From the Field: Five Things I Wish I'd Known as a Cable Contractor
In 2007, I started my cable career as a contractor. I performed residential installs and service calls. After my first five years, I knew I had a lot of experience and could accurately diagnose a problem (the hard way). Now that I’m a plant maintenance tech for the fifth-largest cable company in the country, I realize that back then I didn’t know squat. So, with that in mind, here are a few things that I wished I’d known as a contractor that I know now.
First is learning how to use my expensive meter to my advantage instead of just, “Have I got a signal here or not?” There are many features on these meters that can help me track down an issue accurately and efficiently. So, it turns out each TV channel loads on a certain frequency. I can find that frequency in the diagnostic page of a cable box. Then, I can pull up that frequency range on my fancy meter, as a digital channel, and it will tell me important information about it if I can decipher it. Once I learned how to do this, it saved me significant time versus running a “hot drop” from the tap to the cable box to bypass the house wiring for troubleshooting. With my meter, I can test any location and identify where it is good and where it is bad, then make the repair. This leads me to the second and third things I wish I’d known as a contractor: Modulation Error Ratio (MER) and Bit Error Ratio (BER).
MER and BER provide vital information for tracking TV and data issues such as tiling, blacking out pictures, voice cutting out on a phone, and slow internet. But, as a contractor, I had no clue what MER and BER were and how knowing about them can help me. So, let me explain what they are while keeping this as short and simple as possible. MER, similar to signal-to-noise (SNR), shows you the signal quality. With MER, the higher the better! Once MER drops down to 28 dB and below, the data transmission is lost. In fact, anything in the low 30 dBs is getting sketchy on today’s 256-QAM digital channels. The industry does not accept anything lower than 35 dB directly off the tap. Many companies don’t accept anything under 32 dB MER at the equipment. Issues with MER can be fixed on the drop side of the cable by locating issues, such as loose connections, Ingress getting into cables, tilt, corrosion, and low-quality splitters and cables. BER is, in a nutshell, the loss of packets (loss of 1’s and 0’s). For example, this is your actual tiling on the TV. There is not enough correct 1’s and 0’s to give you the correct image. There are pre-BER and post-BER. Pre-BER is total packet loss in getting to that location. Post-BER is what packet loss is left after the equipment corrects it (which ultimately shows up as tiling, and cutting out of voice and data). While pre-BER is not service affecting, post-BER is.
Next, we have tilt. Wait, what? Nobody has ever mentioned the word “tilt” before. What in the world is tilt and how does it affect the cable? Well, it turns out that if a channel is stronger than another channel, it will over power it and cause its MER to drop. For example: Ch. 2 is 10 dBmV, Ch. 3 is 15 dBmV, and Ch. 4 is 10 dBmV. Ch. 3 is going to lower the MER of Ch. 2 and CH. 4 because it’s much stronger than the other two. This also works on a bigger scale. Compare the whole spectrum of available signal coming to a house. Let’s say the lowest channel is Ch. 2 (57 MHz) and the highest is Ch. 156 (981 MHz). These two channels are very far apart with well over 150 active channels separating them. But, if Ch. 2 is more than 5 dB stronger than Ch. 156 and, assuming the whole spectrum is tilted in a linear fashion, it will start lowering the MER on Ch. 156 and the other channels near it. This is called reverse tilt and it is represented as a negative number. I couldn’t tell you how many homes I’ve walked into with intermittent tiling issues that had 15 dB or more reverse tilt. The longer the cables and the more splitters you add, the worse this “tilt” gets due to more signal loss on the higher frequencies. It wasn’t until I went in-house for over a year that I figured out an inline equalizer exists and how to use it to correct reverse tilt in the home.
The fifth thing I wish I’d known more about is upstream. It wasn’t until I became a maintenance tech who frequently monitored and fixed upstream issues did I realize that our 5-40 MHz spectrum is very much alive and breathing. It’s always changing and wreaking havoc. From one random loose fitting on the back of a modem, to a dog-chewed cable, to one loose seizure screw on the side of a tap out of literally thousands of possible screws, is all it takes to take down a whole node. It’s a never-ending battle. I couldn’t tell you how many houses I have gone to where they complained of the Internet not working and, of course, it works fine while I’m there that day and everything tests fine (as far as I knew). But these days, cable companies have a lot of tools at hand to help track upstream noise issues. I would have been able to diagnose a lot of houses with upstream issues without having to come back to the same house repeatedly to find nothing wrong.
Being a plant maintenance tech has helped me grow my cable knowledge tremendously over the last few years. If I could only get my knowledge out there to help those cable techs who want to learn, then it would be a win-win-win situation for the tech, the customers, and the company. A happier customer, due to more accurately diagnosed issues, equals increased value.
Dosty Hedges is a 10-year cable veteran who works out of the Arizona desert, five years of which was spent as a contractor performing residential installs and supervising others. He is currently a Field Network Operations Tech 2, clearing outages and maintaining a cable plant. Mr. Hedges has completed Service Technician, System Technician, and Return Path Operations through NCTI.
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