combining multiple units through a modulator?

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Mr Tony

Thread Starter
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Supporting Founder
Nov 17, 2003
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Mankato, MN
Since I mainly have FTA, I'm posting it here

So I was over at Sadoun’s site today and I see these Vsat modulators
http://www.sadoun.com/Sat/Order/VSAT/Modulators.htm

So I check them out and there are combiners, demodulators, and micro modulators.
12/16/24 channel combiner, etc

Now I guess here is my question.

I’ve seen them other boxes where you combine 1 or 2 inputs and send it through the house to other TV’s and they just tune a channel. But I was thinking something a little bigger…something that I can 6 or 7 items into. With a StarChoice box, Dish, OTA and 9 FTA boxes I’d like to have one central spot and pump it through the house.

Can I get by with just one of the combiners like so?
http://www.sadoun.com/Sat/Products/JVI/95-TPHC12-Passive-Combiner.htm

or do I need the combiner above and a demodulator for each input I need (to designate a channel)
http://www.sadoun.com/Sat/Products/JVI/95-TMD-Micro-Demodulator.htm

I know some people have worked in cable TV or setups like this. How does it work (or am I just smoking something)
 
Krapola

Krapola

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Jan 10, 2006
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Fairfield, Cali
Mod per input into Combiner is the cleanest...It will offer the best linearity....Of course you will have a loss of S/N...Anything Modulated does down a transmission line..
 
Sadoun

Sadoun

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Feb 27, 2005
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Columbus, OHIO
Ice,

You will need a combiner and several modulators (not demodulators).

Basically, the modulator will take the signal from the UHF/VHF or A/V source and converts it to a channel between 2- 135.

Once converted, then you can connect it to one of the inputs on the combiner.

Commercial level modulator

Consumer level Modulator

So if you want to create a mini home CATV network of 12 channels, you will need Qty 12x Modulators, and Qty 1x 12-way-Combiner
 

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M

Mr Tony

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Oh ok...now I get it

I have one of those old ChannelPlus 2 channel modulators and it works pretty well but was thinking of something a little more advanced.
 
D

dish_in_the_sky

SatelliteGuys Family
May 18, 2006
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Modulators, channel converters, etc.

I'd recommend taking the audio/video out of each receiver and running it to its own RF modulator (preferably each directly outputting its own channel)

Set the modulators to use every other channel to minimize adjacent channel RF interference and use very good quad shielded RG6 for all runs to prevent local off-air channel interference.

Baseband A/V is just the output A/V from your receivers.

(you can choose whatever channel numbers you want and replace those in my example)

The "Box" denotes one RF modulator output derived from one receiver's A/V outputs

So box 1 would output Ch 2
Box 2 Ch 4
Box 3 Ch 6
Box 4 Ch 8
Box 5 Ch 10
Box 6 Ch 12
Box 7 Ch 14 (UHF)
Box 8 Ch 16 (UHF)
Box 9 Ch 18 (UHF)

You could use the 12 ch combiner with 3 terminators on the 3 unused inputs, or use Qty (3) 1:4 splitters in reverse. Splitters and combiners can be used in reverse just as well.

Here's how to hook up 3 1:4 splitters to do what you want (you can add more to expand further if needed):

Now use several splitters in reverse:
(Boxes 1-4 into Splitter #1 outputs 1-4)
(Boxes 5-8 into Splitter #2 outputs 1-4)
(Splitter #1 input, Splitter #2 input, Box 9 to Splitter #3 outputs 1-3)
Splitter #3 output #4 75 ohm terminator

Splitter #3 input is all of the channels combined. A line amp goes here if you need to go a long way (but watch for excessive level on the input)

I'd say if you need to go <100 ft and to 3 TVs or less, no line amp is needed.

From here you run RG6 and splitters to your TVs.
 
