[olug] mystifying cable modem problem

[Eric Penne]

In a 75 ohm system dBmV -49 = dBmW

-8dBmV = -57dBmW = 1.26nW (nanoWatt)
49dBmV = 0dBmW = 1milliWatt

One of the key issues is your signal to Noise ratio.  35dB is pretty good.

Craig Wolf wrote:
> Ok, I have: Downstream
> Signal to Noise: 35dB
> Power Level: -8dBmV
> Upstream:
> Power level: 49dBmV
> Symbol Rate: 2.560 Msym/s
> 
> Hope that helps as a reference...
> 
> Craig Wolf
> Linux Web Server Support
> Desktop/Network Specialist
> 402-894-6283
> 
> 
>>>>epenne at olug.org 08/31/04 11:50 AM >>>
> 
> -13dB really doesn't mean anything.  -13dBW is about 100 milliWatts. 
> Many wireless cards put out 50 - 100mW and you can still get on the 
> network for a long ways.  Imagine how far 100mW can go down a coax
> cable.
> 
> -13dBm is about 0.1mW.  I'm not sure but I believe this is plenty of
> power.
> 
> Eric Penne
> 
> Eric Pierce wrote:
> 
>>Exactly.  However, I'll try Ethereal out tonight.  It's good to try
> 
> out new
> 
>>shit.
>>
>>I tried Jay's suggestions (to have Cox remove and re-add my modem),
> 
> but that
> 
>>didn't work, and I tried resetting/standby/etc. the modem, but that
> 
> didn't work
> 
>>either.  I went to a popular electronics store and am currently
> 
> "leasing" a
> 
>>Motorola SB 5100 modem.  I had it provisioned by Cox, and I got right
> 
> on the
> 
>>network...  I could finally access the modem at 192.168.100.1, and I
> 
> noticed
> 
>>that the signal level was -13 Db.  Seems kinda low.
>>
>>The Toshiba modem I have has a 5 year warranty, so I'm going hit them
> 
> up on
> 
>>that.
>>
>>In the meantime, if anyone has an extra modem laying around for a
> 
> decent price,
> 
>>I'm interested.
>>
>>Thanks,
>>Eric
>>
>>
>>--- Terry <td3201 at gmail.com> wrote:
>>
>>
>>
>>>I think that if he would know how to do all that, he wouldn't be
>>>asking what ethereal is.  :)
>>>
>>>
>>>On Mon, 30 Aug 2004 22:18:07 -0500, Dave Hull <dphull at insipid.com>
> 
> wrote:
> 
>>>>Quoting Bill Brush <bbrush at unlnotes.unl.edu>:
>>>>
>>>>
>>>>
>>>>>1.  A 10base-T network can be switched also.
>>>>>
>>>>>2.  A 100base-T network can be run on a hub.
>>>>>
>>>>>3.  Even if the network is switch you can use a promiscuous port to
> 
> see
> 
>>>>>everything (on a managed switch).
>>>>>
>>>>>4.  On an unmanaged switch you can use certain tools to do Arp
> 
> poisoning
> 
>>>so
>>>
>>>
>>>>>your monitoring station can act as the man in the middle.
>>>>
>>>>>From what I hear, some switches "fail open" or revert to a hub like
> 
> mode
> 
>>>if they
>>>
>>>
>>>>are overwhelmed (buffer overrun?) or otherwise compromised. If you
> 
> can make
> 
>>>that
>>>
>>>
>>>>happen on the network in question, you can see pretty much
> 
> everything.
> 
>>>>--
>>>>Dave Hull
>>>>http://insipid.com
>>>>
>>>>
>>>>_______________________________________________
>>>>OLUG mailing list
>>>>OLUG at olug.org
>>>>http://lists.olug.org/mailman/listinfo/olug
>>>>
>>>
>>>_______________________________________________
>>>OLUG mailing list
>>>OLUG at olug.org
>>>http://lists.olug.org/mailman/listinfo/olug
>>>
>>
>>
>>
>>
>>		
>>_______________________________
>>Do you Yahoo!?
>>Win 1 of 4,000 free domain names from Yahoo! Enter now.
>>http://promotions.yahoo.com/goldrush
>>_______________________________________________
>>OLUG mailing list
>>OLUG at olug.org
>>http://lists.olug.org/mailman/listinfo/olug
> 
> 
> _______________________________________________
> OLUG mailing list
> OLUG at olug.org
> http://lists.olug.org/mailman/listinfo/olug
> 
> _______________________________________________
> OLUG mailing list
> OLUG at olug.org
> http://lists.olug.org/mailman/listinfo/olug