Combining and Diplexing Signals

[charlesrshell]

Is there a rule of thumb for what signals that can be combined together? How about signals that can be diplexed? I am not too familiar with the different kinds of TV signals. What is the difference between OTA antenna, modulated, cable, and satellite signals?

 

[rcbridge]

Diplexing two signals is a matter of the carrier frequencies involved.
A diplex filter (diplexer) is simply a low pass and a high pass filter in one package.

OTA and cable use a lot of the same frequencies for broadcasting so you should not mix them.

Satellite uses a higher frequency range, so typically you can diplex them, with cable or OTA.

 

[highdefjeff]

Charlie,

First, let's get modulated out of the way. All of the signals we use are modulated.

Modulation is the term applied to a carrier wave that has been "modified" to carry a distinct message or information.

There are four components of signal transfer.

1. The data signal is the wave that actually contains the information that needs to be sent to the receiver.

2. The carrier signal is the wave that carries the data signal.

3. Modulation is the process that encodes the data signal into the carrier signal and creates the radio wave that is actually transmitted by the antenna to propagate.

and,

4. The antenna is the device used to transmit and receive signals such as radio waves.

There are basically three types of modulation or types of modification to a signal.

The basic carrier wave is like a sine wave. It looks like a wave on the ocean. It goes up and down in the same amount of time, everytime, measured from any two similar points, like from one crest to another, or one trough to another. That measurement is it's frequency, or how frequently it repeats. Modulation that alters a carrier wave in this aspect is called FM modulation. If the data signal is a digital signal, the FM technique is called frequency shift keying.

The carrier wave raises the same distance and drops the same distance from a centerline between the crest and trough. This distance, or height, is amplitude. Sort of like altitude. Modulation (change) of this aspect is refered to as AM modulation. The amplitude modulation is called amplitude shift keying, or ASK, when the data signal is a digital signal.

Phase shifting or phase shift keying is a technique that represents digital data by shifting the period of the carrier signal.

So modulation is the modification of any signal to carry distinct information by changing the original (carrier) waves characteristics. It happens in satellite transponders and in your VCR with the channel 3-4 output. Receivers that understand the information presented, de-modulate and remove the information from the carrier to present it to you.

The differences between the OTA, satellite, and cable in the context of diplexers...if there is a way to diplex satellite with digital cable, I'm not aware.

 

[charlesrshell]

Charlie,

First, let's get modulated out of the way. All of the signals we use are modulated.

Modulation is the term applied to a carrier wave that has been "modified" to carry a distinct message or information.

There are four components of signal transfer.

1. The data signal is the wave that actually contains the information that needs to be sent to the receiver.

2. The carrier signal is the wave that carries the data signal.

3. Modulation is the process that encodes the data signal into the carrier signal and creates the radio wave that is actually transmitted by the antenna to propagate.

and,

4. The antenna is the device used to transmit and receive signals such as radio waves.

There are basically three types of modulation or types of modification to a signal.

The basic carrier wave is like a sine wave. It looks like a wave on the ocean. It goes up and down in the same amount of time, everytime, measured from any two similar points, like from one crest to another, or one trough to another. That measurement is it's frequency, or how frequently it repeats. Modulation that alters a carrier wave in this aspect is called FM modulation. If the data signal is a digital signal, the FM technique is called frequency shift keying.

The carrier wave raises the same distance and drops the same distance from a centerline between the crest and trough. This distance, or height, is amplitude. Sort of like altitude. Modulation (change) of this aspect is refered to as AM modulation. The amplitude modulation is called amplitude shift keying, or ASK, when the data signal is a digital signal.

Phase shifting or phase shift keying is a technique that represents digital data by shifting the period of the carrier signal.

So modulation is the modification of any signal to carry distinct information by changing the original (carrier) waves characteristics. It happens in satellite transponders and in your VCR with the channel 3-4 output. Receivers that understand the information presented, de-modulate and remove the information from the carrier to present it to you.

The differences between the OTA, satellite, and cable in the context of diplexers...if there is a way to diplex satellite with digital cable, I'm not aware.

Thanks Jeff

 

[vegassatellite]

You can diplex digital cable on to the same line as satellite. You have to be mindful that digital cable has a return path that is typically below 40mhz, where many diplexers aren't rated down to those frequencies. A 5-2050mhz diplexer will work. The one real problem I've found with diplexing digital cable is that the signal levels and quality are already pretty poor at many customer's homes simply because the cable company doesn't have a well-run system. At least its that way in many of Cox's markets.

 

[charlesrshell]

You can diplex digital cable on to the same line as satellite. You have to be mindful that digital cable has a return path that is typically below 40mhz, where many diplexers aren't rated down to those frequencies. A 5-2050mhz diplexer will work. The one real problem I've found with diplexing digital cable is that the signal levels and quality are already pretty poor at many customer's homes simply because the cable company doesn't have a well-run system. At least its that way in many of Cox's markets.

