can comcast put an amp near the pole instead of at the house? - AVS Forum
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post #1 of 43 Old 02-15-2013, 11:23 PM - Thread Starter
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I used my modem to test the signal strength at the end of my drop at the house, and it was like -2dBmV before my splitter. My house is like 210ft from the pole its tap is on. I can see it’s a 14dB value tap. The drop to my house is RG11, and I saw a chart showing that RG11 looses about 4-5dB/100ft. and that would be like a 10dB loss from the pole to the house. I hear the tap gives out about 10dB? An amp at my house wouldn’t be good because its already weak and somewhat noisy there. Can comcast put a 10-15dB amp on my drop at the pole?? So the signal is like 10dB after the 220 ft of RG11? Or can they only put an amp at the house? Please help. Idk if it matters but I live in md.
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post #2 of 43 Old 02-18-2013, 07:36 PM
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It's very unlikely that there is only 10dBmV at your tap. Most CATV systems nowadays design their systems to have a signal level of 15-20dBmV at the tap. Series 11 cable loses ~8dB over 220` @750MHz.

Keep in mind that the signal level that cable modem reads is the QAM level, which is 10dB lower than analog. That means that the analog level is ~8dBmV, which is just right.

Placing the drop amp at your youse would be just fine

CIAO!

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post #3 of 43 Old 02-18-2013, 07:51 PM - Thread Starter
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Isn't the QAM reading what matters? I have Digital Preferred TV and BLAST internet. When my modem reads around -25dBmV - -17dBmV is when it has issues, and the channels on my cable boxes that seem to be lower than most other channels and seem to go out first are operating at 609MHz. they start tiling around -16dBmv.

On an average day, my modem reads around -18dBmV (the avarage, because my ARRIS modem has 4 different downstreams on different frequencies), and my TV Boxes from -12 to -19 (different channels/frequencies)

i don't think anything else matters besides what the modem and boxes read.


Here is my setup now:



Drop>3way split

line 1 > to Settop1
line 2 > to 2-way splitter > then from the 2 way, one to settop 2, the other to my modem
line 3 > settop3


im pretty sure 3 of the 4 inside lines are RG59 and one is RG6, i plan on replacing them all soon because i did math and for the approx distance for each ill save from 3dB - 8dB on each line.

and im going to eliminate the 2 way splitter, and use a 4 way outside so each device has its own line of the main splitter.
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post #4 of 43 Old 02-18-2013, 08:41 PM
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Yes, it is the QAM level that matters. I was just illustrating that the signal levels at your house are fine.

Over 100 feet, there is less than 0.7dB of difference between RG6 and RG59 cable. If you are looking at 3-8dB of improvement by replacing the RG59 with RG6, you have some mighty long runs.

Place the drop amp right before the splitter, and you'll be fine. Actually, I would install a DC-6 with the TAP leg going to the cable modem, and the OUT leg going to the drop amp, which then goes to the 3-way splitter that feeds the TV outlets.

CIAO!

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post #5 of 43 Old 02-18-2013, 08:45 PM
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Are you actually experiencing a problem? If so, allow the cable company a chance to rectify it before you start adding amps and cutting new fittings.
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post #6 of 43 Old 02-18-2013, 08:48 PM - Thread Starter
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RG59 looses 13dB/100ft
RG6 looses 5dB/100ft

Obviously my signal at the House is NOT fine, or else my modem wouldnt be reading -2 with NO SPLITS, and NO other cable after the drop.

And i heard if your signal is weak (below 0) amping it there is a terrible idea. and it would ampify the noise

So if a tap lets out 15-20, and i have 210ft of RG11, and im getting -2 at the house, my drop may be bad. or maybe the tap is bad, because oddly enough, they are replacing my neighbors drop as we speak too o_0

The drops were installed in like 1992...
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post #7 of 43 Old 02-18-2013, 09:16 PM
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I don't know where you get your numbers from. at 750MHz, RG59 cable loses 6.97, while RG6 loses 5.65. I guess that is a difference of 1.32 isn't it? ;-)

That's 15-20dBmV analog, which is 5-10dBmV QAM. The F.C.C. says there can be no less than 0dBmV (analog) at the groundblock. That's -10dBmV QAM. You have -2 -- well above the minimum. If your cable modem reads -2 and you add the 8dB for the loss through the 220' of RG11, you get +6dBmV at the tap. Right where it should be.

