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Analog cable questions, Amplifiers, 900mhz, 2ghz?

post #1 of 14
12/18/06 at 2:40pm
Thread Starter 
Ok, I'm in a home where the analog cable is split off many times. Lately, one of the TVs in the home has started to show dark bars on the screen which is ruining the picture. In the beginning, I was getting a pretty crisp picture, but now it's noticably blurry and I can see some faint white ghostlike lines in the picture. I went to Radio Shack and bought one of these: http://www.radioshack.com/product/in...entPage=family Well, it did not work too well. The picture turned very noisy and I could still see some faint lines. I had to set the gain almost all the way down which probably just makes it an expensive splitter. I installed it at the main line coming into the home. So I was thinking of buying this 2ghz Monster splitter http://www.amazon.com/exec/obidos/tg...X0DER&v=glance and this Motorola signal booster http://www.amazon.com/exec/obidos/tg...X0DER&v=glance So, should I spend the money and get these two or not waste my money because they might not improve anything?
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post #2 of 14
12/18/06 at 4:50pm
Sounds like a bad TV. Try connecting it to the cable drop input before any splitters.
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post #3 of 14
12/18/06 at 6:52pm
A weak signal would not cause the picture to go blurry. Noisy, yes. Out of focus, no. The faint ghost-like lines sounds like noticeable horizontal scan lines. All point to the TV. Try moving it to one of the locations that works OK on another TV (or move a working TV to this spot).

The noise increase when you added the amplifier could be almost anything. It wouldn't hurt to check that all cables are intact and securely connected. Anyone recently do any construction / house work where the cables are run? Check for nails, etc. that may have accidentally punctured or torn the jacket.
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post #4 of 14
12/18/06 at 7:07pm
Thread Starter 
Positive it's not the TV since all of TVs receiving cable are showing the same problems. When I say blurry, I don't mean it's extremely blurry, but just slightly blurry. I'm also certain it's not scanlines. Removing the splitter and only connecting the main line produces a very good picture. I believe it's because the line is being split off so many times. The Radio Shack amplifier just increased noise and did not improve the picture, so I am skeptical about the 2ghz splitter and motorola booster.
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post #5 of 14
12/19/06 at 6:29am
Have you tried a direct run to each of the TV's, separately? You could have one set that is causing a ground loop between itself and the incoming CATV line.

The Cable is supposed to be grounded to your home's main electrical ground, right where it comes inside. If this ground block is bad (dirty connection, usually), or there is a TV/VCR/tuner/DVD recorder going bad, either could cause a hum loop.
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post #6 of 14
12/19/06 at 5:43pm
also a 2ghz splitter is overkill. you only need a standard 5-1000mhz

analog cable doesn't use the 1-2ghz spectrum, and you'll pay more for a 2ghz splitter
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post #7 of 14
12/19/06 at 6:14pm
Quote:
Originally Posted by kray View Post

also a 2ghz splitter is overkill. you only need a standard 5-1000mhz

analog cable doesn't use the 1-2ghz spectrum, and you'll pay more for a 2ghz splitter

But what about QAM64 or QAM256 coming in on the same line?

Even if you are only subscribing too analog cable, your local cable company will probably be sending it's digital signal over the same cable line. For local CLEAR QAM reception? That is for a STB?

Wouldn't you need a 5-2000Ghz splitter in order to receive those signals if you house has a splitter on it in order to pass those signals?

Aren't they in the higher frequency band, and the 5-900MHz splitter just does not allow pass through?
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post #8 of 14
12/19/06 at 6:42pm
All cable channels - analog, digital 64-QAM, 256-QAM are stuffed together under about ~800 MHz. That's why there's so much intermod.

5 MHz - 40 MHz is reserved for the return path from the STB. 40 MHz - 800 MHz is the forward path. The LNB downconversion from the DBS dishes are above 1 GHz. That's why there are splitters that offer combining of CATV and Satellite on a single coax.

Having the same problem on all TVs is new information. Also, having a very good picture with a direct line confirms you have a line loss problem. How many splits do you go through? Numerous splits plus a long coax run can attenuate the signal down into the noise. Once in the noise, no amount of amplification can recover it.

Try other than Radio Shack. Channelvision makes line distribution amplifiers just for this purpose. I'm using this one in my home http://www.smarthome.com/7750-8.html There are others, but this is the general idea.

