How to amplify signal?

[artisticcheese]

Hello,

I have structured cabling in a house which allows me to distribite video through the house from single outlet. My RF output connected to that outlet right now and I can see picture on other TVs but it looks grainy. I have been told that I need to amplify signal to prevent this and I'm not sure I know what needs to be done.
Can somebody send me a link or explain to me what needs to be done to remove those grainy pictures.

 

[RandallA]

You'll need to provide more info on your equipment. LNBs, receivers, switches, etc. If possible describe how each TV is connected and how long the cable runs are.

 

[artisticcheese]

Standard RF output of receiver connects through central console to the rest of the house. NOt sure how long cables are. At this point it's not related wether it's dish or not dish since it's standard RF output of receiver going in.

 

[RandallA]

"At this point it's not related wether it's dish or not dish since it's standard RF output of receiver going in."

True, but it will give us an idea how you have it setup. How many more TVs are you trying to feed?

 

[rcbridge]

How many tv's are involved? Are you using passive splitters?
How long are the cable runs?

 

[Lorenzo]

It sounds to me that you are distributing the rf- possibly ch 3 or ch 4 to the other outlets in the house. If you have multiple cables at each outlet possibly you have a return cable that goes back to a common point (or the common point might be right at your main tv location) where it is split and then sent to all the outlets. If the received signal is slightly or somewhat grainy (snowy) a run of the mill cable tv type 10 db amplifier (50-550 Mhz bandwidth) single output style would be a good start. The best place to put this would be at the output of the receiver. You'll also need a short coaxial jumper cable to insert the amp into the system.

If the received signal is very snowy to extremely snowy (it's getting hard to tell what sports team you're watching or if it's really bad (hard to tell a man from a women) you might have more than a low signal problem (maybe a bad connection or splitter wrongly wired) at your common point.

http://store1.yimg.com/I/abccables-store_1865_128574487 ...is a picture of the type of amplifier I'm talking about. This same style is sold under many brand names and often has a silver metal case. The 50-500 Mhz type is good for ch 3 or 4 and cable channels up to the 70's. A VHF/UHF 50- 900 Mhz type is for ch 3 or 4 and TV antenna channels.
Local prices I see at Radio Shack and at dept. stores run in the $10 to $20 range.

 

[bnaivar]

Rule #1

If you amplify grainy pictures you get amplified grainy pictures.

(Make sure the amp is placed BEFORE the signal loss, not after.)

 

[artisticcheese]

How many tv's are involved? Are you using passive splitters?
How long are the cable runs?

I'm using RF modulator to convert RCA signal into RF and then distribute through structured cabling.
I still have 3 questions.
1. On the back of RF modulator there is a jumper which referes to something "75 ohm". What is that supposed to be set to?
2. What kind of cables do I need to use to connect to amlifier and then amplifier to a wall. Tiny cable or big fat cable which Dish installer left behind. Plugs look the same but one cable is much thicker then another one.
3. I'm distributing on Ch3, is this what I need? http://cgi.ebay.com/Recoton-Video-Signal-Amplifier-V310UL_W0QQitemZ5817106932QQcategoryZ79875QQrdZ1QQcmdZViewItem

 

[rcbridge]

Quote[[I'm using RF modulator to convert RCA signal into RF and then distribute through structured cabling.
I still have 3 questions.
1. On the back of RF modulator there is a jumper which referes to something "75 ohm". What is that supposed to be set to?
2. What kind of cables do I need to use to connect to amlifier and then amplifier to a wall. Tiny cable or big fat cable which Dish installer left behind. Plugs look the same but one cable is much thicker then another one.
3. I'm distributing on Ch3, is this what I need?.

The cable used for video has an impedance of 75ohms, since you are at channel 3 or 4
you can either use RG-59 or RG-6. They have F type connectors.
You will select channel 3 or 4 (on the modulator), it is best to select the channel that is not used in your area. (OTA channel). Set your other TV's to match the channel you chose.
As far as an amplifier, the one you linked to, they don't give much on spec's, but it does cover the frequency range that you need (channel 3 or 4) so I dont know how it will perform.
Is there a cable modem involved?
How many splits are you looking to have, (this may help in finding the correct amp for you)?

 

[artisticcheese]

Quote[[I'm using RF modulator to convert RCA signal into RF and then distribute through structured cabling.
I still have 3 questions.
1. On the back of RF modulator there is a jumper which referes to something "75 ohm". What is that supposed to be set to?
2. What kind of cables do I need to use to connect to amlifier and then amplifier to a wall. Tiny cable or big fat cable which Dish installer left behind. Plugs look the same but one cable is much thicker then another one.
3. I'm distributing on Ch3, is this what I need?.

The cable used for video has an impedance of 75ohms, since you are at channel 3 or 4
you can either use RG-59 or RG-6. They have F type connectors.
You will select channel 3 or 4 (on the modulator), it is best to select the channel that is not used in your area. (OTA channel). Set your other TV's to match the channel you chose.
As far as an amplifier, the one you linked to, they don't give much on spec's, but it does cover the frequency range that you need (channel 3 or 4) so I dont know how it will perform.
Is there a cable modem involved?
How many splits are you looking to have, (this may help in finding the correct amp for you)?

Signal is going to be slit 5 ways but only 1 TV is hooked up yet (not sure if it matters).
Image is a little grainy right now with direct output (without amplifier).
There is no cable moded involved just my DISH.

 

[Lorenzo]

I agree with rcbridge. The pictured modulator is the same as the one I referred to. They commonly have 10 db gain.