CIAO!

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post #8 of 43 Old 02-18-2013, 09:25 PM - Thread Starter
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I got my numbers from many sources, here is one:


looks like you read that wrong, thats 16, not 6 wink.gif

Im not worried about analog, neither my cable boxes nor modem uses it, im talking digital

If its -2 at the house, a 4 way splitter takes 7.5, (now down to -9.5, and a few for distance), were at -15dBmV at the devices, out of comcasts' -10 to +10 dBmV recommendations, +/-15 is the out of spec point, and its right there....
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post #9 of 43 Old 02-18-2013, 09:49 PM
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I eventually found that chart as well. A manufacturer's chart can be found at http://www.tonercable.com/assets/files/TechnicalReference/Cable-Atten.pdf.

I only mentioned analog as a point of reference. So, let's talk strictly digital (QAM). That 0 you mentioned earlier (post #6) is analog as well. That becomes -10 (QAM).

The minimum signal level allowed at the groundblock is -10dBmV. You're at -2, which is well above the minimum allowed. You don't need more signal hitting your house. You may need more signal for distribution throughout your house, but that's a different point.

CIAO!

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post #10 of 43 Old 02-18-2013, 10:00 PM - Thread Starter
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I thought it had to be enough to efficiently supply enough signal for the average number of splits for a house (3-5), well with -10, you can do ANY splits w/o being out of spec?
And everywhere else i heard, the drop should have 10-16 at the house, with NO amps. that way it can be split like 4 times, and with distance, be at the targeted 0dBmV at your devices (settops, modems)
There was no talk ANYWHERE (ive been researching and planning this almost daily for like 5-6 months) of there being a analog reading to differ from anything else...

And why is your chart completely different from the many ive found?
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post #11 of 43 Old 02-18-2013, 10:16 PM
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F.C.C 76.605(a)(3) reads "The visual signal level, across a terminating impedance which correctly matches the internal impedance of the cable system as viewed from the subscriber terminal, shall not be less than 1 millivolt across an internal impedance of 75 ohms (0 dBmV). Additionally, as measured at the end of a 30 meter (100 foot) cable drop that is connected to the subscriber tap, it shall not be less than 1.41 millivolts across an internal impedance of 75 ohms (+3 dBmV)."

These rules were written when there was no such thing as digital cable TV. Analog was all there was. That's why it's important to note that QAM (digital) is run -10dBc (10dB below analog). The rule reads 0dBmV (analog), which equates to -10dBmV (QAM).

As you read in the 2nd sentence, it talks about the drop being 30 meters (or 100 feet). Your drop is more than double that. Doing the math, we find that there is a signal level of ~+6dBmV at the tap, which is within the 5-10dBmV that Comcast usually runs.

CIAO!

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post #12 of 43 Old 02-18-2013, 10:25 PM - Thread Starter
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Right, but for my 4 way split, and my target value of 0dbmv at my 4 devices, I need 10db at the house (-7.5 in splits) and some for distance. Everyone I've heard (including a step by step install by a real on duty cable tech on YouTube) said there should be about 10-16 db at the house (digital), that way there can be splits , and distance, and still have close to 0dbmv at the devices...

And my signal is too weak at the house to amp it there cleanly. My SNR would be too low...
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post #13 of 43 Old 02-18-2013, 11:12 PM
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The signal level hitting your house is well above the minimum required by the F.C.C. (referenced above), so I don't know where you get that it's too low. But, do whatever you want.

To simply answer your original question, no, Comcast won't put a drop amp on the pole.

CIAO!

