Quick question: we're doing the trim out for a large property, which is to have approximately 25 coax outlets throughout the home. Each is home run to our patch panel. Only cable TV will be carried over the coax (standard and high-def).

I'm assuming daisy chaining high-quality passive splitters won't do the job, especially for HD. We've never done a distribution this large, so I'd like advice on how many RF amplifiers should be used.

We typically use Channel Vision products, and I was thinking of using a 1 in 8 out passive splitter, into their 1 in 1 out RF amp, into another 1 in 8 out passive splitter, etc. Would the one RF amp in the chain be enough?

I recently did a similar project with about 20 television locations. I used 4 Channel Plus DA-550HHR distribution amps.

The cable goes into the input on the first amp, which feeds seven TV locations. the eighth ouput of the amp goes to the input on the second amp, which feeds 7 additional TV's and the third amp.

[Link: channelplus.com]

It works great

Generally speaking, the best layout is to place the amp first in the signal path, and as close to the incoming feed as possible. This allows for minimizing noise amplification and best S/N ratio.

It's also good practice to only feed the outlets in use, and have no unterminated splitter legs, even if it calls for changing splitters and/or reconnecting feeds as TV's are added or moved.

At a minimum, terminate unused outlets with terminating plugs, which are coax plugs with 75-ohm resistors in them. This reduces ghosting and other signal abberations.

Things to remember:

Splitters attenuate signal.
A two way takes away 4 Db
a three way takes away 6 Db
a four way takes away 8 Db
a six way takes away 11 Db
an eight way takes away 12-13 Db

(these are rounded up numbers, by the way)

If you are feeding 24 jacks, consider placing the Channel Vision cvt38 first in line, and then out to a 4 way splitter. Cascade from there to 4 6 ways. Essentially, your splitter loss per port is going to be in the 19 Db neighborhood. Use the output gain adjustment on the channel vision and adjust until signal looks right.

Do terminate unused legs. Use good quality f fittings. Brush your teeth after every meal.

Thanks to both Larry and Ahem for the info - just what I was looking for.

keep in mind a few things - incoming signal. how hot is it? test it first

if incoming signal is high it will freak out the amp

the db drop is valid for the high frequencies - lower channels will drop less. if your only having a few digital boxes / with cable modem, try to connect them BEFORE the amp. it will then not interfere with the return path of the boxes//modem.

depending on incoming signal stegnth use a six way splitter and connect 4 digital boxes, the modem and then the amp for the other sets. this config always works but you really need to know the incoming. cable companies are always screwing with what they bring in. Ive seen everythin from -2db to +20. a big spread.

I was going to respond but not e-mail in the profile.

Alan

Are we enforcing this one??

Sounds like a large property. Are there some really long RF runs and some very short ones? If so, you might want to consider using an RF amplifier with a tilt compensation control. If all of the runs are kind of the same length within reason, and the distribution point is fairly central. you might consider using a coiple of amplifiers at the cable Dmark point. One would feed a 16 way splitter, the other an 8 way. Select the appropriate amplifers for each distribution leg. Keep in mind that many cable pay per view services require equipment that will allow two way communication of the signal.

. Are there some really

You should always check incoming signal. Its hard to solve a problem without fully knowing what the problem is. My local provider is fairly consistant with incoming stregnth. When I go to other systems, even ones owned by the same company the incoming is VERY different. comcast has brought me signal in at +20 on the high end and only +8 on the low. No tilt comp needed. No am needed either for an 8 way.

Hey, what coax signal testers are you guys using? I am familiar with the expensive Fluke and similar ones, but not a CI friendly one (in terms of price). I dont need it to be as advanced as the cable companies, just test the signal strength and maybe do a tone signal so I can trace out coax lines easily.

Thanks as always.

i just bought a $1500 unit by Sencore. I did however start with an old microsam I bought off ebay for $50. it tested 3 programable channels. It worked

how far from the street is the property? is it set back does the cable company have to build a plant extension? if they do bring the tap right up to the house and run multiple drops into the home.if not use an amp with two outputs scientific atlanta makes a good one. each leg will have a +11 gain off each leg put a two way to an 8 way. but make sure you also put a two way before one of the amps for the modem try to never amp the data line your tx levels will ramp way up into the high forties and low fifties. but with that many outlets i would try to have the cable company run at least two drops. good luck

One detail, though: most three-way splitters do not have three equal outputs, but have one output hotter than the other two. This is because they are actually two two-way splitters internally.
Internal splitter A has two outputs. One goes to internal splitter B, the other is an output that is about 4 dB down. Internal splitter B has two outputs, which are the other two outpus of the three-way, and these are about 8 dB down.

The theoretical lowering of level in a splitter is 3 dB; most are 3.5; 4 is safe for being sure you have enough level. By the way, the 3 dB is NOT loss, because when you take a signal and split it two ways, each output has half the power of the input, or is 3 dB below the input. If the outputs are 4 dB down, then there is an actual loss of 1 dB and a lowering of 3 dB....


You always want the amp to be as far upstream as possible because amps amplify noise (and add some) as well as amplifying signal, so the hotter the signal, the better the signal/noise at the output of the amp. The other caution, though, that others have mentioned, is that too hot a signal going into an amp can cause it to distort. This shows up as grungy signal as well as diagonal lines and other crap on channels which are multiple frequencies of the channels that are overloading the amp.


Rinse. Repeat.

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