So satellite can be diplexed with cable, OTA, and agile modulated. So can cable, OTA, and agile modulated be diplexed with each other if there is ever a need? What about combining these signals too? Can any of them not be combined together?

 

[rcbridge]

So can cable, OTA, and agile modulated be diplexed with each other if there is ever a need? What about combining these signals too? Can any of them not be combined together?

Cable uses a frequency range of 5-860mhz (top end may vary by individual system).
5-42 for return (upstream) 50-860 for forward (downstream).

OTA channel 2 is about 50mhz and goes up from there with each channel about 6mhz apart.

This scenerio will give you overlapping frequencies so this is a no go.

With the help of a channel deletion filter(s) you could attenuate a channel or so within the cable or OTA band and inject a modulated channel in that space!

 

[charlesrshell]

Cable uses a frequency range of 5-860mhz (top end may vary by individual system).
5-42 for return (upstream) 50-860 for forward (downstream).

OTA channel 2 is about 50mhz and goes up from there with each channel about 6mhz apart.

This scenerio will give you overlapping frequencies so this is a no go.

With the help of a channel deletion filter(s) you could attenuate a channel or so within the cable or OTA band and inject a modulated channel in that space!

OK, thanks rcbridge. That clears it up for me.

 

[OrangeandBlue33]

So, is it feasible to combine the output of a 508 receiver (Channel 4) with the modulated output of a 722 receiver (Channel 21) with a cheap splitter? What MHz ranges would I be dealing with if this is possible. I'm just wondering if the splitter I already have will do the job, or will I need a certain range that is different? The one I currently have is for 400-1750MHz.

Thanks!

 

[vegassatellite]

So, is it feasible to combine the output of a 508 receiver (Channel 4) with the modulated output of a 722 receiver (Channel 21) with a cheap splitter? What MHz ranges would I be dealing with if this is possible. I'm just wondering if the splitter I already have will do the job, or will I need a certain range that is different? The one I currently have is for 400-1750MHz.

Thanks!

Don't you mean 40-1750?

If so, you're good to go. Just reverse the splitter and voila! a combiner. Keep in mind that the modulated ch. 21 of the 722 is going to be much stronger than ch 4 because it is intended to run through a lot of house wiring versus the channel 4 being intended for only a few feet of cable. Better to either use a directional coupler and hook the ch 21 to the TAP port or re-modulate the 722 to a higher channel to balance out the signal at the end of the run.

 

[OrangeandBlue33]

Don't you mean 40-1750?

If so, you're good to go. Just reverse the splitter and voila! a combiner. Keep in mind that the modulated ch. 21 of the 722 is going to be much stronger than ch 4 because it is intended to run through a lot of house wiring versus the channel 4 being intended for only a few feet of cable. Better to either use a directional coupler and hook the ch 21 to the TAP port or re-modulate the 722 to a higher channel to balance out the signal at the end of the run.

Thanks vegassatellite. I hooked it up with the one I had this morning and it worked fine. Thanks again for the assistance.

 

[theoak]

I am going to resurrect this thread.

This is my setup:

The antenna OTA cable goes from my attic down to the cable box on the outside of the house. That OTA cable is the input of a splitter, to the individual "room" cables.

The "satellite" cable obviously goes directly to my room.

Therefore I have two cables going into my room.

1. A satellite cable.
2. A "room" cable (originating for the cable box at the side of my house).

My goals are:

1. Get OTA to my 722.
2. Use the TV2 of my 722 and distribute that signal back to the another room of my home.

Case 1: "Room" cable carries only 722 output.

If I connect the "room" cable to the TV2 out of the 722 and in the cable box on the side of my house put that room cable as the input of the splitter, I get signal to my other TVs fine enough. The video quality is good with a little bit of snow.

However, I do not get OTA to my 722.

Case 2: "Room" cable carries both the OTA signal and the 722 output.

Using a simple splitter in my bedroom, I connect the room cable to the antenna in and the TV2 out on the 722.

In the cable box on the side of my home I have a splitter. On the "in" I have the room cable. On an "out" I have my OTA cable from my antenna. On the other "out" I have a cable going to another room.

This setup allows the 722 to get the OTA signal and also the other room to get the signal from 722.

With this setup the picture quality is poor. Very snowy. Watchable still, but snowy. The intent is for the kids, so they do not seem to mind, however, if I eventually want to add more rooms, I do not see the quality getting better.

I imagine it has to do with the OTA signal coming one way and the 722 signal going the other way on the same cable.

Am I making sense so far?

Case 3: Use the satellite signal to carry the OTA signal.

I have not tried this yet.

