Buying too many devices and loosing signal

[QueOnda]

Anyone know of a good resources on how to best setup my tv signal?

I've read other people having the same issue in the other forums and it's more of a try this then try this.

Well, instead of buying an over $1000 meter. The HDHR and the cable modem, I can measure the SNR DB. I wonder if my PVR500 can (i doubt it). I think my concast box can (or can it). I've also seen different splitters having different ratio (gains). So if you further down the pipe you can use a different ratio to minimize your signal loss.

I worked for a company just for the summer and they installed video services to hotels. Of course I don't remember, cuz I was with them a short time but I was going with the tech and trying to find the back splitters. (there are splitters all over the place). Had to find the back splitter and replace it with one with would give you the least lose. I need to understand that aspect and might help people with similar issues.

Another thing, concast, I believe they may have the signal weakend in the 1st place to just power several tvs. If you doing anymore you just making the signal tooooooooooo weak.

I have a main box with has the main concast signal coming in:

4 way: HDHR, modem, free out to another 8 way splitter to go all over the house.

On leg, I have 2 pvr500 and want to connect a cable box. On another leg, I want to connect another hdhr. on another leg, I have a tv and another leg a tv. of course have other free legs.

HELP!!!

[Brent]

Queonda,
One other person you might want to ask this question of is Rich on the SS forums. He's very knowledgeable about this sort of thing. I'm sure others will chime in here as well though.

[paulbeers]

Originally Posted by QueOnda

Anyone know of a good resources on how to best setup my tv signal?



HELP!!!

Well you have your signal coming into the house on a 4 leg splitter, then to an 8 leg splitter....this is going to be doing about 21db loss in signal/power (7db loss on the 4 way and then an 14db loss on the 8 leg if they are good splitters) on anything off of the 8 way splitter, which on the logrithmic scale means that you have now lost almost 99% of your signal/power!!

Now also factor in that the PVR500's have an internal splitter....that means that you are losing even more signal/power loss on those two tuners.

Here's a good website to check out (fairly technical though):
http://www.siemon.com/us/white_paper...atis-inadb.asp

While there isn't necessarily a magic device on how to fix your signal problems, I can pretty much tell you that if you aren't amplifing your signal before even your 4 way split with a decent (not radio shack or other disount amplifiers), you are never going to get a good result. Make sure you also get an amplifier that lets you return a signal otherwise your cable modem will not work (or you can do a 2 way split directly into the house one to the cable modem and one to any "tuners" if that makes sense).

I hope this helps.

P.S. On a completely unrelated topic, this is my 1000th post...Yea me!

[davin]

http://www.cabletvamps.com/Products/EDA-FT08100.htm

[MeInMaui]

Originally Posted by davin

http://www.cabletvamps.com/Products/EDA-FT08100.htm

+1

I added this to my system and it is working great. The key is to minimize the number of splits. In my case, I have the above linked amp hooked up to a cable connection in the garage (all of my cable runs go directly back to the outside cable box). I then have all of my tuners and my cable modem connected to the outputs of the amp. This was the configuration that gave me the least total number of non-amplified splits and maintains the strongest signal at all of my tuners.

Aloha,
Mike

[Conejo]

A lot of people are using signal splitters where they should be using taps, to prevent uneven distribution of signal levels.

[begin Plagiarized text]

PRIMER: poorly written to confuse you further

To receive a TV signal it has to be detectable (have a signal level) and that signal has to be above all other undesirable background noise (signal-to-noise ratio).

Signal level is measured in dBmV (decibel-milivolt)
The dBmV is a voltage value relative to a reference – in this case 0 dBmV (1 miliVolt). The reference level was defined in the late 1950s and references the minimum voltage required by a television tuner to produce an excellent television picture.

The important thing to note here is the number.

You start out with a number. For every splitter or tap you subtract its loss value from this number. You WANT to arrive as close to ZERO when you reach each device.

1. Your Cable Co should deliver a 15 dBmV signal at the cable tap an the pole or street (standard)

2. Every 100ft of RG-6 Cable will incur a loss of -2 dBmV to -6 dBmV (dependent on frequency).

3. The use of TAPS or SPLITTERS will reduce your usable signal along the way, both from being tapped or split and from insertion loss. A two-way hybrid splitter has a -3.5 dBmV loss per leg. A regular 4-way splitter has -7 dBmV loss thru each leg.

4. Adding an Amplifier can increase your usable signal along the path (as long as the input signal is still above the background noise level), In-line amps can provide +10 dB to +25 dB signal gain.

5. Knowing the loss or gain levels of your cabling and connectors you can simply add the numbers together to see if your end-point signal is HOT (too high), nominal or low.

- The 'perfect' signal level that a TV or cable box likes to use is 0 dBmV at the input.

- Most analog TV sets can give a clear picture on signal levels between -5 dBmV and +5 dBmV.

- Digital television tuners operate with a lower minimum required voltage or about -12 dBmV. You will note this is 12 dB below the reference level of 0 dBmV for analog TV. New digital television tuners can accept a signal level between -12 dBmV and 16 dBmV.

