Cable modem signal, is it Digital or Analog?

[ucvb6]

Sorry for the newb question. I have cable modem service and don't know if it's Analog or Digital.

 

[spidey07]

I assume it is an analog carrier frequency.

Don't know much about cable broadband.

 

[Genx87]

believe the signal is analog

 

[qaa541]

The signal over the coaxial cable is analog, but it is digially encoded by the cable modem and decoded by the CMTS

 

[Rifter]

Analog into the modem.

 

[Ichinisan]

This thread...ugh!

The coaxial cable can carry analog and digital signals simultaneously (on different frequencies). DOCSIS 3.x cable modem signals are purely digital. Most cable companies have eliminated all or nearly-all of their analog TV channels. They can get four or more digital channels in the same spectrum slice that was previously occupied by a single analog channel (at least two 1080i channels with high bit rate and inefficient MPEG2 codec). More of those frequencies that had previously been occupied by TV channels can be used to load-balance cable modems. Furthermore, instead of broadcasting all TV channels simultaneously to all subscribers regardless of which channels are being watched, most cable companies have converted to a switched-digital system.

 

[Mr Evil]

At the physical layer, everything is analogue. The circuitry for sending the signal over the cable and receiving it at the other end will all be analogue. The data encoded by the signal is digital of course.

 

[Ichinisan]

At the physical layer, everything is analogue. The circuitry for sending the signal over the cable and receiving it at the other end will all be analogue. The data encoded by the signal is digital of course.

Still, most people refer to WiFi or wired cat-5E networking as "analog." Same with digital signals over coax -- don't call it "analog."

 

[aigomorla]

OMG who necro'd this thread? :\

14 yr old thread....

 

[VirtualLarry]

DOCSIS 3.x cable modem signals are purely digital.

No, they are an analog encoding of digital data using QAM, I believe.

 

[JackMDS]

https://en.wikipedia.org/wiki/Digital_cable

 

[Ichinisan]

No, they are an analog encoding of digital data using QAM, I believe.

They use QAM-64 and QAM-256 as a way to slice up the frequency spectrum. The signals transmitted in those QAMs are digital. No reason to ever be analog.

WiFi / LTE / GSM / CDMA / ATSC / DVB / DSL...we don't call those "analog."

 

[Hi-Fi Man]

They use QAM-64 and QAM-256 as a way to slice up the frequency spectrum. The signals transmitted in those QAMs are digital. No reason to ever be analog.

WiFi / LTE / GSM / CDMA / ATSC / DVB / DSL...we don't call those "analog."

It's a bit semantics but in the world of RF typically anything using a sine wave is considered an analog transmission even though it uses modulation to represent a digital signal if that makes any sense. Since sine waves can theoretically represent an unlimited amount of values; they are considered analog. I would also say all of the above standards use analog transmission and are digitally modulated.

QAM does not "slice up the frequency spectrum", instead it is a form of amplitude modulation (AM). You may be confusing QAM for FM.

Source: Me, RF systems tech in the USAF and AS in said field.