Motorola SurfBoard DOCSIS 3.0 Cable Modem
$39.99
$59.99
33% off
Reference Price
Condition: Factory Reconditioned
Top positive review
4 people found this helpful
Smaller, Faster, and Better, too !!
By Rust Never Sleeps on Reviewed in the United States on August 4, 2012
I was one of the first to get a Motorola SB6120 -- and was very much satisfied with the ease of set-up, the awesome speeds, the functionality, and the workmanship. But, like all electronic gizmos, they tend to crap out after a few years. When my SB6120 started dropping upstream channels, I looked to Motorola once again -- right here at Amazon -- and found the new Motorola SB6121. After checking the specs, I found that the new SB6121 Model has the latest IPV6 technology (higher bandwidth capabilities)that were not available on the SB6120. The newer IPv6 technology allows connection speeds up to 160 Mbps., against the 150 Mbps of the SB6120. IPV6 is not in common usage yet, but it will be pretty soon -- And the SB6121 will be ready with the fastest speeds available!! The new SB6121 is a super-easy set-up, and the connection speeds are fast and steady. Comparing the DOCSIS 3 SB6120 to the newer SB6121 : 1.- The Sb6121 is smaller (height and depth are smaller, width is greater). 2.- The SB6121 runs slightly (average about 5 degrees F) warmer than the SB6120. 3.- Connection speeds, latency, and jitter are better with the SB6121 than the SB6120 -- and WAY faster than ANY DOCSIS 2 modems, regardless of manufacturer. Some tips I learned from using the Motorola DOCSIS 3 Modems with 2 different (D-Link DIR-655 and Netgear WNR3500L) "N"-speed Wireless Routers: The SB6120 runs coolest when mounted to a wall or other vertical surface, and spaced approximately 1/2-inch away from the surface. This allows an adequate air flow that's necessary to keep the Modem cool. Mounted with the wires pointing straight down, the SB6120 runs at about 95 degrees F in a 78 degree room when mounted away from a wall. Temperatures measured with Mastercool Infra-Red Laser Thermocouple Gun (available at Amazon). The new SB6121 is smaller than the SB 6120, and it runs a little bit warmer (98-100 F), even when mounted the same way as the SB6120. I suggest that you mount the new SB6121 1/2" away from the wall as well, but with the wires pointing straight back. Whatever you do, DON'T STACK ANYTHING on ANY Modem or Router !! Both of these devices give off heat and electrical interference, and will perform their best when spaced about 4 feet apart, which keeps the interferences from overlapping and killing the Wireless Router's range. When you get your internet connection going, go to the Motorola Modem's Home Page: Sample snapshot of my SB6121 = Cable Modem Status Signal Addresses Configuration Logs Open Source Help This page provides information about the current upstream and downstream signal status of your Cable Modem. -------------------------------------------------------------------------------- Downstream Bonding Channel Value Channel ID 49 50 57 58 Frequency 837000000 Hz 843000000 Hz 861000000 Hz 867000000 Hz Signal to Noise Ratio 37 dB 37 dB 38 dB 38 dB Downstream Modulation QAM256 QAM256 QAM256 QAM256 Power LevelThe Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading -1 dBmV -1 dBmV -1 dBmV -1 dBmV Upstream Bonding Channel Value Channel ID 3 1 2 Frequency 36100000 Hz 23300000 Hz 29600000 Hz Ranging Service ID 7425 7425 7425 Symbol Rate 5.120 Msym/sec 2.560 Msym/sec 5.120 Msym/sec Power Level 45 dBmV 45 dBmV 45 dBmV Upstream Modulation [3] QPSK [3] 64QAM [3] QPSK [2] 16QAM [3] 64QAM [3] QPSK [3] 64QAM Ranging Status Success Success Success Signal Stats (Codewords) Bonding Channel Value Channel ID 49 50 57 58 Total Unerrored Codewords 1457238562 1457238645 1457237949 1457238150 Total Correctable Codewords 17 26 23 27 Total Uncorrectable Codewords 1031 937 1682 1468 -------------------------------------------------------------------------------- Status | Signal | Addresses | Configuration | Logs | Open Source | Help © Copyright 1997-2008 It should give a snapshot of the specs for YOUR modem. You will be looking for 4 Downstream channels that read SNR @ 37-38 db and the power levels at around 0 dbmV. Upstream power levels on all 3 bonding channels should read around 45-50 dbmV. A deviation of 5 from any of these figures indicates a problem. If the Modem's signal is solid and constant, but the power level readings are 5 points off in either direction, check your OUTDOOR SPLITTERS or TAPS first, because they tend to crap out when they're exposed to heat for long periods. The operating temperatures for splitters and taps is only 140 degrees F. maximum, and that temperature is easily reached in direct sunlight, even when enclosed. Those of you who live in hot climates may notice that the Modem's downstream power levels drop off 1 or 2 points when the outside temps get up to 110 F or higher. Don't panic !! In case of rapture, dial 1-800-Oh Jesus. ;>) I found the RCA DH24SP High-Bandwidth (5-2400MHz)2-Way Signal Splitter (available at Amazon) to be an excellent handler of the high-speed signals of Cable, Satellite, and HDTV signals. It's a "2-Way" splitter, so the power flows equally in either direction, enabling MUCH higher upload speeds. If you need a TAP for unequal cable lengths, a CommScope SV-DC-6G Digital Tap worked well for me. For strong and clear Wireless range and reception, use only Category 7 (shielded) Ethernet cable (available at Amazon) between your Modem and Router, and between your Router and Main computer. Good Luck !!
