[hilarious01]

Hello,

Excuse me if this is a stupid question but nonetheless need the info. I am an engineer and planning to build a new computer acting as a multi input multi output receiver. I hope on making my life easier by outputting to the TV monitors by using a single coax cable out and splitting it to all the tv's both sd and hd. Now as far as writing code I can do, but I'm still a baby as far as AV, so can my computer act as an HD modulator with multiple channels via software or do I need to get some extra hardware to do this other than a coax output for the computer. Also, does the signal need to be amplified depending on how much the signal is being split? I plan to probably have 3-5 tv's for the football season. I figured rather than having a bunch of HDMI, RCA, and coax outputs that this can work.


Another thing, are there coax cable relays? I'm thinking of using a switch on my software so passively the directv receivers go to the tv's and when relay switch is active it uses the coax signal from the computer

 

[AntAltMike]

Toner Cable is now selling an HD modulator that can take two component HD inputs and modulate them to one RF QAM channel. It wholesales for a little under $7,000. I recently spoke to someone who is using one in a commercial environment and it seems to be working OK for him.

 

[ctdish]

This might be cheaper if it is available. http://www.zeevee.com/connected-home/zvbox150

http://www.amazon.com/gp/product/B00...SIN=B0018L7NUA

John

 

[hilarious01]

Much appreciated, does anyone know if this can be duplicated on a PC so rather than having to buy multiple ZV boxes (which can add up to be a lot) for the multiple video feeds if I can simply do this on a pc with a coax connector? or am I just have to get a bunch of different connectors on my computer?

 

[duvetyne]



Quote:
does anyone know if this can be duplicated on a PC so rather than having to buy multiple ZV boxes

No, you need a modulator.


What kind of engineer are you?

 

[hilarious01]

AE, and finished off in EE as well. Well, I guess I want to get into the nitty gritty and find out how it's actually done. How does a HD modulator work, theoretically (the process) and technically, and why can't it be duplicated digitally via code, or what extra hardware or components would be needed to duplicate it as to be as close as possible to be an extension of the pc. If push comes to shove I'll read up on it more and tear one open, not the first time I've done it and definitely not the last time.


Thanks for the help


Also, does anyone know if there is a coax cable relay so to make a few simple logic circuits

 

[k_ross]

Sounds like you should look into software-defined radio.

 

[dr1394]



Quote:
Originally Posted by hilarious01 /forum/post/16878787


AE, and finished off in EE as well. Well, I guess I want to get into the nitty gritty and find out how it's actually done. How does a HD modulator work, theoretically (the process) and technically, and why can't it be duplicated digitally via code, or what extra hardware or components would be needed to duplicate it as to be as close as possible to be an extension of the pc. If push comes to shove I'll read up on it more and tear one open, not the first time I've done it and definitely not the last time.


Thanks for the help


Also, does anyone know if there is a coax cable relay so to make a few simple logic circuits

A QAM modulator that actually transmits a carrier on a specific TV channel is a pretty big project.


The QAM generator itself can be done in an FPGA, and there are some ASIC chips on the market. The Broadcom BCM3034 is a single channel device and there's also the BroadLogic TeraQAM BL85000 which does 32 channels in one chip.


The BCM3034 is nice because it has an on-chip D/A, which is another part of the design. You can generate the digital QAM signal with an FPGA (or some software defined gadget), but you still have to convert to analog with a D/A. And not just any D/A, but an RF D/A that outputs an IF (Intermediate Frequency) signal (usually at 44 MHz).


After the D/A, you need to heterodyne to the desired RF channel. The mixer stage is pretty easy, but the local oscillator is a bit of a problem. If you want frequency agility (that is, you can program the unit to any RF channel), then you need some kind of VFO (Variable Frequency Oscillator). These days, that's usually done with a DDS (Direct Digital Synthesizer). But a DDS is a whole sub-system in itself. However, if you can live with each unit being customized to a single RF channel, you can use a crystal oscillator instead.


After the mixer, you have to generate a little bit of power with some kind of RF amplifier. Now we're getting into hard-core analog stuff. Discrete transistors and lot's of inductors and capacitors. In addition, if you want to be able to pack the channels without any empty channels in between, then you'll need to properly filter the RF waveform to properly fit in the channel.


The ZeeVee ZvBox 150 thing looks like the solution you (and everyone else that asks about modulators) want. I wonder how much they cost?