Before I went through the effort however I thought I would ask and get feedback.

I could go through the work of having the OTA antenna cable in my attic go to my dish. From there I could use a diplexer and carry the OTA signal over the satellite cable.

Once in my room, I could use another diplexer to split the signal up to the satellite input and the OTA input to my 722.

I could then use my "room" cable and connect that to the TV2 out on the 722. This way the "room" cable only carries the output from the 722. I would then connect that "room" cable as the "in" to the splitter in the cable box at the side of my home.

What has people's experiences been with using the satellite cable to also carry the OTA signal?

 

[topcat0399]

I am going to resurrect this thread.

This is my setup:

The antenna OTA cable goes from my attic down to the cable box on the outside of the house. That OTA cable is the input of a splitter, to the individual "room" cables.

The "satellite" cable obviously goes directly to my room.

Therefore I have two cables going into my room.

1. A satellite cable.
2. A "room" cable (originating for the cable box at the side of my house).

My goals are:

1. Get OTA to my 722.
2. Use the TV2 of my 722 and distribute that signal back to the another room of my home.

Case 1: "Room" cable carries only 722 output.

If I connect the "room" cable to the TV2 out of the 722 and in the cable box on the side of my house put that room cable as the input of the splitter, I get signal to my other TVs fine enough. The video quality is good with a little bit of snow.

However, I do not get OTA to my 722.

Case 2: "Room" cable carries both the OTA signal and the 722 output.

Using a simple splitter in my bedroom, I connect the room cable to the antenna in and the TV2 out on the 722.

In the cable box on the side of my home I have a splitter. On the "in" I have the room cable. On an "out" I have my OTA cable from my antenna. On the other "out" I have a cable going to another room.

This setup allows the 722 to get the OTA signal and also the other room to get the signal from 722.

With this setup the picture quality is poor. Very snowy. Watchable still, but snowy. The intent is for the kids, so they do not seem to mind, however, if I eventually want to add more rooms, I do not see the quality getting better.

I imagine it has to do with the OTA signal coming one way and the 722 signal going the other way on the same cable.

Am I making sense so far?

Case 3: Use the satellite signal to carry the OTA signal.

I have not tried this yet.

Before I went through the effort however I thought I would ask and get feedback.

I could go through the work of having the OTA antenna cable in my attic go to my dish. From there I could use a diplexer and carry the OTA signal over the satellite cable.

Once in my room, I could use another diplexer to split the signal up to the satellite input and the OTA input to my 722.

I could then use my "room" cable and connect that to the TV2 out on the 722. This way the "room" cable only carries the output from the 722. I would then connect that "room" cable as the "in" to the splitter in the cable box at the side of my home.

What has people's experiences been with using the satellite cable to also carry the OTA signal?

listen, people get so wrapped up about the terms IN vs OUT on simple splitters. There really is no such thing. an IN is the same as an OUT and vs versa. whenever you connect any cables to a simple splitter, it is the same as cutting off the ends of all the cables, and twisting together all of the center conductors, and then twisting togther all of the braids.

modulated TV Band RF waves have no specific direction per se. They just propagate from thier source. Like the signals coming from your antenna, and the signal coming from TV2 output of the 722. The antenna puts those waves on the wire, and the 722 TV2 puts those waves on the wire. those waves are available to any device connected anywhere in the system to those wires. As long as no input source is propagating TV band waves on the same freq, it can usssually work to just insert them all on the same wire (even from diffrent sources/locations/devices). There needs to be some separation between the waves however (i like to use 3 channel separation) so that waves have little chance of interfering.

get it?

k lesson over.


i take it that your dish isnt grounded to a ground block.

so if i were you i would:

cut the cable running to your 722 from the dish, put on new connectors, insert a diplexor there, connect the Dish cable to the SAT side connect the cable to the receiver to the IN/OUT side.

disconnect your antenna cable from the splitter at the cable box and connect it to the UHF side of that diplexor.

at the 722 - use another diplexor in reserve and split it all back out EXCEPT.....
run the UHF side of that diplexor into a 2 way splitter.

connect the TV2 Ch 21-69 OUT to that splitter, and then connect your ROOM cable to that splitter, sending ALLl modulated signals down to your cable box.

then consider installing an AMPLIFIED splitter either in the cable box (it would need 110V power) and connect all other ROOM cables to it or put a TV Band amp after the 3way splitter at the 722 boosting the signal down to the simple splitter in your cable box. connect all ROOM cables to that

this way you get antenna and TV2 at all other rooms.

you would have to be careful of the channel selections for TV2 from the 722, so that they dont stomp on the antenna channels.

you didnt mention if your OTA has any kind of amplifiers in its setup.



that would be the quickest way to make it all work.


personally, when that dish was put in, I would have run the Dish cables to your cable box, and diplexed up to the 722, provided the existing cabling were up to it. this makes for simple grounding, home distribution, and connection changes. all future cables of anykind would be "home run" to that cable box.


good luck

 

[theoak]

Thank you for your response.

