Tag: TV

SSTV in Max

Slow scan television simulation using Jitter.

See this Cycling 74 forum post for an explanation of how frame rate is limited by audio sample rate and  horizontal resolution: https://cycling74.com/forums/topic/jit-poke-vertical-bars-at-high-scan-frequencies/

Download

https://github.com/tkzic/max-projects

Screen Shot 2015-04-09 at 7.24.11 PM

Folder: sstv

Patches:

  • raster-scan4.maxpat (original)
  • raster-scan5.maxpat (better frame rate by lowering screen resolution to 160 x 120)
  • raster-poly-wrap5.maxpat (even better frame rate – up to 15 fps – by up sampling to 384 KHz)

Note – set your audio sample rate to 96KHz if possible, to get the results described above.

Macbook analog TV mirroring

How to connect a new computer to an old Television

Signal path

Connect a VGA adapter to the Macbook DVI (Thunderbolt) port.

Screen Shot 2015-03-27 at 4.59.58 PM

http://www.amazon.com/Tera-Grand-DisplayPort-Thunderbolt-Microsoft/dp/B006FKTR3U

Connect a VGA cable from the adapter to a PC-to-TV adapter. This converts VGA to video component (RCA plug) output. The sound from the Macbook can go through this adapter as well – it gets passed through to the RF modulator.

Screen Shot 2015-03-27 at 5.02.22 PM

http://www.amazon.com/gp/product/B002PXFJ2O

Connect the PC-to-TV adapter, using RCA cables, to an RF modulator.

01502526_00

http://www.radioshack.com/rf-modulator/1502526.html#.VRXF67qHRbw

Connect a coaxial cable from the modulator to an RF transformer (75 to 300 ohms)

Screen Shot 2015-03-27 at 5.10.10 PM

http://www.radioshack.com/matching-transformer/1501253.html#.VRXHHbqHRbw

Connect the 300 ohm leads of the matching transformer to the antenna input terminals of the TV.

references

 

 

VCR’s are analog TV transmitters

Any VCR with antenna output has a built-in RF modulator.

Generally they transmit on channels 2-4. Here are the US frequencies:

from wikipedia http://en.wikipedia.org/wiki/Television_channel_frequencies

The signal is weak, not intended for broadcast. Not legal to broadcast… but hypothetically, amplifiers and antennas could be connected.

This audio signal is from an iPod playing through a VCR received by rtl-sdr in Max on 65.75 MHz. (channel 3) using a random length wire connected to the antenna output.

 

Notes about RF modulators:

I have tried this with some small RF modulator boxes. One of the problems is that you need to send a signal to the video input, or the modulator won’t run. You can get a rough signal by patching one of the audio channels into the video input jack. Or a better signal by using the video composite output of a raspberry-pi. Although the VCR gives a much cleaner signal