Presentation by Larry Wolcott of Comcast on proactive network maintenance (PNM) and Full Band capture (FBC). Find water soak coaxial cable. Find out more on our site.

1. Water Soaked
Drop Cable Signatures
Comcast OpTek
07/14/2020

2. Non-periodic attenuation
signature indicates water
Most downstream channels
Are bad, MER in the 20s

3. Single water signature detected, isolated to one customer

4. Customer Perspective
• Working from home, critically depends on reliable service
• Intermittent service was causing problems
• Tried swapping cable modem
• Many self-service attempts
• Comcast recommended resetting cable modem
• Was very happy to see us there!

5. What we Found
• 95’ RG6 drop, mfg. date 2016
(measured using jacket markings)
• Drop cable was strung over the
top of power main
• The coax was rubbing against
the power line when the wind
blew it

6. Outer jacket damaged,
allowing rainwater to
enter and soak the cable
Water pouring out
of the RG6 drop
at the ground block

7. Water signature in
Riser Bond TDR
Model 1550
TDR Results
• Velocity of propagation
(VoP) and distance
became unreliable
• VoP adjusted from 0.85 to
0.52 to maintain 95-foot
cable measurement
• -39% propagation over 95
feet of relatively new RG6
drop cable

8. 100% of the downstream
channels now have MER > 40 dB!
RF spectrum is nearly perfect
after 95-foot drop was replaced

9. Conclusion
• Water signature is easy and reliable to detect
• Almost always outside of the customers’ homes
• Facilitates socially isolated repairs
• Can be addressed with business partner workforce
• Gets worse in rainy weather / seasonal
• Causes poor customer experience
• Signatures can be detected prior to failure (proactive repair)
Next Steps
• National report of impairments by regions
• Trouble call, customer contact, repeat analysis
• Field trial and analysis of 200 accounts

10. Meanwhile, back at the lab..

11. Lab RF Verified
95’ RG6
Unimpaired Drop
Cable
95’ RG6 Water
Soaked Drop Cable

12. Speed Test of the 95 Foot Water Soaked Drop Cable
Speed Test of the 95 Foot New RG6 Drop Cable

13. What Happens When This Cable Freezes?

14. Freeze Test
95’ RG6 Frozen
Water Soaked Drop
Cable
95’ RG6 Thawed
Water Soaked Drop
Cable

15. Speed Test of the 95 Foot Thawed Water Soaked Drop Cable
Speed Test of the 95 Foot Frozen Water Soaked Drop Cable

16. Sample Processing, Step 1, Acquire

17. Sample Processing, Step 2, Interpolate and Smooth

18. Sample Processing, Step 3, Snip to 4096 Bins

19. Sample Processing, Step 4, IFFT and Trim to 128 Points