Actually "search" was my friend here, so I actually found similar posts and went ahead and did it.

As far as the "in/out lesson" ... I completely understand your point. With that being said, being in the computer industry and having to create support cases, if I do not provide as much detail as possible, the case will come back, "we need more information". I was just simply trying to be as detailed as possible.

I do appreciate your feedback.

What I ended up doing was bringing the antenna cable out to the dish. Added my diplexer there, and then one in the room.

This way the TV2 out normal cable, going out to my cable box, only carries the output signal from the 722. Out at the cable box I have that cable as the input to the splitter to the other room cables.

I now have no snow. I have TV1 and TV2 from the 722 getting sent out and it works great.

I have not used an amplifier anywhere in my setup.

It appears that with my normal room cable carrying both the satellite output and antenna signals, that there was too much interference. Splitting them up did the trick.

 

[topcat0399]

Thank you for your response.

Actually "search" was my friend here, so I actually found similar posts and went ahead and did it.

As far as the "in/out lesson" ... I completely understand your point. With that being said, being in the computer industry and having to create support cases, if I do not provide as much detail as possible, the case will come back, "we need more information". I was just simply trying to be as detailed as possible.

I do appreciate your feedback.

What I ended up doing was bringing the antenna cable out to the dish. Added my diplexer there, and then one in the room.

This way the TV2 out normal cable, going out to my cable box, only carries the output signal from the 722. Out at the cable box I have that cable as the input to the splitter to the other room cables.

I now have no snow. I have TV1 and TV2 from the 722 getting sent out and it works great.

I have not used an amplifier anywhere in my setup.

It appears that with my normal room cable carrying both the satellite output and antenna signals, that there was too much interference. Splitting them up did the trick.

glad you made it work.

 

[AdamGott]

Interesting. I was unaware that one could diplex an external antenna to a 622/722 since they are already using diplexers (I think?) to go to tv2. So what you are saying is that we CAN still hook up an external antenna near the dishes and just diplex the signal in through there? I was going to put up an external antenna this weekend but I didn't want to mess with running coax to both 622's and drill holes in the exterior walls of the house (including one basement install). This would be a much more elegant solution for me.

I presently get all of my locals with a pair of amplified rabbit ears/uhf loop but I can't seem to find one position that can get all of the channels well so I have to mess with it a lot if I watch a different channel.

So do I just go buy a couple of diplexers and wire them in? Is there anything special that I need to know? I would like to feed the external antenna to both 6ss's so should I split it first and then use two diplexers or is that going to be too much signal loss?

Thanks for any and all input.

 

[tastim]

Interesting. I was unaware that one could diplex an external antenna to a 622/722 since they are already using diplexers (I think?) to go to tv2. So what you are saying is that we CAN still hook up an external antenna near the dishes and just diplex the signal in through there? I was going to put up an external antenna this weekend but I didn't want to mess with running coax to both 622's and drill holes in the exterior walls of the house (including one basement install). This would be a much more elegant solution for me.

I presently get all of my locals with a pair of amplified rabbit ears/uhf loop but I can't seem to find one position that can get all of the channels well so I have to mess with it a lot if I watch a different channel.

So do I just go buy a couple of diplexers and wire them in? Is there anything special that I need to know? I would like to feed the external antenna to both 6ss's so should I split it first and then use two diplexers or is that going to be too much signal loss?

Thanks for any and all input.

If the system is already diplexed to another TV, you don't more diplexers... just splitters.

 

[TheKrell]

That "diplexer" that splits the single coax to feed both tuners is actually called a "separator".

If I understand what you want to do, you will need 4 diplexers and a splitter. The splitter is used to split your antenna lead and feed into the two diplexers which go on the top of your two cables going to your receivers. The other two diplexers go at your receiver before the separators.

All clear now?

 

[AdamGott]

Yes, crystal clear now. Thanks!

I am going to just try and hook up my amplified rabbit ears tomorrow and see if that works and then I will go find a better antenna. This will be pretty cool if it works - I will finally be able to get all of the HD locals without messing with rabbit ears and running new coax.

 

[AdamGott]

Thanks for the advice/help. I got it all working this last weekend and got rid of a couple of rabbit ears in my house. At first I built that coat hanger HDTV antenna and it worked very well for the UHF channels (but it is very directional so if you have channels coming from different directions it probably won't work very well for you) but with one of my locals using VHF it just wouldn't cut the mustard so I ended up buying a $35 antenna and putting it in my attic.

I did find that this messed up my picture quality on my tv2's but I switched them from cable channel 73 to UHF channel 21 and they look good again.