Top critical review
50 people found this helpful
The little modem that couldn't (cable modem reboot due to T4 timeout)
By Jeremy on Reviewed in the United States on February 10, 2013
Summary: this modem is fine if your service is good, but it fails really ungracefully if your service is marginal. While the underlying cause of the issue *is* poor service (which is of course no fault of the modem), fluctuations in signal quality are unavoidable, and how the device *handles* sub-optimal service must be considered in the review process. The fact that the modem reboots with even minimal signal degradation - in situations where other devices do not - is why I have arrived at a rating of 3 stars. The problem? When your signal levels drift out of spec even slightly, the SB6121 shoots itself in the head and reboots. The error recorded in the logs is "rebooting due to T4 timeout." When it reboots your service is interrupted for 30 seconds to a minute, while you wait for the device to boot and re-register with the CMTS. In my particular case, this behavior happened a few times a day. By way of comparison, my DOCSIS 2.0 modem never had this issue, and after preliminary testing my Zoom 5341J DOCSIS 3.0 modem does not either (although the jury is still out on that modem's long term performance. How much this bothers you depends both on how frequently it occurs and on how you're using your service. For normal web browsing, you may never even notice it. But this kind of intermittent loss of connectivity will wreak havoc on things which require a steady connection: online gaming, video streaming, telephony, work VPN, etc etc. If you'd like to know if this is happening to you, the logs are available at the modem's web management UI - look for "reboot" there and check your uptime on the main status page. I am (sadly) a Time Warner Cable customer. If you do happen to see this behavior with TWC, be warned: they will not do anything to help you, since such problems are generally very difficult for them to track down, and as a rule they are deemed too expensive for them to actually correct. They will either try to up sell you to ultimate/extreme/turbo/etc and claim that this will resolve the issue, or they will tell you to the modem is defective and suggest that you exchange the modem for a replacement. Do not believe the lies of these charlatans. Being provisioned for a higher cap will do nothing to avoid a time out like this (if anything, pushing more data might exacerbate it), and all SB6121s will handle these scenarios in the same way. A new one will not help. If you are aware of these issues and opt to try your luck with the SB6121, I recommend that you retain your "rented" modem for a period of time to verify that your level of service is adequate to keep the SB6121 happy. Wait at least a week, and check the logs: if you do not see T3 / T4 timeouts, you are probably fine. However, if you do see time outs and reboots, you should switch back to your "rented" modem and promptly return the SB6121 within Amazon's return period. Then, you should evaluate your options: if you are paying for and actually need a level of service which requires DOCSIS 3.0 speeds, try a different DOCSIS 3.0 modem such as the Zoom 5341J and cross your fingers. If you do not actually require DOCSIS 3.0 and do not intend to upgrade, though, DOCSIS 2.0 may very well prove more reliable for you and the modems tend to be cheaper. You cannot go wrong with something like the Motorola SB5101U, which should be much more tolerant of failed providers (and also, it should be in extensive deployment, so chances are if *you* see a problem, so will your neighbors - making your provider much more likely to actually start caring enough to fix it). One final note: I've read that some Comcast customers have received firmware updates which resolve this problem for them. However, be advised: only your cable provider can update the firmware of cable modems, and nobody I ever talked to at TWC seemed capable or interested in discussing firmware updates for my device. If you can get a firmware update that improves the stability of this modem, that's great, but at least with TWC you cannot count on them to do this for you. Below are some typical signal strength observations at my installation for both this device and the Zoom 5341J (which I replaced it with). Typical readings on the SB6121 (when operating normally): SNR: 36-37 dB (four channels bonded) Downstream power level: 3-4 dBmV (four channels bonded) Upstream power level: 46 dBmV (single channel) (Note: these readings are all within spec. When the device reboots the SNR is substantially lower (it's difficult to get precise data since the device retains no long term signal strength data)) Typical readings for the 5341J: SNR: 40-42 dB (four channels bonded)* Downstream power level: 2-3 dBmV (four channels bonded) Upstream power level: 46 dBmV (single channel) The important thing to note here is the improved SNR of the 5341J. I should reiterate that all of these values are within spec, and you would see absolutely no difference in performance from the 5341J's slightly better readings. However, the fact that the 5341J fares better in normal operation implies to me that the device is of a superior design, and it may tolerate conditions the SB6121 will not.
Sort by:
Filter by:
By -
Verified Amazon Purchase
Vine Customer Review of Free Product
Sorry, no reviews match your current selections.
Try clearing or changing some filters.Show all reviews
Show more reviews