Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?

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I currently have cable broadband internet from Comcast. The initial
basic installation was just a wire through the main exterior wall.  I
am leasing a Scientific Atlantic DPC2100 cable modem  from Comcast ( I
am getting about 4Mbps download/ 380 kbps upload currently).

My three floor townhome was built prewired for cable/TV antenna - but
the tv antenna/cable wall jacks were not installed. Recently, I
decided to use the pre existing internal (wall) wiring so I could set
up my  computer upstairs with cable broad band internet connection on
the third floor. So I installed five tv antenna/cable wall sockets/
jacks. I  found out that the house was serially prewired with RG59
dual shielded coaxial wire and that I had to use a 1Ghz two-way
splitter to connect each wall jack. Initially I was able to get an
excellent cable and internet signal from the first(ground/basement)
and second(main)  floor wall jack; however, the third(top) floor wall
cable jacks had very poor cable signal and no internet signal. The
cable signal had apparently degraded signficantly as the length of the
wire increased and the number of splitters increased.   By installing
a Radio Shack RF amp (VCR/TV/FM Variable 20db amp  Catalog No 15-1113)
at the very front of this serial RG59 cable - I was able to boost the
cable signal so that all the cable channels were strong enough to view
clearly on the third floor but it completely blocked the cable
internet signal on every floor. I know that the signal loss is due to
the use of serial prewiring of RG59 and that it would have been better
had the house had prewired with parallel RG6 cables ; but I would like
to avoid ripping up the drywall and rewiring the house from the ground
up.

Is there a RF amp/splitter ( F-connector) that could  boost both the
cable and internet signals?

Walter

Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?
On Sun, 20 Jan 2008 07:20:25 -0800 (PST), drydem

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Serial wiring? Ouch, what a mess of a bad idea. As you know, the best
thing would be to rewire the entire house with 'home run' cables,
preferably quad shield RG-6 or equivalent rather than RG-59. That's a
lot of work, though.

Barring that, I would add a 2-way splitter where the cable arrives at
the house. One output of the new splitter would connect back into the
house wiring and would power all of the existing TV jacks, and the
other output of the new splitter would connect to a new cable that
would run up the outside of the house to the new office. With this
plan, your new office would have two cable jacks, one for TV and one
for Internet/TV. If necessary, you could still add an RF amp to the
non-Internet side of the new splitter without significantly affecting
the cable modem.

--
Bill

Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?
Bill M. wrote:
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I agree with everything except the running of the cable outside.  That
would have to be a last resort.  If at all possible, try to find a way
to run it inside if that's what you end up doing.

Another alternative would be to put a decent wireless router at the entry
point and going wireless to the third floor for your internet access.
That would eliminate the need for tearing up your walls or hanging wire
outside the house.


Oftentimes, you can replace parts of your run by just tying one (or even
two cables) to the end of your existing cable and pulling the new cable
through, but that can easily be defeated by staples and such that may
have been used.  You could test that easily enough by just tying some
string to the end of the cable and seeing what happens if you give a bit
of a tug on the next outlet in line and see if the cable runs free.

That would allow you to at least run parallel cables along the serial
route which wouldn't be as short as home runs could be, but the RG6
would make up for the loss due to length over the RG59.

I would think any RG6 or RG11 should be great for longer runs of
non-baseband cable (dual or quad shielded only if you can afford it),
but a CM rated RG59 will handle most of your *short* haul needs with
not much less dB loss than RG6 (in your case with them all strung
together serially, that probably isn't true).

Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?
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yes.

I thought about that - but I decided
against doing that because of the way the RG59
cable is threaded. The RG59 cable is threaded
from the roof/attic and winds through three
bedrooms (third floor) to the living room ( second
floor) and then drops down into an unfinished
basement(first/ground floor). The attic cable
was put there by the builder to accommodate
an attic TV aerial antenna since a rooftop TV
aerial antennas are banned by the HOA.
Rethreading  the cable is also best done as a
two person job ( one feeding cable, one pulling
the cable).  Given the limited time I have allocated
for this project - I decided that rethreading would
be best for a later project.