Ron

 

[dr1394]

Looks like it's a kilobuck.

http://www.copperbox.com/Digital-modulators-s/792.htm


Ron

 

[sneals2000]

In Europe - someone's managed to create a VHF DVB-T digital signal using a VGA video card - utilising the harmonics of the VGA device.


However it is a non-real time implementation that just carries a static image :

http://bellard.org/dvbt/


Probably not relevant - but interesting none-the-less.


Also these may be of interest :

http://www.computermodules.com/usb-t...Modulator.html


(Though they require MPEG2 encoding separately)

 

[SteveBagley]



Quote:
Originally Posted by sneals2000 /forum/post/16879950


In Europe - someone's managed to create a VHF DVB-T digital signal using a VGA video card - utilising the harmonics of the VGA device.

Auntie has gone one better than that producing proper TV channels out of the back of commodity PC hardware. Details in this blog post http://www.bbc.co.uk/blogs/pressred/...gital-tv.shtml


Steven

 

[hilarious01]

Thanks a lot, I didn't expect this to be an easy project and I figured it would take me a while to complete but part of the reason I wanted to do it is for the experience. You've all been really helpful in pointing me in the right direction and it is much appreciated.

 

[matthd1]

Hi everyone,

i leave in London and i've got new DVB-T TVs around my house.

Unfortunately all services are SD at the moment, and only my satellite HD set top box has hd programs.

Is there any simple and cost effective solution to convert component hd to RF DVBT so i can distribute my HD video to all my TVs easy ?

I've googled around and found PRO VIDEO INSTRUMENTS COM site that seems to offer this kind of Video to RF DVBT boxes.

Has anyone an idea about the pricing of their VECOAX-T1 HD MODULATOR ?

Any other suggestion without running new cables around ?

I have 7 TVs !

Thanks a lot for any suggestion

Matt

 

[Glimmie]



Quote:
Originally Posted by dr1394 /forum/post/16879422


A QAM modulator that actually transmits a carrier on a specific TV channel is a pretty big project.


The QAM generator itself can be done in an FPGA, and there are some ASIC chips on the market. The Broadcom BCM3034 is a single channel device and there's also the BroadLogic TeraQAM BL85000 which does 32 channels in one chip.


The BCM3034 is nice because it has an on-chip D/A, which is another part of the design. You can generate the digital QAM signal with an FPGA (or some software defined gadget), but you still have to convert to analog with a D/A. And not just any D/A, but an RF D/A that outputs an IF (Intermediate Frequency) signal (usually at 44 MHz).


After the D/A, you need to heterodyne to the desired RF channel. The mixer stage is pretty easy, but the local oscillator is a bit of a problem. If you want frequency agility (that is, you can program the unit to any RF channel), then you need some kind of VFO (Variable Frequency Oscillator). These days, that's usually done with a DDS (Direct Digital Synthesizer). But a DDS is a whole sub-system in itself. However, if you can live with each unit being customized to a single RF channel, you can use a crystal oscillator instead.


After the mixer, you have to generate a little bit of power with some kind of RF amplifier. Now we're getting into hard-core analog stuff. Discrete transistors and lot's of inductors and capacitors. In addition, if you want to be able to pack the channels without any empty channels in between, then you'll need to properly filter the RF waveform to properly fit in the channel.


The ZeeVee ZvBox 150 thing looks like the solution you (and everyone else that asks about modulators) want. I wonder how much they cost?


Ron

And once he gets this all done where does the video to be displayed come from? The ATSC standard is MPEG2 which could come from the PC as a pre-compressed file. If realtime analog video, he will need an MPEG2 encoder. Doable in commodity PC software but not real time.

 

[sneals2000]



Quote:
Originally Posted by Glimmie /forum/post/20690983


And once he gets this all done where does the video to be displayed come from? The ATSC standard is MPEG2 which could come from the PC as a pre-compressed file. If realtime analog video, he will need an MPEG2 encoder. Doable in commodity PC software but not real time.

Real time MPEG2, for SD at least, encoding is do-able in software these days isn't it? ISTR that there are a number of cheap analogue TV capture cards that have "software MPEG" encoding for Media Center these days aren't there?


Originally Media Center analogue capture required a PCI/USB solution with an onboard hardware MPEG2 encoder (Hauppauge PVR 150 for instance), but more recently it has been possible to offload the MPEG2 encoding (for SD at least) to the CPU I believe - with drivers 'pretending' to be hardware MPEG2 encoders - allowing cheaper SD analogue capture within Media Center? (Not that anyone really bothers with SD analogue capture in 7MC I suspect)