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Old 2014-01-13, 09:11 PM   #1
HDTV101
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Question RF Modulator For DTV Broadcasting?

Here's how to build your own ATSC digital pirate station on the cheap !

This little box from from China does it all for under $500 ... just add a linear amp and antenna.

http://www.alibaba.com/product-gs/90...modulator.html



RF out in the frequency range of 30~960MHz.

Digital output formats;

DVB-T
DVB-C
DMB-T
ATSC-T
ISDB-T standard TV,
DVB-T
DVB-C
DMB-T
ISDB-T STB
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Old 2014-01-14, 02:18 AM   #2
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I wish there were some better specifications I could look at.

The idea of this product is just like the simple old idea that you could take your old VCR, set the coax output to either Channel 3 or 4, and then run it into a commonly available VHF-LO signal amplifier to an antenna and thus have your own Channel 3 or 4 analogue NTSC TV station running at an ERP of a couple of hundred or even a thousand watts until the authorites shut you down.

Here's why I would never use something like the modulator HDTV101 mentions except inside a Faraday Cage for testing:
  1. Not CSA or UL approved (no insurance company will ever pay off damages caused by it)
  2. Even if the output power of this device is quite low, you still need to run it through an amplifier and antenna, but both of those would have signal multiplication factors that would easily make your broadcasts as noticeable as a screaming baby to the authorities
  3. You would need to inject PSIP data for ATSC tuners to be able to lock onto your signal - I cannot tell if this unit does that
  4. This is the obvious one: 100% illegal for OTA broadcasting
Sorry to have to be such a buzzkill.

Last edited by stampeder; 2014-01-14 at 03:26 AM.
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Old 2014-01-14, 02:56 AM   #3
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It could be used legally in a building's MATV system. Perhaps to broadcast a lobby cam. You'd obviously need to ensure none of the unit's signal is sent out over your antenna array or a channel that's in use, but that's easy enough to do.
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Old 2014-01-14, 03:08 AM   #4
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True, that's the sort of situation that this box is made for, although a good Linux PC with Zoneminder is a much better option for providing real time CCTV monitoring to tenants and security staff.

As for OTA broadcasting, there are a lot of problems that would zap an experimenter pretty hard for using this Chinese DTV box.
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Old 2014-01-14, 06:23 AM   #5
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the bonehead in Toronto doesn't care, why should anyone else?
Not exactly setting a good example there.
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Old 2014-01-14, 12:02 PM   #6
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Another way to transmit ATSC is to use a software-defined radio board such as a BladeRF or USRP B200 (or the upcoming HackRF, which will be even cheaper) together with the open source software package GNU Radio. I put together a transmitter that takes an MPEG transport stream as input and transmits an 8-VSB signal on the frequency of your choice:

http://nuand.com/forums/viewtopic.php?f=8&t=3503

I haven't done much with it yet, but my intention is to use it on amateur radio frequencies. I've been testing it on the 70cm band with a down-converter on my TV to bring it down to channel 3. I used ffmpeg to generate transport streams, mpeg2transports (http://mpeg2transports.sourceforge.net/) to generate PSIP, and a few lines of Python code to multiplex multiple channels and PSIP into a single transport stream.

73,
Clayton VE3IRR
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Old 2014-01-14, 03:19 PM   #7
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argilo that is awesome work you are doing with your 70cm band gear!

I've just opened up the following thread called DIY Amateur DTV: Antennas, Gear, Software over in the Antenna R&D Forum:

http://www.digitalhome.ca/forum/showthread.php?t=197921

Last edited by stampeder; 2014-01-14 at 03:38 PM.
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Old 2014-01-14, 08:06 PM   #8
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Quote:
Originally Posted by stampeder View Post

Here's why I would never use something like the modulator HDTV101 mentions except inside a Faraday Cage for testing
The point of my post was how to build a pirate station on the cheap. A pirate station is anything but legal and if they interfere with legit broadcasts they don't care... like the kid in Ottawa.

The Chinese box is designed for a CCTV system as commonly used in hotels for the Marriott channel. The device must provided basic PSIP data for it to work at all... so yes it must. It seems to be capable of many other global formats too besides ATSC. Its RF output is low but it could always be amplified. Use some LMR-600 to wire it up to a resonant antenna up on a 50 foot tower and you would achieve some significant gain that way too.

They have an even nicer model here: http://www.alibaba.com/product-gs/86...G_4_HD_to.html


It also come with a Chinese Government certified letter of conformity ... So it must be good :-)

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Old 2014-01-14, 08:17 PM   #9
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Quote:
Originally Posted by argilo View Post
Another way to transmit ATSC is to use a software-defined radio board such as a BladeRF or USRP
Clayton,

Yes I love the capabilities of what we can be done with SDR. Endless possibilities.

Very kool setup using 70cm.
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Old 2014-01-14, 09:18 PM   #10
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Quote:
Not CSA or UL approved (no insurance company will ever pay off damages caused by it)
Since it's not AC powered, that's not an issue. However, the 12V adapter will have to be approved as usual. That was one of the driving factors for those "wall warts".

Quote:
This is the obvious one: 100% illegal for OTA broadcasting
As mentioned above, it is legal for amateur radio use, as equipment used in that service does not require IC approval. However, "broadcasting" in amateur radio bands isn't legal either. Other than testing, it's supposed to be 2 way communications.
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