Modem Keeps Dropping Signal

Modem Keeps Dropping Signal

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Subject Author Date
Modem Keeps Dropping Signal Bruce 12-15-2005
Posted by Bob H on December 15, 2005, 10:28 am
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In my area (eastern WA. state) Comcast offers the moto. modem along with one
by the name of AMBIT, I saw it at a comcast booth in a home show & asked for
it when I moved, It is much smaller about the size of a dsl modem and
appears to be fast, I went from connect speeds of 3-4,000 to 7-9,500 whith
the change (granted I did move but from a new neighborhood to one with nuch
older lines).....we get 8,000 as cable subscribers here....anyway, since you
are renting your modem and having problems with the Moto. you might check
into it.

>
>> Bruce wrote:
>>> "Dr Feelgood" wrote:
>>>> Chances are it was not provisioned properly. Could be the mac
>>>> address was input wrong. Try giving service a call again and have
>>>> them double check it.
>>>>
>>>>
>>> If that were the case, I don't think I'd even get a connection.
>>>
>>
>> Not necessarily.
>>
>> Remember that both your computer and the modem have their own IP
>> addresses. Your computer may be getting a valid IP address because
>> it's MAC address is already on your account. When the modem comes
>> online for the first time, it should get an IP address that will only
>> allow local access, but once it's provisioned, it will get an IP
>> address that will allow access to the Internet. The problem is that
>> the IP address is initially assigned at the direction of the
>> provisioning system. It is a very short lease. When it comes time to
>> renew the lease, if the provisioning process has not finished, the
>> regular DHCP server won't recognize the modem as being allowed to have
>> a full-access IP address. Your online light will remain lit, but
>> you'll have no access to the Internet.
>>
>> It should be easy for this to be fixed. A customer service rep can
>> repush, or refresh, the information on the account, after which the
>> DHCP server for your node will now know to give your modem a
>> full-access IP. Assuming your modem's MAC is correct in the records
>> (which it probably is if you are able to get, and re-get, the
>> temporary IP address that allows you to keep getting online over and
>> over again for that hour time period.)
>>
>
> Thanks Warren and Dr. FG. I have had them push a new config file twice,
> but this time I asked them to check the MAC. It was correct. Comcast
> suggests possibly a bad modem out of the box, and to swap before the
> truck roll on Saturday. I'll try to get back to the Comcast store before
> then...
>
> Thanks again.



Pure Networks
Posted by $Bill on December 15, 2005, 2:18 am
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Bruce wrote:

> I'm in the SF Bay Area, zip 94070. I swapped out my RCA DCM245, which
> couldn't handle the new, higher speeds, for a Motorola SB5101 at the
> Comcast walk-in store. I now have the new speeds, but every hour or so,
> the modem drops the signal. The online light stays solid, but I'm no
> longer connected to the internet. I have to power cycle.
>
> Here's my modem stats for the new SB5101:
> Downstream
> Frequency 705000000 Hz
> Signal To Noise Ratio 27.8 dB (RCA was 35.2)
> Power Level -5.5 dBmV (RCA was -7.5)
>
> Upstream
> Channel ID 4
> Frequency 24800000 Hz
> Power 34.0 dBmV (RCA was 32)
>
> I've got a truck roll for Saturday morning to check line (that's what
> Comcast wants to do), but it seems odd that this happened immediately
> after putting the new SB5101 into service.
>
> I don't understand if this is a coincidence that the S/N dropped, or if
> the new modem could be the problem.

SNR a little low, but still should work.

Check all your connections and make sure you have good contact. What
devices do you have prior to the modem from the outside in ? How long
is your run to the modem ? If all if well, you may want to try a swap
on the modem.



Posted by Dr Feelgood on December 16, 2005, 2:04 pm
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I'm running an owned DCM 235r I bought back in 2000 and getting the full 8 meg
and then some. I just wish Comcast would take the UL to a full meg.

Thousands of users are using the rental SB5101's without a problem. Double check
your physical connections.

Is the truck roll still scheduled for tomorrow?


> I'm in the SF Bay Area, zip 94070. I swapped out my RCA DCM245, which
> couldn't handle the new, higher speeds, for a Motorola SB5101 at the
> Comcast walk-in store. I now have the new speeds, but every hour or so,
> the modem drops the signal. The online light stays solid, but I'm no
> longer connected to the internet. I have to power cycle.
>
> Here's my modem stats for the new SB5101:
> Downstream
> Frequency 705000000 Hz
> Signal To Noise Ratio 27.8 dB (RCA was 35.2)
> Power Level -5.5 dBmV (RCA was -7.5)
>
> Upstream
> Channel ID 4
> Frequency 24800000 Hz
> Power 34.0 dBmV (RCA was 32)
>
> I've got a truck roll for Saturday morning to check line (that's what
> Comcast wants to do), but it seems odd that this happened immediately
> after putting the new SB5101 into service.
>
> I don't understand if this is a coincidence that the S/N dropped, or if
> the new modem could be the problem.



Posted by Bruce on December 17, 2005, 12:32 am
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> I'm running an owned DCM 235r I bought back in 2000 and getting the
> full 8 meg and then some. I just wish Comcast would take the UL to a
> full meg.
>
> Thousands of users are using the rental SB5101's without a problem.
> Double check your physical connections.
>
> Is the truck roll still scheduled for tomorrow?
>
>
>> I'm in the SF Bay Area, zip 94070. I swapped out my RCA DCM245,
>> which couldn't handle the new, higher speeds, for a Motorola SB5101
>> at the Comcast walk-in store. I now have the new speeds, but every
>> hour or so, the modem drops the signal. The online light stays
>> solid, but I'm no longer connected to the internet. I have to power
>> cycle.
>>
>> Here's my modem stats for the new SB5101:
>> Downstream
>> Frequency 705000000 Hz
>> Signal To Noise Ratio 27.8 dB (RCA was 35.2)
>> Power Level -5.5 dBmV (RCA was -7.5)
>>
>> Upstream
>> Channel ID 4
>> Frequency 24800000 Hz
>> Power 34.0 dBmV (RCA was 32)
>>
>> I've got a truck roll for Saturday morning to check line (that's what
>> Comcast wants to do), but it seems odd that this happened immediately
>> after putting the new SB5101 into service.
>>
>> I don't understand if this is a coincidence that the S/N dropped, or
>> if the new modem could be the problem.
>
>
>

Yep, the truck roll is still scheduled for Saturday (tomorrow) morning.

If interested, check out this thread. It discusses the Motorola SB5101
and possible firmware problems.

http://www.dslreports.com/forum/remark,13568778?hilite=sb5101+research

Thanks,
Bruce

Posted by Eric on December 17, 2005, 5:20 pm
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>Signal To Noise Ratio 27.8 dB (RCA was 35.2)
>Power Level -5.5 dBmV (RCA was -7.5)

They changed the downstream to 256 QAM. The SNR is too low to support
reliable communication. You need to have a tech investigate. you may
need a new drop, or they need to set up the amplifiers in your
neibhorhood, as -5.5dB should get you somewhere around 35dB SNR or so,
unless you are at the end of a very long cascade.

Good luck.


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