M

mikekohl

Prehistoric Satellite Guru
Supporting Founder
Jun 4, 2004
818
203
Montfort, Wisconsin
Certain low end UHF modulators do not have a very high RF output level.
Many of them struggle to get a +6 dBm output level. If you were to combine four of those together, and use a conventional mixer, you would be mixing them at a very low level (less than 0 dBm), which results in an excessive amount of noise. The poor man's solution would be to back-feed a 4 way splitter; your signals would still be down close to the 0 dBm level, but adding a cheap 20-25 dB distribution amp such as the Pico TA-25 can bring the output level to something acceptable to the eye of a hobbyist. (We don't need a lecture about this from Mr. Krapola....there's the correct way to do things, and there's the "battlefield" way. Some situations have to rely upon field tactics and limited resources to get the job done).

The better solution would be to use more costly modulators with a decent output level, and avoid these problems. Certain mid-priced units have 2 or 3 UHF or cable channels (UHF typically chs 14 to 83, cable band ch 65-139), and not only have an output in the +20 dBm area, but are already combined. You might find this to your liking.

Since I don't have cable here, I tried a completely different approach.
All in-house TV signals are modulated on Cable Channels with low end commercial modulators, using cable channels 14-16-18-20-22-24-26-28-30-32-34.
Any local VHF signals still come in on channels 2 to 13, and the UHF band can still be used for cable channels 65-125 (UHF 14-69). In a pinch, I could use one of those cheapo UHF modulators to sneak some channels in above UHF -69, and use a cable converter to tune them in between 126 and 139. This may get you into frequencies with interference from local cell phones. Try an old UHF tuner than still goes up to channel 83, and listen!

Summarizing the last paragraph, it allows me the ability to distribute just about everything on one wire, with frequencies available to stack other things.
Most electronic TV tuners have enough play in them to tune in local analog off air channels on a cable frequency. Our local Ch 15 = Cable 66
That would put Minneapolis 17 on cable 68
23 is cable 74 29 is cable 80 (examples).

Any other questions?
 
D

dish_in_the_sky

SatelliteGuys Family
May 18, 2006
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You got it...

However, you'll be annoyed if the AC power dips at times, as you'll have 9 (!) of these to reset to the proper channel.

Get a small computer UPS to save you from the short dips...
 
cablewithaview

cablewithaview

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Apr 18, 2005
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any standard 2,3,4,8 or even 16 port splitter can be used for a mixer, when mixing you need to insert the adjacent channel apart from each other instead of like ch.2, 3, 4, etc. this would be installed backwards. I have seen cable taps turned backwards and used for mixing as well. I would recommend a combiner though but this is a home project and may not be needed but that depends on the number of video sources you want to send out through the house.. de mods are for your off airs mainly. if you have a video source with no video/audio output but has ch. 3 & 4 out, then an agile processor could be the way to go. You can always set the processor input to the channel you want to recive (VHF or UHF) and set it to the channel you want to put it out on. remember something though, you need something to at least measure the rf output once mixed. There are some little cheap 45 db gain mods floating around and would be more than enough in your house. turn everything down -3db from full gain, and then go from there. I would recommend a mod with a saw filter, that's my personnel preference though. micro mods if I'm correct are 45 db out and the Trunkline Millennium 95-TMAM is 60db. with the micros, you have to have the chassis, power supply and then the demods, remods, and processors that you need. in other words that is many more parts to work on and trace out if something goes wrong.
 
M

mikekohl

Prehistoric Satellite Guru
Supporting Founder
Jun 4, 2004
818
203
Montfort, Wisconsin
It depends whether his TV tuners default to Cable or Broadcast mode after a power loss. That might mean a UPS for every TV as a solution for worst-case. Fortunately I don't have 9 outlets here, and fairly reliable power, plus practice at pressing the remote control to the Tv/Cable mode after this happens!
 
M

Mr Tony

Thread Starter
SatelliteGuys Pro
Supporting Founder
Nov 17, 2003
326
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Mankato, MN
The better solution would be to use more costly modulators with a decent output level, and avoid these problems. Certain mid-priced units have 2 or 3 UHF or cable channels (UHF typically chs 14 to 83, cable band ch 65-139), and not only have an output in the +20 dBm area, but are already combined. You might find this to your liking
I have one of these already. Its a 2 channel a/v output with a coax ant/cable input and 5 outputs. ChannelPlus 3025 I think. I know about the cable/antenna conversion :D
My TV's default to antenna with a power outage, but since I normally keep it on there no biggie
 
M

Mr Tony

Thread Starter
SatelliteGuys Pro
Supporting Founder
Nov 17, 2003
326
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Mankato, MN
Like I say it was just a crazy idea. Maybe I'll just try the Channel+ unit and the Radio shack distribution amp I have (I have a distribution box that accepts 3 coax and converts them to channels 15-20 and 60-69 for the other 2. If I mix them toghether, it might work :)
 
D

dish_in_the_sky

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May 18, 2006
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It's always fun to work with stuff on hand...

