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

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.

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).

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

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,

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

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.

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.

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.

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.

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.

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,

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...

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

Thanks for all the help!

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.

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

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

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.

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.

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

drydem wrote: >

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.

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.

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

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

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

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.

No surprise based on the prior hop's numbers.

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

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

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?

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

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.

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.