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Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?
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As others have said, the best thing would be to run a separate cable for
the modem, but you might be able to get away with your current setup by
using directional taps instead of simple splitters.  A splitter sends
half the incomming signal to each outlet, so the first jack in the chain
gets 1/2 the original signal and sends 1/2 along the chain, the next
jack in line gets 1/4 of the original signal, the jack after that 1/8,
then 1/16, etc.  Taps, while harder to find, split the signal unevenly
so that most of the signal is sent along the chain with only a small
amount being sent to the jack, which keeps the signal level from
diminishing so quickly as you go along the chain.

If you still need an amplifier, you must get one that has a return path
(bidirectional).  Simple unidirectional amplifiers block the cable
modem's upstream transmissions, which keeps it from working.

-Larry Jones

I think we need to change the rules. -- Calvin

Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?

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There are a few possibilities.  You're (admittedly) using the wrong
cable, you're crimping your own connections, using a Radio Shack
amplifier and a Home Depot 3-way splitter.  It's amazing you get TV
much less cable modem signal.  :-)

May I suggest a more methodical approach?

Let's start by plugging the cable modem in where it last worked.  Look
at the web page at http://192.168.100.1 where most DOCSIS modems will
have a signal page somewhere... and record upstream power level,
downstream power level, and signal/noise ratio (SNR).  Post those
results.  Then we'll know how much margin you have to play with.  For
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).  This trio is on the edge of reliability, in my
experience.  Ideally I'd like downstream a little higher, upstream a
little lower, and SNR the same or, heck, higher is always good for
SNR.

Next, add in the 3 way splitter without moving the cable modem from
that physical location.  Load the 3 way splitter with 2 legs hooked to
something that terminates the line so we dont' worry about reflections
and such, and repeat the test with the cable modem hooked into the 3
way splitter right there in front of you.  This eliminates wiring
losses and sees if the splitter itself is garbage (which it may be
given its purchase at a building supply store).  Visit that diagnostic
web server in your cable modem again, record those power levels and
SNR and post here.

Now move the cable modem down to the end of the line.  If the modem
will give you any signal levels there despite its inability to sync,
record those.  This will help narrow doewn where the problem is.

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That's good-there's no amplifier between your cable modem and the head
end.   But you can do better.

You'd probably get nearly a 6dB improvement if you throw away that
3-way digital splitter, and replace it with 2 items:

        a directional coupler.  A very high quality one is
                Antronix CMCDT2109T  but I've also seen CMCDT2106T.
        a 2-way splitter rated for sufficient bandwidth. Antronix
                CMC3000H  OR equiv.

You won't find these at radio shack, but I bet your cable company has
em.

House feed comes into the directional coupler, through output goes to
cable modem, tap leg goes to 2-way splitter which then feeds your main
floor tv, and that whole mess of serially connected stuff
respectively.

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Don't try to swing for the fences just yet.  Build up the distribution
system slowly and test the cable modem and gather data at each step of
the way.    You've got a rather complicated setup, and cable modems
are finicky.  

Best REgards,
--
Todd H.
http://www.toddh.net /

Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?
On Jan 22, 12:17=A0pm, comph...@toddh.net (Todd H.) wrote:
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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  -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  -17.7 dBmV
Transmit Power 008.3 dBmv --- ouch!


The last reading is really pathetic - give to drastic drop in
signal  the 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...



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Yes.
Radio Shack and Home Depot have only the basics.
If my cable company has them they aren't selling them to DIYers like
me
=2E

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Thanks for all the help!

Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?

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This reading doesn't make sense.  It's 3dB higher than the original.
Which leaves us wondering how we got 3dB of gain by going through a
3-way splitter.  Something is wonky.

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Yer on the edge of the cable modem working without packet loss at this
point.

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And transmit is probably maxed out at this point.   Cable modem
probably wont' sync here.

