How many TV's, DVD players, etc.

mivey

Senior Member
can I drive off of a VCR or DVD or XBOX or D/A converter or similar devices? I was wondering if an output cable were connected to the wall outlet would it cause issues, damage or quality wise or would I become the theatre master of my domain? At some scaling limit I know it is not as simple as that so thanks ahead of time for saving me the breaking-the-camel's-back lookup.
 

GoldDigger

Moderator
Staff member
Most types of output from video/audio equipment these days are designed for a 1 to 1 connection only.
Digital outputs use a two way handshake. High frequency coax is designed to be terminated at one point or go through a proper splitter.
Sending your video back out the cable to your neighbors will at some point hit one way amplifiers and be stopped.
But most likely the signal will be in the wrong frequency range and will be ignored.
 

mivey

Senior Member
Most types of output from video/audio equipment these days are designed for a 1 to 1 connection only.
Digital outputs use a two way handshake. High frequency coax is designed to be terminated at one point or go through a proper splitter.
Sending your video back out the cable to your neighbors will at some point hit one way amplifiers and be stopped.
But most likely the signal will be in the wrong frequency range and will be ignored.
Thanks. I was thinking of just in my house as I would not want to run afoul of the law. I was thinking it was an analog output, much like the signal coming in from the cable company but much weaker. I do have HDMI outs but I was thinking about the (what I thought were regular analog) coax outs.
 

GoldDigger

Moderator
Staff member
Coax outputs can be video or video components and audio in separate cables, composite video on one cable, or modulated RF carrying the equivalent of a channel 3 or 4 analog broadcast signal.
The latter is the only one that could easily be split.
We will ignore S-video since that is pretty much obsolete.
The signal that comes out of the cable these days is a multi carrier composite digital signal part of which might be usable by the digital RF input of a TV but most of which is encrypted.
 

ronaldrc

Senior Member
Location
Tennessee
I use to use one of these to watch my VCR out put on any TV hooked to my
comcast cable system.

It is a video/audio modulator. The input is from your RCA analog output jacks from
VCR,DVD etc. and the out put is what ever analog channel you want to assign it
to that this mod. will generate.

Even if you use a small booster on it, its output it is not strong enough to cause any interference out side your home.

I live in a relatively small 1700 sq. home and it would reach any outlet with a good signal with the small booster.




Here is the URL for this unit.http://www.3starinc.com/frequency_agile_uhf_and_cable_tv_channel_video_audio _modulator.html.
 

ronaldrc

Senior Member
Location
Tennessee
I use to use one of these to watch my VCR out put on any TV hooked to my
comcast cable system.

It is a video/audio modulator. The input is from your RCA analog output jacks from
VCR,DVD etc. and the out put is what ever analog channel you want to assign it
to that this mod. will generate.

Even if you use a small booster on it, its output it is not strong enough to cause any interference out side your home.

I live in a relatively small 1700 sq. home and it would reach any outlet with a good signal with the small booster.

Sorry I should have checked that url heres a good one.


http://www.a1components.com/products/advantage-single-channel-digital-modulator-catvuhf__skymod1.aspx
 

gar

Senior Member
141121-1241 EST

If you have a composite video base band signal with a coaxial cable communication path, the source will probably be 50 ohms and the far end of the cable should be terminated with the same impedance to minimize line reflections.

Any taps between the two cable ends should be high impedance and virtually no stub length. This is the ideal. If there are multiple 50 ohm loads along the cable, then signal strength will be reduced and reflections created. Reflections profuce ghost images.

Illustrations of waveforms with open circuit destination impedance can be seen in my photos at:
http://beta-a2.com/cat-5e_photo.html

.


.
 

ronaldrc

Senior Member
Location
Tennessee
141121-1241 EST

If you have a composite video base band signal with a coaxial cable communication path, the source will probably be 50 ohms and the far end of the cable should be terminated with the same impedance to minimize line reflections.

Any taps between the two cable ends should be high impedance and virtually no stub length. This is the ideal. If there are multiple 50 ohm loads along the cable, then signal strength will be reduced and reflections created. Reflections profuce ghost images.