- Cable Modems like to be at the beginning of a run, at the first split. Specs say they operate well on a signal level between -15 dBmV and +15 dBmV downstream, but generally don't work well below -10 dBmV.

- Upstream devices like Cable Modems and Set-Top-Boxes also send signals UPSTREAM back through the cable system. Placing an STB too far down a line of splitters can prevent it from sending signals that let it work with Video-On-Demand (VOD) requests.

Amplifier: Pumps up the signal level (both noise relative to signal)
Two-way Amplifier: An amplifier that allows two-way communication for Modems and PPV/VOD STBs
Splitter: A passive device for equally dividing an input signal level to several output ports.
Tap: A passive device for delivering a portion of the signal level to output connector(s) while allowing the majority of the signal level to continue along the distribution path.
PAD: An in-line device for lowing the signal level when it's too hot (high) for a device.

dB's are commonly used to express the ratio in terms of VOLTAGE or POWER. What is important here for video signal levels is the POWER ratio. A -3dB loss means that the output is ONE HALF of the input. And a -6 dB loss means the output is ONE FOURTH of the input. And a -10 dB loss means that the output is ONE TENTH of the input. And a -20 dB loss means that the output is ONE HUNDREDTH of the input. Seemingly small dB losses are really LARGE signal losses!!

[/end Plagiarized text]


But, generally speaking, you WANT to arrive at between -5 dBmV to +5 dBmV at the end of the cable when connecting to each device, with 0 dBmV being a perfect target.

[Menehune]

First thing I would suggest is immediately place a good amplifier before your first splitter. You want to boost the signal to overcome the losses in the splitter and have a signal with a decent signal level coming out of the splitter. Do not place the amp after the splitter since you will be amplifing the noise coming out of the splitter.

I also recommend you check your connectors and if you have any screw on type, replace them with good crimp connectors. I like snap-n-seal compression fittings, I use them at work in my buildings. I have seen screw on fittings fall off when I touched the cable.

If you know you are going to have a long run of cable or a large number of rooms splitting off the cable, I recommend you install taps instead of splitters. Send the "out" to the next room and preserve as much of the signal level as possible without using an amplifier.

Oh and don't use RG59 cable. Save yourself the headache (and high signal loss) and use at least RG6.

[Fuzzy]

With your current setup of a 4-way then an 8 way, it is harder to get great results. The problem being, if you put an amp before the 4-way, then the signal after the 4-way's will end up too strong. It is best to have the same drop everywhere, and adjust the input so that they are all at an acceptable level.

You also probably have the signal attenuated at the street, which comcast should be able to turn up if you need it. The best 'quick fix' would actually be to put a +14db amp on the input to the 8-way.

Illustration:


Something to keep in mind, that too strong of a signal can be JUST as bad as too weak. This is WHY Comcast has attenuators at the street.

[stanger89]

A couple things, first, you're best off not cascading splitters, as you end up with each output having a different signal level. Say you need 4 outputs, you can either use 3 2-way (-3.5dB) splitters or 1 4-way (-7dB) splitter.

To connect the 2-ways, you cascade the 2-way splitters , connecting one output of each splitter into another splitter. If you do that you end up with one feed thats -3.5dB from the source, one that's -7dB, and two that are -11.5dB (losses add).

Comparatively if you use a single 4-way, all 4 outputs would have the same -7dB, signal, worse for that one TV, but better (or equal) for the other three.

Or maybe a better way to say it, is you shouldn't "unevenly" cascade spitters, if you're going to cascade them, make sure the path to all outputs is the same.

Now, regarding that picture, arguably, the second way is actually the better way to go. You want to amplify the signal at the point of best SNR, otherwise you're just amplifying noise, and that doesn't do you any good. The exception would be if that amplification would either be at a point where the amp would clip, or where it would overload your recievers.

But in reality, either one of those options is bad, if you need 11 outputs, you'd probably be better with (if you can't find and 11-12 output distribution amp) an amp followed by a 3-way splitter (which would be -5dB) feading 3, 4-way splitters (-7dB). Your total worst loss would only be about -12dB and all outputs would be the same.

[Fuzzy]

I made that pic based on the assumption that his current splitting arangement is pretty much set based on his current cable runs (as is the case in most homes). The 2nd drawing would, indeed be better, if you added attenuation on the output of the 4-way splitter to knock that signal back down to a lower level. But as I said, I was demonstrating the quick-and/dirty method of getting it all working. Most times an amplifier before the 1st splitter can be problematic, as it is usually outside the house, without a good source of power.

Granted, most my work in this has been done on large analog distribution systems, where too high of a signal is VERY problematic, which is why I try to always keep everything even.

[stanger89]

Originally Posted by Fuzzy

Granted, most my work in this has been done on large analog distribution systems, where too high of a signal is VERY problematic, which is why I try to always keep everything even.

Yeah, even is the key

[QueOnda]

Great discussion. Learning lots.

I did order the amp which davin and MeInMaui suggested.

I did get a 4 port from radioshack to try out (and to get me by) until I receive my order. Then I shall return to <them>.

Originally Posted by Conejo

But, generally speaking, you WANT to arrive at between -5 dBmV to +5 dBmV at the end of the cable when connecting to each device, with 0 dBmV being a perfect target.

