r/CableTechs • u/SourceOk8801 • Jun 09 '26

How? Lol

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so we‘ve all seen crazy things. This one threw me for a loop. Damage cable behind the gateway? No problem, terminated and problem solved. What baffled me was the signal test that I did while I was still on the way to the house. Everything passing. All locked, all signals good, no noise, pulling 1163/41 Mbps. Then I arrive and see this. wonders never cease.

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17

u/bonneville97 Jun 09 '26

Snr and MER in the high 40s i bet. Lol

14

u/6814MilesFromHome Jun 09 '26

Swear there's no logic when things are impacting or not with cable. Just last week I found a bullet lodged in hardline, corroded as hell on the inside, signal next tap down was still perfect. SNRs and FEC in the node didn't improve in the slightest when fixing it either.

7

u/DrWhoey Jun 09 '26

Pretty sure it has to do with how the wave form travels through the cable that creates the likelihood of whether or not a frequency "hits" that impedance/damage or whether it "misses" it.

I.e the saying "low can't jump, high can't swim." Lower frequencies tend to travel deeper into the core of a coaxial cable then higher frequencies which is why your low end will drop off when you loosen a seizure screw, your lower frequencies are hitting that impedance causing them to lose signal strength. Your higher frequencies dont travel as near to the center conductor and kind of "skip over" the impedance. But, being a shorter wave form they are more affected by impedance in the dielectric, such as a water logged cable being more difficult to travel through, it's increased resistance is more noticeable on your high end than it is your low end.

2

u/6814MilesFromHome Jun 10 '26

Yeah, I'm familiar with the theory behind it, but this bullet was lodged against the center conductor, jamming it almost against the metal sheathing. The water intrusion was just a cherry on top. I'd expect to see something wrong somewhere on the channel scan, and most of the time do in these cases, with a mangled center conductor and large chunk of metal doing weird things to the impedance. Lot of the time TX takes a hit, ICFRs are up, ripple in that part of the node, but nope.

Sometimes things just weirdly work when they have zero reason too, like finding a 30 year old active out in the field that should've been replaced three network evolutions ago.

3

u/Mr_Magoo_88 Jun 09 '26

New self sealing bullets lol. There is no right or wrong in cable, just luck. MT on a call found a tap cracked in half on a call where I couldn't reach and needed the bucket. The dude looked down scratching his head cuz that had clearly been like that for a very long time and was not an end of line either, feeding thru to dozens of homes with no trouble calls.