# Check Signals on Modem



## kevinturcotte (Dec 19, 2006)

Time Warner FINALLY came out and disconnected the TV portion of their signal, but left the internet on (Like they were supposed to). How can I get into the modem and check signals and stuff (I've done it before, a long time ago)? It's a Cisco 2203C modem.
What levels of signals SHOULD I be seeing?


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## dpeters11 (May 30, 2007)

Connect to its IP address from your browser. Try username admin and password admin

Other than that, I don't know. When my ISP came to upgrade my service, I disconnected their box as soon as he left.


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## kevinturcotte (Dec 19, 2006)

dpeters11 said:


> Connect to its IP address from your browser. Try username admin and password admin


Okay, that let me get into it (Had to do a Google search to figure out the IP address on the modem lol). These are what it's giving me:

Receive Power Level 6.5 dBmV

Transmit Power Level 41.5 dBmV

Downstream Status Operational

Channel ID 22

Downstream Frequency 621000000 Hz

Modulation 256QAM

Bit Rate 42884296 bits/sec

Power Level 6.5 dBmV

Signal to Noise Ratio 38.4 dBmV

Upstream Status Operational

Channel ID 2

Upstream Frequency 25100000 Hz

Modulation 16QAM

Symbol Rate 2560 Ksym/sec

Power Level 41.5 dBmV

These good? Bad?


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## Matt9876 (Oct 11, 2007)

Acceptable cable modem signal levels.

Downstream (Rx) Receive Power Level:
This is the amount of signal received by the modem from the transmitter in the cable company head-end.

For all modems:
-15 dBmV to +15 dBmV maximum.
-12 dBmV to +12 dBmV recommended.

0 dBmV is the "optimal" level.

Upstream (Tx) Transmit Power (a.k.a. Return Signal) level:
This is the amount of signal transmitted by the modem to reach the receiver in the cable company head-end.

+8 dBmV to +58 dBmV maximum for QPSK. (DOCSIS 1.x)
+8 dBmV to +55 dBmV maximum for 8 QAM and 16 QAM. (DOCSIS 1.x)
+8 dBmV to +54 dBmV maximum for 32 QAM and 64 QAM. (A-TDMA DOCSIS 2.0)
+8 dBmV to +53 dBmV maximum for S-CDMA DOCSIS 2.0 modulation rates.

Recommended upstream signal levels are +35 dBmV to +52 dBmV.

A cable modem running a higher upstream modulation rate may downgrade itself to a lower modulation rate (i.e. 64 QAM to 16 QAM or 16 QAM to QPSK) if the upstream transmit level is higher than the maximum signal level allowed for the higher modulation rate and the CMTS is configured to allow such a change. This downgrade can cause slow speed, packet loss, and connection loss issues depending on the condition of the upstream channel.

A house or drop amplifier will NOT fix upstream signal problem because most house amplifiers don't amplify the upstream signals, they only pass the upstream signal through with some loss.

SNR (signal to noise ratio) levels:
This is how clear the signal is at either the modem receiver (downstream SNR) or the receiver in the cable company head-end (upstream SNR).

DOCSIS specifications list minimum CNR (carrier to noise ratio) levels not SNR levels. The SNR levels listed here are based on commonly recommended MER levels for digital cable signals. Not all QAM demodulator chipsets accurately calculate SNR levels that approximate actual MER levels, so these levels may vary depending on which chipset and/or firmware is used in the equipment.

QPSK: 12 dB minimum. 15 dB or higher recommended. (often used in upstream channels)
16 QAM: 18 dB minimum. 21 dB or higher recommended. (often used in upstream channels)
64 QAM: 24 dB minimum. 27 dB or higher recommended. (often used in downstream channels)
256 QAM: 30 dB minimum. 33 dB or higher recommended. (often used in downstream channels)
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Your setup looks good !


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