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post #14 of 43 Old 02-18-2013, 11:20 PM - Thread Starter
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The FCC and what will cause issues apparently are worlds apart...
If its -2 coming in, then -7.5 in splits, and for distance, they're around -13, out of comcast +\-10 specs...
Comcast states that the targeted reading at devices is 0, how can you achieve that, if you have less than that on your drop? Before splits and distance of in home wiring?
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post #15 of 43 Old 02-19-2013, 06:53 AM
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The F.C.C. develops those rules in order to prevent issues, and they've been doing a pretty good job for decades.

As I wrote in post #9, you do need amplification for distribution throughout your house -- you just don't need it at the tap. Placing the drop amp at your house where the splitter is located will do you just fine.

When you connected your cable modem directly, without the splitter, you probably used a barrel connector to connect the 2 cables, right? Which means that -2dBmV you read at the cable modem was not the signal level at the house (splitter), but the signal level at the outlet. You need to either take the cable modem to where the splitter is and connect it directly to the drop that comes from the tap or calculate the cable loss from the splitter to the outlet to find out what the signal level is at the house (splitter) . If the distance from the splitter to the outlet is 25', the loss through the RG6 cable is ~1.4dB. That makes the signal level at the house (splitter) -0.6dBmV. Well within Comcast's spec of -10 to +10dBmV, and definitely well within the industry's specs of -15 to +15dBmV.

Drop amp specs call for an input level of ~0dBmV (+/- a couple of dB). You can't get much closer than what you currently have.

CIAO!

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post #16 of 43 Old 02-19-2013, 06:33 PM - Thread Starter
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I didn't use a barrell connector, I pluged the rg11 drop right into the modem.
I just figured they should provide at least 8db at the house, so you can do 4 or so splits and not need to worry about an amp, that's how most houses are...

But I tried putting a barrel on and running the drop, to the outlet my modem was on today also, my modem read -8dbmv, so it lost 6 from the drop, to that outlet...

And the +/-10 is what it should be at your modem and cable boxes, NOT at the house BEFORE splits.
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post #17 of 43 Old 02-19-2013, 07:33 PM
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Alright on the barrel connector.

Most houses are not 200+ feet from the tap, either. Cable systems are designed to have "X" amount of signal at the tap, usually 5-10dBmV, which according to the math based on information you have provided, your cable system is doing. The signal level at your tap is 6dBmV. They ran you a drop utilizing Series 11 cable -- most houses have Series 6 cable for their drop. The signal level at your house is well above the minimum they are required to provide. They have done just about all they can do to provide you with good service. Now, especially at more than 200' away, it's up to you.

CIAO!

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post #18 of 43 Old 02-19-2013, 07:49 PM
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So did you go talk to the crew/person replacing the drop? Let them know you have issues also. It doesn't get you anywhere having a peeing contest. RG-11. Seen many bad fittings that when replaced, drop was fine. Could be a bad tap. Have you contacted your provider?
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post #19 of 43 Old 02-19-2013, 09:28 PM - Thread Starter
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Well if your saying i can amp a -2dbmv qam signal, where can i buy a good amp? one with 1 output, and with the power adapter that uses coax for power, like this - http://www.amazon.com/gp/offer-listing/B000066E6Y/ref=dp_olp_0?ie=UTF8&condition=all

I do not buy online.

If i can talk to a comcast tech, could let me have one out of his truck for free?
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post #20 of 43 Old 02-20-2013, 06:07 AM
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Those amps are usually available at places like Best Buy (in the computer department).
If the Cable Guy thinks it will help, he'll often provide one...best to ask in advance, though. That way, he can have one on the truck, and not have to make a second truck roll.

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post #21 of 43 Old 02-20-2013, 06:43 AM
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He just may. More than once, I've heard of that happening - mostly with splitters, connectors and cable, but he may do a drop amp for you.

