[PVRCNC] Time Warner Cable Modem RFI

[Brian Alsop]

Guys,

Some repair work out here by TWC resulted in among other things a 
replacement internet/digital phone modem. (uplink speed went to near 
zero and signal levels were down 10db from acceptable)  It's a 
Touchstone Telephony modem and generated about 10-15db of noise above 
the noise floor on 20-10M.  The previous Motorola unit was quiet. 
Thinking it was power line noise as a result of the recent storm,  I 
tracked it down first with a beam pattern plot then an AM radio.  The 
thing buzzed like a chainsaw.  Wrapping the modem in aluminium foil 
reduced it to barely detectable on the above bands.  This modem doesn't 
seem to heat up while tented.  I suspect it is the (now internal) 
switching power supply.  Unplugging it works too....

If you have a quiet modem, don't let them do this replacement.  Or make 
sure they don't leave before you've checked it out for RFI.

Other things of note.  The uplink frequency is now 25MHz!  Hmm, a KW ERP 
on 24.9 hasn't clobbered it yet.  Previously it was at 33 MHz.  I 
thought this was selected almost on a random basis from available slots 
upon modem startup.  Several tries at restarting always resulted in 
25MHz for the uplink.  This low frequency allows for little bandwidth 
and is probably why one gets only 1 mbps upload speed.  In case you're 
interested the modem is now operating on these frequencies and modes:
1)Downlink 621MHz, QAM256 -2dbmV
2)Uplink 25MHz, QAM16 2560kSym/sec, 31dbmv.

The serviceman worked from blocks away to the house and found several 
corroded connections, significant cable leakage and an extra 
unterminated splitter in my connection box. He also frowned on the Radio 
Shack F connector I made up after destroying one of theirs with an 
electric drill.  A second crew came out later and reset signal levels to 
normal.

I'm going to be talking to TWC about this when I get back from FL.
It will be interesting to hear what they have to say.

Any suggestions of what kind of leverage I can use to resolve this would 
be welcome.

73 de Brian/K3KO


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Version: 2012.0.2238 / Virus Database: 2639/5585 - Release Date: 02/06/13