If your 75 ohm switch is near the video input port of your modulator and there is also a video out port on the modulator the switch is probably used to either terminate the video input in 75 ohms or bridge the video signal to the output video port to feed a local monitor or another modulator. Chances are in your case the video out port is unused and the switch should be in the 75 ohm position. If the switch is incorectly set the modulated video on ch 3 or 4 will be dim or washed out (low contrast).

What model of modulator do you have and does it specify it's rf output level strength in DbMv? There are modulators with +10, + 25, +45, and +60 DbMv output commonly available. The +10 model might be a little underpowered if your distribution wiring isn't the most efficient but the +25 model should be adequate and the +45 and +60 models are enough to power a small hotel or apartment building with a reasonably efficient distribution design.

 

[artisticcheese]

I agree with rcbridge. The pictured modulator is the same as the one I referred to. They commonly have 10 db gain.

If your 75 ohm switch is near the video input port of your modulator and there is also a video out port on the modulator the switch is probably used to either terminate the video input in 75 ohms or bridge the video signal to the output video port to feed a local monitor or another modulator. Chances are in your case the video out port is unused and the switch should be in the 75 ohm position. If the switch is incorectly set the modulated video on ch 3 or 4 will be dim or washed out (low contrast).

What model of modulator do you have and does it specify it's rf output level strength in DbMv? There are modulators with +10, + 25, +45, and +60 DbMv output commonly available. The +10 model might be a little underpowered if your distribution wiring isn't the most efficient but the +25 model should be adequate and the +45 and +60 models are enough to power a small hotel or apartment building with a reasonably efficient distribution design.

Wow. I'd have to take a look when will be home about those specifics.
Thanks for all your help, I'll post info later today when will have change to examine modulator.

 

[nmoulton]

I have just about the same setup in my house. I have a Dish network 508 DVR and I ran a cable from its channel 4 RF output to the basement, there I run it through a 1 to 4 splitter and distribute it to the prewired coax outlets thoughout my house. When I first did this, I also had a grainy picture due to the long runs of cable and the splitter. I bought an RF amp at K-mart, it has one coax input and one coax output, and it cost $20. I put this in line before the splitter so there is only about 8 ft of coax before the signal gets amplified. This has worked great. I have 3 TVs hooked up downline, and all pictures are now crystal clear. (I have 2, 20" TVs and a 13" TV connected.)

It is true that if you amplify snow, you will get more snow, but this is the exact case where an simple amp works well, you are counteracting the splitting and the long runs of coax. And the signal where you are putting the amp has no snow.

Also, since the 508 DVR has a UHF remote, it means I can sit in front of any TV in the house and control the DVR the same as if I was in front of it. It is a great system. I actually bought 3 extra UHF remotes from ebay so I can leave them in the different rooms. It's a great set up!

-Norm

 

[artisticcheese]

I agree with rcbridge. The pictured modulator is the same as the one I referred to. They commonly have 10 db gain.

If your 75 ohm switch is near the video input port of your modulator and there is also a video out port on the modulator the switch is probably used to either terminate the video input in 75 ohms or bridge the video signal to the output video port to feed a local monitor or another modulator. Chances are in your case the video out port is unused and the switch should be in the 75 ohm position. If the switch is incorectly set the modulated video on ch 3 or 4 will be dim or washed out (low contrast).

What model of modulator do you have and does it specify it's rf output level strength in DbMv? There are modulators with +10, + 25, +45, and +60 DbMv output commonly available. The +10 model might be a little underpowered if your distribution wiring isn't the most efficient but the +25 model should be adequate and the +45 and +60 models are enough to power a small hotel or apartment building with a reasonably efficient distribution design.

I have Recoton V647 modulator. I don't know specs of that thing (it's on this page http://www.installersoutlet.com/modulator.html ). Switch at the back of modulator has 2 positions Ohm - 75K - 1K. Right now it's in 75 K.
SO which amplifier is best in my case?

 

[Barry Erick]

Right now you have a 5 way splitter. This has a big loss. You need to feed it with more than the 10db gain of the amp to overcome this loss. Amplifying it after the splitter will only amplify the noise.

 

[artisticcheese]

So how many dB I shall be buying?

 

[Lorenzo]

Your V647 looks to be a +10 DbMv or less modulator. You probably will be feeding a 6 or 8 way splitter which have a 9 or 10 loss. Drop cable (RG59 or RG6 typ)e has less than 1 db of loss in 50 feet. If you add the losses you have about 10 db in loss. Using one of the 10 db amplifiers means that you should have the same signal level at your outlets (not more than 50 cable feet away) as the modulator puts out. I think the 10 db amp is just about right for thr job.

Keep in mind the graniness level at the output of the modulator is the best you will able to get at the remote locations. To get a less grainy signal you'll have to get a different modulator or in other words your modulator determines the graininess. A correct distribution system can only send this quality to the remote locations it cannot improve on it.

 

[Lorenzo]

Something I left out of my DbMv calculations that some may not be aware of is that a very good tv signal level to have at your tv is +3 DbMv. Levels above +3 won't look any better than the +3 DbMv level.

 

[SimpleSimon]

Signal is going to be slit 5 ways but only 1 TV is hooked up yet (not sure if it matters).

Yes, it DOES matter. As already mentioned, a 5-way split is big loss, but to stick to the "only 1 TV hooked up yet". What that means to me is that you have FOUR unterminated coax runs that are sucking every kind of RF noise you can imagine. Not good for signal quality.

 

[artisticcheese]

So if purchase mode dB amplifier (20 as opposed to 10) can I hurt anything by that. Since I don't know how powerfull amplifier shall be it's ok to buy more powerfull one then not powerfull one?