Not buying online limits availability quite a bit, and I don't know your area. I really hate suggesting Wally World, but if you do have one nearby, they sell one made by Winegard that has pretty decent specs. Actually, they have 2 models by the same manufacturer. One is a standard 15dB gain drop amp with a passive reverse (loses 2dB on the return path), while the other is adjustable on the forward gain up to 24dB and has 12dB gain on the reverse. I don't think you'd need 24dB gain on the forward path, but as for the reverse, you'd need to look at your cable modem to determine if it might be beneficial. In your cable modem (preferably at the outlet, after the 4-way splitter), look at the upstream power level. If it's in the 40s or below, you're perfectly fine without amplification. If it's in the 50s, it's approaching the threshold. Maximum is +55dBmV.

Here is a spec sheet for those amps: http://winegard.com/kbase/upload/wc-819.pdf. Keep in mind that when it talks about input and output signal levels, those numbers are analog. QAM is 10dB below analog.

Best Buy sells a 4-output drop amp that is their own, but there are no published specs.

CIAO!

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post #22 of 43 Old 02-20-2013, 02:43 PM - Thread Starter
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Just wondering, my cable box has 3 readings, QAM, fdc, and rdc, is fdc the analog reading?
The channel I'm tuned to is 621.000 MHz and its reading -14dbmv right now
The fdc is tuned to 75.250mhz at -7dbmv
Rdc is tuned to 17.000 MHz at 32dmbv
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post #23 of 43 Old 02-20-2013, 03:41 PM
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FDC is the downstream D.O.C.S.I.S. channel, and RDC is the upstream D.O.C.S.I.S. channel (where your cable modem talks). If you pull up your cable modem, you should see numbers pretty close to those. The -14dBmV, of course, is the power level of the channel to which your cable box is tuned.

So, it looks like you don't have to worry about return path amplification. wink.gif

CIAO!

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post #24 of 43 Old 02-21-2013, 02:35 PM - Thread Starter
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My modem upstreams are around 45dbmv
my modem downstreams are around -18 or -19 dbmv

and that fdc on my cable box is at -7dbmv at 75.000mhz, my modem downstreams are at 561.000, 543.000, 555.000, and 579.000 Mhz, all around -19dbmv... how can that be where my modem downstream talks?
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post #25 of 43 Old 02-21-2013, 03:56 PM
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From another forum:

"the rdc and fdc level on SA boxes are similar to docsis levels and ideal ranges.

fdc should be -10 to 0
rdc should be -50 to -35

or around that. rdc over -55 means the box is having a tough time transmitting back to headend which would result in vod problems."

The key word is similar.

It looks like your rdc may be a tad low. That may be corrected with an amp.

CIAO!

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post #26 of 43 Old 02-24-2013, 07:24 AM
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That is interesting that with such low D/S power that the U/S numbers are so low.
You would think that with so much loss on the down stream path that the upstream would be really high to overcome the attenuation!!
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post #27 of 43 Old 02-24-2013, 11:51 AM
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Quote:
Originally Posted by RCbridge View Post

That is interesting that with such low D/S power that the U/S numbers are so low.
You would think that with so much loss on the down stream path that the upstream would be really high to overcome the attenuation!!
Much of his loss is cable loss which will be much lower at low (return channel) frequencies. I've got about 100 feet of RG-6 and 13dB of couplers between me and the pole and my send level is 45dB. The modem forward levels are all around -10dB. I'm connected to an 8-way 11dB EOL tap. The OP could be on a 7dB or 4dB tap.
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post #28 of 43 Old 02-24-2013, 12:23 PM
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He wrote that he's on a 14dB tap. Over 220' of cable, I could see there being that much tilt.

CIAO!

Ed N.
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post #29 of 43 Old 02-24-2013, 01:40 PM
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Quote:
He wrote that he's on a 14dB tap
I see that. Forgot to re-read the OP before posting. Still, 45 dB send is fine.
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post #30 of 43 Old 02-24-2013, 02:12 PM
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Quote:
Originally Posted by egnlsn View Post

He wrote that he's on a 14dB tap. Over 220' of cable, I could see there being that much tilt.

Return should be 18-20 over tap value, forward levels would wind being flat out of the tap in a normal system.

All Comments made are my own and not of my employer.
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