You only need enough gain from the home entrance to overcome line losses. Let the amplifier take care of the splitting. Put the amplifier where the coax comes into the house. Take each amplified output directly to each TV. I have 50' runs from my amplifier ("amplified splitter") to 8 locations. All OK.
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post #9 of 14
12/30/06 at 10:41am
Quote:
Originally Posted by GeekGirl View Post

All cable channels - analog, digital 64-QAM, 256-QAM are stuffed together under about ~800 MHz. That's why there's so much intermod.

5 MHz - 40 MHz is reserved for the return path from the STB. 40 MHz - 800 MHz is the forward path. The LNB downconversion from the DBS dishes are above 1 GHz. That's why there are splitters that offer combining of CATV and Satellite on a single coax.

GeekGirl, you rule. thx for a clear explanation and for saving me a few $$$ on a 3-way splitter :-)
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post #10 of 14
1/2/07 at 8:03am
I want to thank Geekgirl too, very helpful information
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post #11 of 14
1/3/07 at 10:06pm
Quote:
Originally Posted by GeekGirl View Post

All cable channels - analog, digital 64-QAM, 256-QAM are stuffed together under about ~800 MHz. That's why there's so much intermod.

5 MHz - 40 MHz is reserved for the return path from the STB. 40 MHz - 800 MHz is the forward path. The LNB downconversion from the DBS dishes are above 1 GHz. That's why there are splitters that offer combining of CATV and Satellite on a single coax.

Having the same problem on all TVs is new information. Also, having a very good picture with a direct line confirms you have a line loss problem. How many splits do you go through? Numerous splits plus a long coax run can attenuate the signal down into the noise. Once in the noise, no amount of amplification can recover it.

Try other than Radio Shack. Channelvision makes line distribution amplifiers just for this purpose. I'm using this one in my home http://www.smarthome.com/7750-8.html There are others, but this is the general idea.

You only need enough gain from the home entrance to overcome line losses. Let the amplifier take care of the splitting. Put the amplifier where the coax comes into the house. Take each amplified output directly to each TV. I have 50' runs from my amplifier ("amplified splitter") to 8 locations. All OK.



This is a bit off topic, but since you have knowledge of channel frequencies I'd like to ask you a question. I have asked this on other forums & so far have not received a definite answer.

I have Comcast & my clear QAM local HD channels are in the 108 to 117 channel number range on my TV. However there are a few other HD channels such as Discovery HD Theater and TNT HD which I cannot get (or find). These are not Premium channels & supposedly a Comcast HD STB is required to get these (and the local HD ones), along with their Digital Classic package. I have the Digital Classic pkg, but only a standard digital STB, not the HD version. I normally feed the cable direct to the TV so I can get the locals in HD. I only use the STB when I need to watch a few of the digital channels.

I don't know if Discovery HD is scrambled or if it just is out of reach of my TV's tuner which goes to channel 125. Discovery HD Theater is cable channel 205, which I realize can be any freq.

Would you have any idea if Comcast would use a freq above channel 125 to transmit Discovery HD on, or any other program? IOW, is it clear QAM but out of my TV's reach? Or is it scrambled? Or both?

Thanks in advance for any information.
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post #12 of 14
1/4/07 at 12:20am
Gotta be encrypted. A TV with a cablecard could be authorized to decode it. An 860 Mhz system does use channels up to 135, whereas some TVs tuners do not go beyond the upper edge of the UHF band (cable channel 125 is 2Mhz lower than broadcast UHF 69)
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post #13 of 14
1/4/07 at 10:01am
I thought about the CableCard scenario since my TV can accept one. But of course the TV can only go to channel 125 which is right at 800MHz. If a cable company uses anything higher, then QAM/CableCard would become useless above that. If I recall, every cable ready TV, VCR & DVD recorder I have owned only goes to channel 125.

If Discovery HD was on cable channel 135 on my TV for example, I would never not be able to receive it without an HD STB.
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post #14 of 14
1/4/07 at 3:28pm
An STB will tell you if the channel is copy-protected. While that's different than encryption, it is usually a pretty good indication. Discovery HD is copy-protected. I don't have a tuner connected, so I can't verify by the RF input.

Copy protection is found in the STB's diagnostic menu under Firewire status byte "5C Implementation" (Power off, then "select" within 5 S). Much more info here: http://www.avsforum.com/avs-vb/showt...86#post3855086
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AVS › AVS Forum › Video Components › Cable, Digital Cable - Non-HDTV › Analog cable questions, Amplifiers, 900mhz, 2ghz?