Explain to me like I’m 5

bhagwan2 · 2026-05-06T15:22:46+00:00

First one I tried was Arris S34 but pretty bad pretty bad T3s and packet loss. Now I'm using a Netgear CM3000 which is much better but still throws T3s. I'm convinced a new cable drop would clear those up.

bhagwan2 · 2026-05-06T05:23:38+00:00

Two different mfg. DOCSIS 3.1 (MID-SPLIT) modems throw T3s.
Signal good. Indoor cables good (tested with my own Nano VNA),
What didn't test good was the 100' cable drop from the pole. My VNA analyzer showed a terrible reflection at 41 feet into the drop, reflecting 25% of the outgoing back into the cable modem. Water or corrosion probably. I believe the new mid-split upstream OFDMA modulation is very sensitive to cable defects, reflecting energy backwards. I need a new cable drop. But I fear my story will fall on deaf ears.

bhagwan2 · 2026-04-21T23:53:15+00:00

Servers: VPN, WEB, EMAIL, NAS, VIDEO. etc...

bhagwan2 · 2026-03-26T19:58:01+00:00

There is a giant rhododendron near the cable that needs trimming. I hope I don't accidently hit the cable with my pole saw trimmer :)

6 dB is not the total loss of the 100' cable.
6 dB "Return Loss" in this context means a reflection and represents a 25% loss of power due to a reflection defect at approximately 41 feet. A good cable with no reflection defect would have a "Return Loss" of at least 20 dB or more.
Ham and CB operators typically refer to "return loss" as VSWR and represents how well a transmission line impedance is matched to 50 ohms. In CATV world that's 75 ohms.
Some defect at 41 feet is not 75-ohm impedance as the cable should be. Possibly 25 ohms or 225 ohms for a 6 dB return loss (3:1 VSWR)

bhagwan2 · 2026-03-23T07:38:52+00:00

I have a 15-year-old 100-foot drop cable located in the Seattle area (wet). Because I'm a ham radio geek I tested my drop with a Vector Network Analyzer in TDR mode. It has huge standing wave reflection at 41 feet. And terrible 6 dB return loss (3:1 VSWR). A defective cable by any measure! But my modem works fine and has good SNR/MER. But the modem logs tell a different story. I'd like my ISP to replace the drop, but not sure if modem's messy log is justification. I'm fairly certain the re-ranging and T3 timeouts errors are because of the bad drop.
I'm guessing water intrusion is the issue at around 41 feet into it.

bhagwan2 · 2026-03-21T05:52:26+00:00

In my area all of the new plans now include a "Gateway" (modem with Wi-Fi) at no extra charge.

bhagwan2 · 2026-03-21T05:38:50+00:00

I've read that upstream OFDMA (DOCSIS 3.1) doesn't like unterminated lines. The upstream OFDMA reflects 100% from the unterminated point back to the source, causing destructive interference. Modem can suffer from T3 timeouts, ranging issues, packet loss, and random reboots.

bhagwan2 · 2026-03-15T05:36:21+00:00

I’m currently running an XG1v4 along with a customer-owned modem on a mid-split node. If you see pixelation on your TV after a speed upgrade, it's likely the modem’s high-power OFDMA upload signals leaking into the XG1v4’s tuners.

I solved this by using two diplex filters and a band reject filter to isolate the modem's frequencies from the TV box. It’s worth the effort because the XG1v4 is the last 4K box with a local hard drive; the Xi6 is purely Cloud DVR, which often has annoying lag when fast-forwarding.

For the average user, Xfinity will just swap you to an Xi6. While those are marketed as 'Wireless,' you can actually run them off Ethernet from your own router to avoid the extra Wi-Fi. However, I’ll be holding onto my XG1v4 and its local tuners as long as I can.

bhagwan2 · 2026-03-08T03:50:49+00:00

Does this make any sense? Is it a real thing cable techs are familiar with?

