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Posted by drydem on January 26, 2008, 11:50 am
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> On Jan 22, 12:17=A0pm, comph...@toddh.net (Todd H.) wrote:
>
>
>
>
>
> > > Thanks for the tip.
>
> > > I went to the local Radio Shack store and I purchased
> > > a Bi-Directional Cable TV 10db Amplifier (Radio Shack Catalog
> > > Number 15-2505) which is designed to allow for digital cable
> > > modems, digital TV, and pay for view services. =A0I replaced
> > > the older RF 20db Amplifer with the newer Bi Directional
> > > RF 10db Amplifier - while the cable channel signals were still
> > > usable/powerful -- =A0the cable modem was still unable to
> > > get an internet broadband signal in the office. =A0Why didn't
> > > it work? I'm not sure.
>
> > There are a few possibilities. =A0You're (admittedly) using the wrong
> > cable, you're crimping your own connections, using a Radio Shack
> > amplifier and a Home Depot 3-way splitter. =A0It's amazing you get TV
> > much less cable modem signal. =A0:-)
>
> > May I suggest a more methodical approach?
>
> > Let's start by plugging the cable modem in where it last worked. =A0Look=
> > at the web page athttp://192.168.100.1wheremost DOCSIS modems will
> > have a signal page somewhere... and record upstream power level,
> > downstream power level, and signal/noise ratio (SNR). =A0Post those
> > results. =A0Then we'll know how much margin you have to play with. =A0Fo=
r
> > example, right now I'm looking at -8.5dBmV downstream (a bit whimpy
> > but ok), 49.25dBmV upstream (pretty high... this is how much the cable
> > modem has to crank up the gain to get a signal to the head end), and
> > 34dB SNR (solid). =A0This trio is on the edge of reliability, in my
> > experience. =A0Ideally I'd like downstream a little higher, upstream a
> > little lower, and SNR the same or, heck, higher is always good for
> > SNR.
>
> That's an excellent idea. Thanks.
> Since this network cable is a serial - I can measure
> the signal from the external wall source to each connection
> point to determine if there is any radical loss of power.
>
> using the Webstar dPC2100 cable modem as a
> network diagonistic tool is an excellent idea
> thanks. The Webstar dpc2100 cable modem status
> on ip address 192.168.100.001 has a receive
> power and transmit power level. Because my old
> old 20db RF amplifier is a unidirectional I
> remove it for the following reading. Reading
> from the source signal down the line I found
> that by the time I get to third floor in the
> master bedroom I have a dramatic loss in my
> ablity to transmit a signal. I suppose I could
> redo this wall socket and see if that helps...
>
> here are my readings:
>
> 1) Original Comcast Cable Signal(RG6 cable via compressed Fconnector)
> Recieve Power =A0-05.2 dBmV
> Transmit Power +42.0 dBmV
>
> 2) Signal passes through Ideal 2Ghz 3-way digital/Satellite Splitter
> Recieve Power -02.2 dBmV
> Transmit Power 47.0 dBMv
>
> 3) Signal passes through Ideal 1Ghz 2-way splitter in Basement
> Receive Power -07.3 dBmV
> Transmit Power 52.0 dBMV
>
> 4) Signal passes through Ideal 1Ghz 2-way splitter to Living Room
> Cable TV outlet
> Recieve Power -13.5 dBmV
> Transmit Power 55.5 dBmV
>
> 5) Signal passes through Ideal 1Ghz 2-way splitter to Master Bedroom
> Cable TV Outlet
> Recieve Power =A0-17.7 dBmV
> Transmit Power 008.3 dBmv --- ouch!
>
> The last reading is really pathetic - given the drastic drop in
> signal =A0the office or guest room connection must be getting zilch.
>
> I was experimenting with those fancy twist on RG59
> f-connectors in the master bedroom... it looks like I am
> going to have to redo that wall socket as a crimp f-connector
> instead...
I found out that one of the twist on RG59 F-connectors had
gotten loose - tightening them up improved the cable signal.
I also check the cable serial connections before the wall outlet
in the master bedroom to see if any cable signal loss
could be due to any poor connection from the source signal.
I checked and retighten the basement splitter and replaced
a less expensive dollar store 1Ghz splitter (Trisonic) which
was being used byn the Living room cable outlet box with a more
expensive home depot store 1 Ghz splitter (Ideal) . After that
I was able to get an internet signal in the master bedroom.
The Cable modem signal in the master bedroom was
significantly improved at:
Master Bedroom Cable Internet Signal (Improved)
Received -14.0 dBmV
Transmit +58.5 dBmV
However, when I went to the next serial connection,
I was unable to get an internet cable signal. In the Office, the
next serial connection, though. Stripping off the wall outlet
and attaching the cable modem directly with the Ideal
1 Ghz splitter the cable modem signal was:
Office cable modem signal
Received -21.8 dBmV
Transmit +09.3 dBmV
Guestroom cable modem signal
Received -17.8 dBmV
Transmit +08.3 dBmv
Neither the office nor the Guestroom (which are at the end
of this serial cable wire) can get an internet broad band
signal albeit the cable TV carrier signal is still strong.
I've run out of time for this project and I will have to leave
any improvements/fixes/repairs to another date. I label
the wires for a future date and close every thing up.
However, experience has taught me that using the
pre-installed RG59 cable/antenna serial wiiring in older
home can be problematic. The connection I was able
to get using the crimping tools was not always
satisfactory and the twist on connectors were prone to
disconnecting. Knowing that - using compression
instead of crimp on/twist on f-connectors probably would
have yield better results. Cutting cable lengths inside
the cable outlet box too short makes it difficult to
attach and fit the cable splitter inside the cable
outlet box - allowing for longer cable lengths inside
the cable outlet box makes installation easier
to do. Cable modems rely on a high quality
carrier signal - which degrades with each splitter
/connection point. Using RG59 an unamplified
internet cable signal becomes unusable to a cable modem
after it passes through four high quality splitters.
There definitely is a limit to how many times
an internet cable signal go through a splitter.
Here in the Washington DC, you can't buy certain
cable installation items, e.g. cable terminators,
and other cable installation parts appear to be of
substandard quality, e.g. bi directional RF amplifiers.
Getting professional quality installation accessories
and parts from the internet appear to solution.
For those who answered my posting
I like to say thank you again for your advice
and input.
Walter
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