Originally Posted by stanger89

Yeah, even is the key

Got ya. When I get this installed I'll see what the cable box, 2 hdhrs and cable modem tells me. I hope gives me useful info. Can I measure the signal on the PVR500? Probably not. Doesn't matter since in just analog.

Another thing to note based on my experiences, Splitters DO fail or start to fail. I had that issue from time to time.

The HDHR gives me Signal Strength, Signal Quality, and Symbol Quality in %. I know if you go below you go Red but what percentages do you actually want to make sure you don't over do it?

[Opus4]

Originally Posted by QueOnda

I did get a 4 port from radioshack to try out (and to get me by) until I receive my order. Then I shall return to <them>.

I've said this before & I'll post it again: if you want your local stores to stay in business, buying things to use temporarily & then return them when your internet-ordered item arrives isn't a very nice way to abuse local stores.

And, I've edited out your insulting name of the store.

- Andy

[QueOnda]

Originally Posted by Opus4

I've said this before & I'll post it again: if you want your local stores to stay in business, buying things to use temporarily & then return them when your internet-ordered item arrives isn't a very nice way to abuse local stores.

And, I've edited out your insulting name of the store.

- Andy

Sorry for my manners, I won't do it again. I do give them a lot of business though. Buy alot of stuff through work.

[Conejo]

Originally Posted by Opus4

I've said this before & I'll post it again: if you want your local stores to stay in business, buying things to use temporarily & then return them when your internet-ordered item arrives isn't a very nice way to abuse local stores.

And, I've edited out your insulting name of the store.

- Andy

Is there a NICE way to abuse local stores? Because there are a couple of them that I'd... like... to... um... I'll go sit in my corner now.

[Taddeusz]

How can I tell how strong the signal strength is at the wall?

I live in an apartment and only have one connection coming in. If I have everything hooked up I start having signal problems. I have a cable modem, cable phone box, STB, and HDHR. I also have a cable amp in there connected straight to the wall with everything split off it. Right now I have the HDHR taken off the cable and put on an antenna because I was having signal quality issues. But I would like to do away with the antenna and hook my HDHR back to the cable.

[Conejo]

For those playing along at home,

Getting a *usable* Signal Strength measurement can be usually had by connecting your incoming cable wire a directly into a CABLE MODEM or a CABLE BOX and then accessing a service menu.

The measurements you want are
RECEIVE: (also known as: downstream)
SIGNAL STRENGTH in dB
SIGNAL TO NOISE RATIO (SNR) in dB

and maybe TRANSMIT (also known as: upstream)
SIGNAL STRENGTH in dB (how much power the box must use to send a signal back)

NOTE: these numbers can VARY over channels (carrier frequency).

I really wish the Digital Tuner cards would give their measurements in dB instead of 'percentage'.

EXAMPLE METHODS: (unfortunately, these only show SNR)
The forum on DSL Reports gives an example
Hauppauge's WinTV v6 app has a DIGITAL SIGNAL METER

I'll look for more and post back

Here's an interesting thread on DSL Reports: Signal Strength (talks about the HD Home Run) where they referenced JAFA from the SiliconDust forums saying "You need a minimum of 80% (-12dBmV) signal strength for digital cable, 90% recommended."

[stanger89]

Originally Posted by Conejo

I really wish the Digital Tuner cards would give their measurements in dB instead of 'percentage'.

It's actually worse than that, the "signal meters" on most (if not all) digital tuners aren't even displaying signal strength, they're displaying signal quality.

[QueOnda]

Originally Posted by Fuzzy

With your current setup of a 4-way then an 8 way, it is harder to get great results. The problem being, if you put an amp before the 4-way, then the signal after the 4-way's will end up too strong. It is best to have the same drop everywhere, and adjust the input so that they are all at an acceptable level.

You also probably have the signal attenuated at the street, which comcast should be able to turn up if you need it. The best 'quick fix' would actually be to put a +14db amp on the input to the 8-way.

Illustration:


Something to keep in mind, that too strong of a signal can be JUST as bad as too weak. This is WHY Comcast has attenuators at the street.

I got my drop amp and I connected the like the top diagram. Comcast signal to a 4 splitter (7db) only using 2 of them. One for the cable modem and the other for the input of the drop amp.

This is what I'm getting from my cable modem.
Frequency: 735000000 Hz
QAM Mode: 256 QAM
Channel Power: -2.3 dBmV
SNR: 32.974 dB


Upstream Signal
Channel Id: 3
Frequency: 21000000 Hz
Channel Width: 3200000 Hz
Channel Power: 40.5 dBmV

I didn't have a chance to run other test because I had a recording coming on so I had to get it up and going fast. But what this tells me is I have 5.3dbmV for my input cable signal???

I'm going to measure using my cable modem comcast signal and after the drop amp without the 4 spliter (main cable in then to drop amp) to see what it all gives me.

I want the DBM to be 0 =/- 5 dbm, right

Am I missing or misunder standing anything? What should the SNR be on the cable modem?

[Opus4]

BTW: this post has a link to info showing acceptable cable modem signal levels.

- Andy