Cable drop amp question - 1 Port Amplifier + 4-way passive splitter vs 4 port Amp - AVS Forum
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Old 02-05-2009, 07:35 PM - Thread Starter
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Hello all.

Thank you in advance for your help.

I have been having terrible problems with my cable modem dropping its connection. When it drops, the modem thinks the cable isn’t plugged in. I’ve called the cable company techs and they can’t see the modem at all when this happens. Unplugging the modem and plugging it back in usually doesn’t help though unplugging the actual coax and then plugging it back in often does. It will usually reconnect in a matter of hours if nothing is done.

The problem started when I got my Avermedia Combo PC tuner card and installed a 4-way splitter to accommodate it.

This is what I have found out:

Cable wiring – The cable comes out of the drop box and goes to the roof where it is split once with a low quality splitter. One cable, the irrelevant one to this posting, goes to the second bedroom and the other relevant one winds around the roof and eventually into the wall where it comes out in the living room. The cable run is probably 75 – 125 feet from the drop box on the side of the house by the time it pokes through the living room wall. At this point, the living room cable is split via a Monster 2400mhz 4-way splitter where it is fed into a cable modem, HDTV, and two PC tuner ports.

It turns out that the dropped cable modem internet is probably due to the long cable run and 2-way + 4-way splitters in the path. Here are my cable modem measurements with the setup described:

Downstream:
Signal to Noise Ratio: 35.6 dB
Power Level: -10.4 dBmV

Upstream:
Power: 51.2 dBmV

Talking with the cable company, it seems that the appropriate Downstream Power Level should be between 0 and -10 and upstream should be between 40 and 50. A downstream of -10.4 is weaker than what it should be and Upstream of 51.2 is likewise not strong enough. This would explain why the problem was introduced with the introduction of the 4-way splitter. When using the same setup with the only difference being a 2-way splitter in the living room the readings were:

Downstream:
Signal to Noise Ratio: 36.4 dB
Power Level: -7.1 dBmV

Upstream:
Power: 47.4 dBmV

These readings are all within normal tolerances.

As a result of this, I rewired my cable. The drop box is on the exterior of the living room wall. I made a hole near the drop box directly into the living room.

The cable now runs as follows:

Drop box --> through the wall on a 10 foot cable --> High quality 2-Way 2400mhz splitter
|
2-Way splitter Output 1 --> Goes to Cable modem on 6 ft RG6
|
2-Way splitter Output 2 --> Goes to input on PCT 1 Port +15db Amplifier --> Monster 2400mhz 4-way splitter --> HDTV, 2 to PC tuner
|
4-Way splitter Output 4 --> Uses the old cable to the roof to connect to the second bedroom

With this new setup, everything has been running smoothly so far, though I have just installed it today so only time will tell. The cable modem is now only separated from the drop box by 10 feet of cable and one 2-way splitter as supposed to between 75 and 125 feet of cable, a 2-way splitter , and a 4-way splitter.

The new readings are

Downstream:
Signal to Noise Ratio: 37.1 dB
Power Level: 1.3 dBmV

Upstream:
Power: 42.7 dBmV

Here’s my question: When I originally purchased the PCT amplifier two days ago, I imagined it running the lengths of cable as it was previously setup (to the roof, splitter, long cable, living room, splitter). This is why I purchased the one port version. There was only one cable running to the roof. All the splitting was done up there.

It was only while I was impatiently waiting that I decided to drill the hole in the wall and came upon my newer, superior cable run setup.

I can still return the PCT amplifier. How much benefit would I get by returning the 1 port amplifier and purchasing the four port version instead?

Is there any difference between 1 Port Drop Amp --> 4-way splitter vs. 4
Port drop amp
?

Is there a loss because there is an extra cable involved in the 1 Port Drop Amp --> 4-way splitter setup?

Is it worth returning the 1 Port version for the 4-Port?

Thank you for all of your help.
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Old 02-05-2009, 08:41 PM
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Originally Posted by inayat View Post

Is it worth returning the 1 Port version for the 4-Port?

Thank you for all of your help.

No. A 4-output drop amp is merely a standard drop amp with a 4-way splitter on the output, all in the same housing. With a single output amp, you can alter the configuration as you may need. If you add an outlet or two, you simply change out the splitter for the one you need. With a 4-output amp, it's not quite that easy.

CIAO!

Ed N.
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Old 02-05-2009, 11:21 PM - Thread Starter
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Thanks, Ed.

That is the answer I was hoping to hear. A one port definitely seems more flexible for the reasons you mentioned. Also, I'm a renter; my next place might not be able to accommodate a 4 port drop in which case there would be a ton of wasted dB.
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Old 02-06-2009, 05:32 AM
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If your system is working fine just leave it alone, your numbers look great and just an FYI when you look at your cable modem power levels the lower the upstream level the better.
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Old 02-06-2009, 05:33 AM
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Greetings ....

Which cable amps are considered the best - especially those that allow return communication with a cable modem?

Thanx-A-Lot, Frank-0-Video
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Old 02-06-2009, 07:23 AM
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Quote:
Originally Posted by Frank-0-Video View Post

Greetings ....

Which cable amps are considered the best - especially those that allow return communication with a cable modem?

Thanx-A-Lot, Frank-0-Video

Amplifiers with specs such as the ones here. Settop boxes also utilize the return path.

Unless it's just not possible, you typically want to split a cable modem off before an amplifier.

CIAO!

Ed N.
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Old 02-06-2009, 08:38 PM
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Be careful with the 4 port amps for modems/mta's as they will boost your upstream past desirable levels causing dropouts.The 1 port wont boost your upstream, just levels.
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Old 02-07-2009, 08:01 AM
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Be careful with the 4 port amps for modems/mta's as they will boost your upstream past desirable levels causing dropouts.The 1 port wont boost your upstream, just levels.

I am confused about this statement will you explain?
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Old 02-07-2009, 03:04 PM
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Quote:
Originally Posted by RCbridge View Post

I am confused about this statement will you explain?

Apparently, the signal going upstream has no levels. But, that's only if a single output amp is used. If you use a 4-output amp, it has levels. Not sure about a 2 or an 8-output amp, though.

How much clearer do you want it to be???

CIAO!

Ed N.
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Old 02-08-2009, 07:12 PM
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It's all crystal now!!
LOL
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