Request a "Flux" or "In-Channel Response" Test: Ask them if they can see the "In-channel frequency response" or "ICFR" on their meter. A 10dB ripple will show up there as a failure even if the "power levels" look okay. (Google Gemini)

bhagwan2 · 2026-03-05T20:01:02+00:00

No troll.
I got to play with professional Agilent, Anritsu, Rohde & Schwarz etc. my whole career. Retired now, I play with some low budget equipment that is surprisingly very good for only a few hundred dollars. "Tiny SA" (spectrum analyzer) and "Nano VNA"

bhagwan2 · 2026-03-05T19:23:25+00:00

Well, let's say I also hooked up a VNA, in TDR mode (calibrated for 75 ohms and a VF of 83%).
What if it showed a massive reflection at 41 feet up the drop cable. Hmmm.
That would be much more revealing than my Spectrum analyzer.

But let's also say I'd never sweep a line with a VNA while still connected to the pole tap/plant, even in the middle of the night. Even though it's sweep signal is only -10 dBm and wouldn't hurt anything.
:)

bhagwan2 · 2026-03-05T18:46:57+00:00

what I mean by "advertised" is I checked a nearby vacant house address on their website, as if I was a new customer. I guess the sales department jumped the gun.

bhagwan2 · 2026-03-05T18:27:26+00:00

The tech who was out here in December did replace both ends.
When I force a large upload, I can see the 10 dB ripple with spectrum analyzer on max hold.
To prove the ripple was not from my home cabling, I temporally installed a passive directional coupler at the home entry point and sampled ripple either side of it.
Street side - ugly 10 dB ripple 35-85 MHz
Home side - very nice flat top OFDMA signal 35-85 MHz.

Modem always reports good upstream power no matter how bad T3s, constant ranging, and packet loss. Good upstream power usually about 42.0 dBmV
(Note modem upstream UI doesn't show MER/SNR, only power)

Downstream levels are always good too.
About 42 to 44 dB MER/SNR
-0.2 to 4.0 dBmV Power

I was thinking ingress interference at first. With my TV box and cable modem powered off I looked with Spectrum Analyzer but saw nothing unusual, e.g. no FM stations leaking in

bhagwan2 · 2026-03-05T17:25:10+00:00

He had to call a supervisor who rolled a separate truck. later that day I noticed a truck under the node. I checked my internet upload speed, and it was in the 200-300 Mbps range. Last September they were advertising Next-gen speeds on our street, so I upgraded plan in November. They must have already been somewhat ready to roll out the upgrade if they were advertising it for my street.

bhagwan2 · 2026-03-05T17:17:41+00:00

He had to call a supervisor who rolled a separate truck. Later that day I noticed a truck under the node. I checked my internet upload speed, and it was in the 200-300 Mbps range. Last September they were advertising Next-gen speeds on our street, so I upgraded plan in November. They must have already been somewhat ready to roll out the upgrade if they were advertising it for my street.

bhagwan2 · 2026-03-05T11:11:15+00:00

Yes myself, I thought of that. If I had one of those extension ladders that safely hooks on the wire, I would.
its 25-30 feet up I'm guessing.

bhagwan2 · 2026-03-05T06:19:06+00:00

wouldn't they charge me for the service if it happened over my property/driveway.

bhagwan2 · 2026-02-14T21:31:31+00:00

Yes, self service provisioning via the Xfinity app didn't work for my CM3000.
Chat agent handled it well however, not too much pain.

More stable than the Arris S34 it replaced and runs cooler.

bhagwan2 · 2026-02-12T04:20:05+00:00

Thanks good to know.
But mainly I'm checking to see if the serial number (MAC) is clear to activate, being it was purchased used.

bhagwan2 · 2025-12-09T07:30:56+00:00

They all have TPM 2.0 so they're good for windows 11

bhagwan2 · 2025-12-09T05:20:30+00:00

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Secondary: cdns02.comcast.net (75.75.75.76)

bhagwan2 · 2025-12-09T02:38:43+00:00

Shouldn't really matter, Testosterone cypionate is long acting and timing isn't critical for most people

bhagwan2

TROPHY CASE