Illustrations of waveforms with open circuit destination impedance can be seen in my photos at:
http://beta-a2.com/cat-5e_photo.html

.


.
No big deal but TV cable is 75 ohms. I'm sure your facts would still apply though.

But I for got to answer the Ops question, with this system as long as you can boost the signal
with amps. the number of Tvs. would be unlimited.

And remember most splitters are not bidirectional and even with the bidirectional ones I'm
not sure the band width would be enough to pass the TV signal in both directions. They are
designed for the Internet. In other words your feed point should be just after your cable enters
your home.
 

Smart $

Esteemed Member
Location
Ohio
No big deal but TV cable is 75 ohms. I'm sure your facts would still apply though.

But I for got to answer the Ops question, with this system as long as you can boost the signal
with amps. the number of Tvs. would be unlimited.

And remember most splitters are not bidirectional and even with the bidirectional ones I'm
not sure the band width would be enough to pass the TV signal in both directions. They are
designed for the Internet. In other words your feed point should be just after your cable enters
your home.
The generic term for amplified and not are active and passive, respectively.

Passive splitters obey the physics of electricity: split the signal and you decrease the signal strength by the inverse number of splits. For example, a 1:2 splitter reduces the signal strength to one half the source. Industry opts to put this reduction in terms of decibels, e.g. -3dB for the 1:2 splitter. How many units you can effectively supply using this method will depend on the input sensitivity of the supplied equipment. Signal strength degradation using this method will be noticeable on analog video signals before digital ones.

You are correct that with an active distribution system, the number is only limited by the equipment's number of outputs.
 

GoldDigger

Moderator
Staff member
I would like to make clear to the readers that an optimal cable splitter is a power splitter. That means that for a 1 to 2 splitter each output gets half the power of the original signal. Since the load impedance remains 75 ohms that means that the output voltage will be 1/sqrt(2) times the input voltage.
A passive resistive splitter will instead produce an output voltage which is 1/2 the input voltage.
 

mivey

Senior Member
I use to use one of these to watch my VCR out put on any TV hooked to my
comcast cable system.

It is a video/audio modulator.
I have a modulator around here somewhere. I use to use it to get from a cheap DVD player to a TV CATV input.
 

mivey

Senior Member
If there are multiple 50 ohm loads along the cable, then signal strength will be reduced and reflections created. Reflections profuce ghost images.
But I for got to answer the Ops question, with this system as long as you can boost the signal
with amps. the number of Tvs. would be unlimited.
I've seen the official video boosters online used for feeding multiple monitors like in an office building. I was just wondering what would happen if I took the CATV out from my DVD player and hooked it onto my house coax cable (after isolating from the CATV company) with 6 or 8 TVs trying to pick up the signal. I think gar is telling me it will look as cheap as it is.
 

mivey

Senior Member
The generic term for amplified and not are active and passive, respectively.

Passive splitters obey the physics of electricity: split the signal and you decrease the signal strength by the inverse number of splits. For example, a 1:2 splitter reduces the signal strength to one half the source. Industry opts to put this reduction in terms of decibels, e.g. -3dB for the 1:2 splitter. How many units you can effectively supply using this method will depend on the input sensitivity of the supplied equipment. Signal strength degradation using this method will be noticeable on analog video signals before digital ones.

You are correct that with an active distribution system, the number is only limited by the equipment's number of outputs.
Are the signal strength of a common DVD and the sensitivity of a common TV published or do they just assume you will not feed more than one or two TVs from one DVD player?

I know I can feed more than one TV (at least from some players) but add more TVs and 50 ft of cable plus splitters...
 

Smart $

Esteemed Member
Location
Ohio
Are the signal strength of a common DVD and the sensitivity of a common TV published or do they just assume you will not feed more than one or two TVs from one DVD player?

I know I can feed more than one TV (at least from some players) but add more TVs and 50 ft of cable plus splitters...
Don't recall ever seeing them published.

I recall passively splitting CATV with a 1:3 splitter with no "realized" degradation years ago. On scenarios of 4 or more, I've always used a distribution amp of some sort.
 

egnlsn

Senior Member
Location
Herriman, UT
Occupation
A/V/Security Technician
Most CATV systems are designed to have a signal level of 15-20dBmV at the tap on or pedestal. RG6 loses ~6.55dB/100ft, so doing the math tells you about how much signal strength you should have at the house.

