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ATTiny85 does NTSC over VHF

Transmit video without extra components.

cnlohrCNLohr
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I took an ATTiny85 and abused its hardware to do real-time AM modulation of an NTSC signal into VHF then send it over to a TV.

Check it out on github: https://github.com/cnlohr/avr_vhf
And check it out on youtube: http://youtu.be/DJyQi0aUqVQ

I mention in the video closed captioning being possible. I want to make it clear that I do not intend to make this happen unless I find the original remote. It would be several hours for me to try to get my AVR with IR LED to do all the menus and everything to get closed captioning on :(

  • 1 × ATTiny85 Dev Board Any ATTiny85 board with an ISP header
  • 1 × AVR Programmer
  • 1 × Analog TV with Analog Tuner

  • 1
    Step 1

    Get an ATTiny85 Devboard (or use mine) https://oshpark.com/shared_projects/ZDUBhs9S And an AVR Programmer

  • 2
    Step 2

    Check out a copy of avr_vhf from here: https://github.com/cnlohr/avr_vhf

  • 3
    Step 3

    Plug two wires into PB3 and PB4 of your AVR, PB3 should be shorter than PB4. I've typically made them about 2 feet long. I don't know enough about RF to know the correct length for them, maybe 614mm? The other one I made about 9 inches shorter.

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Discussions

SuperCrackMunkey wrote 12/19/2015 at 00:34 • point

Could this be modified to take an input low resolution NTSC signal and transmit it over AM? 

  Are you sure? yes | no

icanhazadd wrote 02/26/2015 at 17:58 • point

Analog Channel 3 in the US is 60Mhz, so basically both sides of your antenna should be about 8' long for a full wavelength antenna. You might find you have to trim back a few inches per side (nearby objects like powerlines in the walls etc will detune your antenna a bit) If your antenna is currently about 2' on each side then you've got an 1/8 wavelength diapole antenna. you'll have best results with full wavelength. Also the sides should be even.

  Are you sure? yes | no

CNLohr wrote 02/27/2015 at 05:21 • point

Sides should not be even.  Otherwise the black/white/sync levels will be out-of-kilter.  I've found that making one much shorter nerfs the signal to make up the extra distance for the white.

  Are you sure? yes | no

Brian wrote 12/20/2015 at 23:19 • point

The sides should be even as icanhazadd said. If you change the symmetry of your dipole and get a better picture it means you are changing the loading on your transmitter and it's frequency is changing slightly. If the sync frequency is off the white / black contrast won't be good. 

You could just as easily connect one of the wires to earth ground and then adjust your oscillator frequency as necessary to get the best picture.

  Are you sure? yes | no

icanhazadd wrote 02/26/2015 at 17:48 • point

Antenna resonance: 492/Freq(Mhz)

  Are you sure? yes | no

Benchoff wrote 02/26/2015 at 04:52 • point

I'm trying to convince the overlords to fund a Hackaday Baltimore meetup. I'll bring down an old TV when that happens.

  Are you sure? yes | no

CNLohr wrote 02/27/2015 at 05:22 • point

Unless there is something absolutely critical if there's a hackaday meet up any less than 5 hours from Baltimore, I'm gonna be there.

  Are you sure? yes | no

Benchoff wrote 02/27/2015 at 15:40 • point

Well, we're going to this for sure: http://www.vintage.org/2015/east/. Bit of a hike for you, and it's in new jersey.

But we're doing three events for the hackaday prize this year. That's NYC and either LA or SFO. I'm pushing for Baltimore for the third one.

  Are you sure? yes | no

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