And usually cheaper too :) :D
 
Tron

Tron

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May 6, 2005
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Iceberg said:
so what you're saying is get some of those consumer modulators (lets say 4 or 5 of them)
http://www.sadoun.com/Sat/Products/S/high-performance-125-channel-rf-modulator.htm

and put them on different channels (14, 16, 18, etc) and the output of those go into those 12 channel combiners?
That should work well if the modulators put out enough signal. I haven't priced the consumer level modulators, but the pro CATV ones can be somewhat expensive (especially if they're agile, meaning they can be assigned to whatever channel you want them to be assigned to). You can find pro fixed channel modulators (such as the Blonder Tongue MICMs) cheaper, but the unit you linked to looks like it is an agile modulator which will work well for what you want to do if it puts out enough signal for your combiner. The passive combiners are not that expensive. I picked up a Blonder-Tongue unit that combines 12 RF inputs for around $30.

Hotels use systems like these to combine and distribute their OTA, satellite, and sometimes DVD video on assigned channels to each of the rooms.
 
Last edited:
kstuart

kstuart

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Nov 5, 2006
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Northern California
Reviving this thread to preserve the good information and discussion...

I need to use an RF modulator to route my FTA receivers' output to other rooms. In the past, I used a wireless transmitter, but when I dug that out of storage, I discovered that it used the same 2.4ghz bandwidth as my more recently installed WiFi router (turning on the video transmitter caused the previously stable WiFi to start having frequent interruptions - even using theoretically non-overlapping channels did not help).

So, I'd like to use one of the inexpensive modulators linked in this thread (from Sadoun, among others). But, they never mention if the RF output is stereo which requires use of very recent cheap MTS stereo modulator chips.

Anyone know which inexpensive modulators have stereo RF output?

Thanks!
 
Anole

Anole

SatelliteGuys Master
Sep 22, 2005
11,819
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L.A., Calif.
Look on the back panel picture Sadoun posted above.
It's got stereo input.
I have some very similar units I got a few years ago from Radio Shack.
They've since discontinued them, leaving the item harder to find.

As for 2.4ghz, the interference potential with WiFi, is the reason I have only 900mhz (digital spread-spectrum) cordless phones in my house.
Just a damned good thing the 1kw microwave doesn't leak!
All these things are on 2.4ghz, as is your cell phone's bluetooth.
Can you say band-overload? :eek:
 
kstuart

kstuart

SatelliteGuys Master
Nov 5, 2006
5,206
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Northern California
Look on the back panel picture Sadoun posted above.
It's got stereo input.
Unfortunately, modulators that only put mono sound into the RF feed, have stereo inputs for "convenience".
So, I'm looking for feedback from users that they get MTS stereo on the RF output of a particular unit...
 
S

sbrown1357

Active SatelliteGuys Member
Mar 10, 2005
19
0
Wichita Falls, Texas
So if you want to create a mini home CATV network of 12 channels, you will need Qty 12x Modulators, and Qty 1x 12-way-Combiner

would the single-channel modulator C180 at each reciever hooked up to PHC-12G
pico macom 12 channel 1ghz broadband passive headend combiner work to put all recievers outputs down one coax cable?
thanks scotty
 
Krapola

Krapola

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Jan 10, 2006
214
0
Fairfield, Cali
So if you want to create a mini home CATV network of 12 channels, you will need Qty 12x Modulators, and Qty 1x 12-way-Combiner

would the single-channel modulator C180 at each reciever hooked up to PHC-12G
pico macom 12 channel 1ghz broadband passive headend combiner work to put all recievers outputs down one coax cable?
thanks scotty

Specs...
http://www.picomacom.com/specs/pico/A/A63-A64.pdf
 
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