While yes, a slitter is a power divider, in CATV the measurement is signal strength, not power. dBmV, mot mV. 2-way splitters lose from ~3.2dBmV to 4.2dBmV, depending on frequency an manufacturer.

3 devices should rune just fine with just a splitter, while 4 or more may need to be amplified.

Splitters used in CATV are bi-directional. The bandwidth is 5-1000MHz. The return path is 5-42MHz, while the forward path is 50-*1000MHz.

If there are digital channels in a cable system, those residential modulators can't be used - digital cable uses the bandwidth all the way up to 750MHz, 860 in some systems.
 

mivey

Senior Member
Most CATV systems are designed to have a signal level of 15-20dBmV at the tap on or pedestal. RG6 loses ~6.55dB/100ft, so doing the math tells you about how much signal strength you should have at the house.

While yes, a slitter is a power divider, in CATV the measurement is signal strength, not power. dBmV, mot mV. 2-way splitters lose from ~3.2dBmV to 4.2dBmV, depending on frequency an manufacturer.

3 devices should rune just fine with just a splitter, while 4 or more may need to be amplified.

Splitters used in CATV are bi-directional. The bandwidth is 5-1000MHz. The return path is 5-42MHz, while the forward path is 50-*1000MHz.

If there are digital channels in a cable system, those residential modulators can't be used - digital cable uses the bandwidth all the way up to 750MHz, 860 in some systems.
Thanks. Any idea what the signal strength is from a DVD player or similar?
 

egnlsn

Senior Member
Location
Herriman, UT
Occupation
A/V/Security Technician
Most devices that I've measured in the past put out ~5dBmV or so -- enough to run the TV set where they are. You could probably split it 2 ways as long as both outlets are fairly close to the DVD player. RG6 loses ~1.6dB/100' at channel 2. If the DVD player has an output of 5dBmV and the 2-way splitter loses ~3.5dB, that leaves ~1.5dBmV to go to the TVs. Personal preference is that is not enough, although the F.C.C. says it should work (as long as the TVs are within ~50'or so. And that is assuming that it puts out a minimum of 5dBmV. It could only put out around 3.

Without a meter to measure it, there is no way to know for sure.
 

mivey

Senior Member
Most devices that I've measured in the past put out ~5dBmV or so -- enough to run the TV set where they are. You could probably split it 2 ways as long as both outlets are fairly close to the DVD player. RG6 loses ~1.6dB/100' at channel 2. If the DVD player has an output of 5dBmV and the 2-way splitter loses ~3.5dB, that leaves ~1.5dBmV to go to the TVs. Personal preference is that is not enough, although the F.C.C. says it should work (as long as the TVs are within ~50'or so. And that is assuming that it puts out a minimum of 5dBmV. It could only put out around 3.

Without a meter to measure it, there is no way to know for sure.
Thanks. That's the missing piece.
 

hbiss

EC, Westchester, New York NEC: 2014
Location
Hawthorne, New York NEC: 2014
Occupation
EC
The RF output of a DVD player is old technology for those luddites who haven't replaced their player with a Blue Ray or still don't have a high def flat screen TV. All they can expect is old standard definition- hardly worth the trouble. You want to have high def, you want to distribute either the component or HDMI output of like a Blue Ray player or cable box and there are devices that will do that, even using CAT6 cable.

-Hal
 

mivey

Senior Member
The RF output of a DVD player is old technology for those luddites who haven't replaced their player with a Blue Ray or still don't have a high def flat screen TV. All they can expect is old standard definition- hardly worth the trouble. You want to have high def, you want to distribute either the component or HDMI output of like a Blue Ray player or cable box and there are devices that will do that, even using CAT6 cable.

-Hal
I do have HDMI and component to a projector and HDMI to my flat screens. If I were building a house from scratch, I would do something different but I was just wondering about someone using the existing coax that is already run through an old house so they could play a movie or something in multiple rooms by just connecting to a DVD player's coax out signal. Doesn't sound like it would be very practical without a booster.
 
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