. 139 was at 19dBmv and Ch. 3 was at 23dBmv. The tilt would be 19-23= -4dB, but because the lower channel/frequency was at a higher level (23dBmv) than this would be reverse tilt.

9. Roll-off • Unlike a reverse tilt, a roll-off is an obvious change in attenuation causing the amplitude of the carriers to roll off sharply as opposed to a gradual tilt. Water damaged equipment and cables, and using the wrong bandwidth gear causes this kind of a roll-off.

10. Roll-off cont. • Faulty diplex filters may cause a roll-off at the front end of the spectrum.

11. EOL tap tilt specifications • Tilt shall not exceed 3 dB positive or negative from system design. (Tilt measured between high and low analog carrier.) This may be an indicator of HFC plant alignment issues. If you questions about the tilt on a job you are on please contact an FNT partner. • If tilt does not meet allowable standards a plant check ticket shall be created to verify proper amplifier balance as well as LEQ installed and operational. • This step is required to prevent masking of system problems Motorola 5101 modem tilt

12. What is in your control? RG-6 vs. RG-11 The attenuation difference between the high and low frequencies with RG6 is greater than with RG11 or feeder cable, 6.1dB per 100’ @ 1GHz and 1.6 per 100’ @ 50MHz on RG6 compared to 3.98 per 100’ @1GHz and .96 per 100’ @ 50 MHz in RG 11, therefore tilt will change at a faster rate. With the use of RG6 your negative tilt will be 1.5 dB higher per 100’. Distance 100' 50mhz1ghz RG-6 1.6 6.1 RG-11 .96 3.98

13. Questions / Comments / Concerns ??????? Motorola 5101 modem tilt