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Transmit opwer obviously something strange here.  but with 55 being
the max most modems will try to push, weird readings here don't pahse
me On the receive end, which is all you care about because it's a TV
line for ya, you're seeing the same 6dB drop you've seen after prior
2-way splitters.  3.5dB is the nominal insertion loss of a 2-way
splitter, but the cable modem may be testing at a relatively high
ferquency that sees more loss than nominal.  Cable losses also
contribute and are frequency dependent.


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Nah, it's not really that bad.  Does the TV work there?  Of course the
modem work as it's out of the upstream gain range.

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The twist on's yeah... I seemt o recall them being a trouble spot.  


--
Todd H.
http://www.toddh.net /

Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?
drydem wrote:
 >
 > Yes.
 > Radio Shack and Home Depot have only the basics.
 > If my cable company has them they aren't selling them to DIYers like
 > me
 > .

When I added internet to my cable, they came out and added a grounding
block, grounded it to my AC distro panel, put new terminators on my
RG59 home runs and installed a new 1:4 splitter.  I asked them for a
75-100' cable so I could later run it myself through the ceiling to my
cable modem and they whipped up a cable, tested it and handed it to me.

They'll pretty much give you whatever you need if you ask nice has been
my experience.

Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?

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Agreed.    

Since cable companies don't really know how to respond to change
requests for existing customers, one tack for Drydem to take is to
move the cable modem to an outlet where it doesn't work, then call in
a service request indicating it's not working to the point they send a
technician out, and they'll get you squared away generally, applying
DC's appropriately as needed.

Dunno how many if any cable companies actually track where in your
home they installed the modem.  The tech onsite will see that you made
your own ends perhaps, and that the cable might be wrong, but they
also might assume that the original installer didn't want to deal with
running new cable and that the homeowner might not have had anything
to do with it.  Applying the right level of "I'm not sure what's going
on, but I'm hoping you can help make it work" along with being affable
generally gets you in a better place by the time the tech leaves.

"I moved my office, and needed the cable modem in this room, and
thought it was like DSL at my other office where I could just move the
the box to any other jack in the house."  

the cable company won't want to make too big a deal of how cable modem
technology is more finicky than DSL, and they'll most likely do what
they can to make it work where you want your modem.  They'll install
quality directional couplers and splitters and remake ends with high
quality crimp connections until it works, generally.  

One thing to watch out for and not underestimate:  tight cable bends.
I had a tight 90 degree cable bend back in a wall jack that turned out
to be the culprit of 9 friggin dB of signal loss.  I couldn't believe
it myself.  STraighted it out, redid the end and voila.

--
Todd H.
http://www.toddh.net /

Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?
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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

Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?

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And now you know why twist ons are generally considered garbage.   :-)

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LOL.  Splitter from the dollar store.  Alrighty.  :-)

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At +58, you might get the modem to sync, but I bet packetloss is
horrid.  I'm impressed the internet even worked there.  Kudos to that
cable modem.

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No surprise based on the prior hop's numbers.

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Those transmit numbers appear to be bad data if the modem wasn't
syncing, by the way.


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Yup, it's why teh cable company uses em.

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Absolutely.



Yup.


Sounds like you learned lot.

Now that you're out of time,  can you indicate why you're so hesitant
to enlist your cable company's help with this in the form of a repair
call?   Unless they have some sort of policy that says they're going
to charge you for inside wire work (which over 3 cable providers I've
not personally seen), what's to lose?  

--
Todd H.
http://www.toddh.net /

Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?
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Agreed. Even if they charge you for the trip, it likely won't be more
than $50 or so, and that will include any parts used and replaced
fittings. It sounds like you have several hours tied up in this
already, and lots of trips to Radio Shack.


Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?
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You're never going to make this work without replacing all the splitters
at the outlets with directional taps -- there's just too much signal loss.

-Larry Jones

See, it all makes sense.  See?  See??  They never see. -- Calvin

Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RFamp recommendations?

drydem;2154627 Wrote:
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Get the house rewired with rg-6 cable. the rg6 will give you a better
signal, picture, and supports digital tvs with hdtv. also rg6 also
supports faster transfers of signals from the feeder, to the house.


--
leroymcqy
http://forums.speedguide.net


Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?

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Because you failed to use an amplifier with a passive return.


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You don't want an amplifier involved with the cable modem at all unles
syour architecture absolutely requires it.   The right way to do it is
to call comcast and have them  do this work properly for you.  If you
dont' want to pay what they might charge an existing customer,  you
might consider cancelling for a few months and signing up again and
gettin the cable modem location and number of activated outlets you
seek in the new customer work order, and it'll probably be free, and
it'll be their problem getting a good cable signal to your cable
modem.

However, I can share what I've learned over 12 years of having a cable
modem.  

You'll want to use a directional coupler instead of a splitter in
front of your cable modem, and feed the cable modem the low-loss
output of the directional coupler.  A DC differs from a splitter in
that the loss on each leg is asymetrical.  It has essentially a
"through" leg that has minimal signal loss (1dB or less) in either
direction and a high-loss "tap" leg that has 6dB loss.

After the DC, on the high loss output, put a quality amplifier, and
then do all your splits for your TV's.    The low-loss output of the
DC goes to the cable modem.  That way your cable modem gets strong
downstream signal and doesn't have anything difficult to push upstream
signal through.  

If you absolutely must have an amplifier in-line with the split that
heads to the cable modem, it must be an amplifier compatible with
cable modems.  Specifically it must be truly bidirectional in
operation, or more typically simply have a passive return path whereby
the upstream cable modem communication can actually pass without
serious degradation.  These amplifiers are somewhat expensive.  I have
2 in my house provided by the cable company though.  The problem with
amplifiers is that they add noise, and cable modems for downstream
data are more sensitive to noise than they are low signal strength.


If you play your cards right,  you can make all this your cable
company's problem.

You may find it far easier, however to keep your cable modem where it
currently works and run either cat5 or 802.11 wireless networking to
your computers.  With access points that can be configured as wireless
clients now costing $40-$60, it becomes hard to justify too many
directional couplers, or even a single bidirectional amplifier.

Best Regards,
--
Todd H.
http://www.toddh.net /

Re: Cable Broadband Internet Signal loss from serial RG59 cabling - RF amp recommendations?
On Jan 20, 10:06=A0pm, comph...@toddh.net (Todd H.) wrote:
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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.  I replaced
the older RF 20db Amplifer with the newer Bi Directional
RF 10db Amplifier - while the cable channel signals were still
usable/powerful --  the cable modem was still unable to
get an internet broadband signal in the office.  Why didn't
it work? I'm not sure.


Currently I have the source cable line (from the exterior wall)
connected to a 2Ghz 3 way digital splitter (Ideal from Home
Depot). The Main Splitter output line #1 goes to the cable modem
( for this computer I am using now), the Main Splitter output line#2
goes to a cable ready TV (main floor)  which I am using to
monitor the initial cable signal, the Main Splitter output
line#3 goes to the RF amplifier which power the rest of
the cable wall jacks via the serial RG59 cable. Behind this
RF amp there are five 1Ghz two way splitters(Ideal) that
are connected serially from closest to farthest away:
Splitter#1:Basement Fconnector, Splitter#2:LivingRoomWallOutlet,
Splitter#3: MasterbedroomWallOutlet, Splitter#4: OfficeWallOutlet,
Splitter#5: GuestroomWallOutlet. From the guest room, the
cable goes up into the attic where part of it is stapled to one
of the rafters (so you can find it). I am using a DataShark
TV-Cable crimping toolkit to make the connections.



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Thanks for your input.

Since the house to already pre-wired - I was hoping that with a little
bit
of effort I could gain access to my cable broadband upstairs.

I have wireless equipment but I wanted the faster network access that
               the cable modem allowed.

Connecting a cable modem to an Giga or Fast Ethernet router in the
basement
and then rewiring my home with parallel Cat6 lines would offer
signficantly
higher data transmission benefits for about the same effort  as
rewiring the
house with parallel RG6 lines. The biggest effort for such a future
project
would be tearing up and then repairing the drywall.



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