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Broadcasting on VHF — Parallax Forums

Broadcasting on VHF

rwgast_logicdesignrwgast_logicdesign Posts: 1,464
edited 2012-12-13 13:06 in Propeller 1
Ok so a while ago I did this fairly simple tutorial at gadget gangster showing you how to use the TV driver to brodcast video. Today I picked up some sony watchman portable TV (black and white :/ but you cant beat 2 dollars) I got it specifically to use for a wireless screen for my robot, I figured it would be cool to be able to see graphical representations of the lidar/sonar and read statistics like speed.

Anyways I dont know anything about RF, at the end of the tutorial at GG it says you can brodcast and revive data on the video generators. Im curious what kind of bandwith could you get doing this? Would this be a good way to do wireless serial, Im sure with some antennas you could get good range, maybe 50ft or so? Could you brodcast video and data at the same time maybe of different channels? What is the legality of this?

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-12-12 14:47
    This question comes up from time to time, and a lot has already been said about it:

    -Phil
  • Mike GreenMike Green Posts: 23,101
    edited 2012-12-12 15:33
    If you have to ask, you probably don't know enough to make it work. The fact that its theoretically possible to broadcast video and audio and maybe some data doesn't mean that it's practical or a good way to do anything. As has been mentioned before many times, the quality of the signal produced by the Propeller this way is awful and can't be made legal without a whole bunch of external hardware which sort of defeats the purpose of the whole thing. I've gotten a range of maybe a foot or two with broadcast video out, a proper dipole antenna, and a little portable TV. The display was very noisy ... barely readable.
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-12-12 16:29
    Oh ok thank you for the links phil. I will look go over them with a fine tooth and comb before deciding to peruse this any further.

    Maybe im confused I thought that book programming and customizing the propeller had something in it about wirelessly broadcasting to a TV. The more I look at some of these projects online they are just sending data via an xbee or some other means from a propeller to a propeller actually connected to a TV which then does the rendering. Is this the same technique used in the book mentioned above? I had hooked this all up before, with a regular TV, and got a decent signal just using wires for antennas and thought it could be a whole bunch better with decent antennas, sad this isnt this case. Acually broadcasting wireless TV from a robot would be pretty cool.
  • Mike GreenMike Green Posts: 23,101
    edited 2012-12-12 17:29
    Yes, broadcasting wireless TV from a robot is really neat, but you won't see any units on the market that use the actual analog TV channels. Those are not available for use anymore and only used TVs will be capable of receiving them. Some of the R/C equipment manufacturers make nice wireless transmitters that work on specific frequencies. Most popular is the 2.4GHz band used by WiFi. These output video and sometimes audio as well. The matching transmitters accept standard video and you can use the Propeller to overlay readable data on the picture being transmitted. The Propeller Backpack is already set up for that and includes an overlay video driver (see the product page).

    You can always use an xBee or WiFly module to transmit the data to a computer to overlay on a video feed. A data channel like that could handle a series of still images or low resolution video, but you need a video transmitter to send full resolution full speed images in real time.
  • TubularTubular Posts: 4,703
    edited 2012-12-12 19:51
    I think the easy way is to use a commercial composite video transmitter. However you can use something like Phil's Propeller Backpack to overlay information from the propeller onto that live video feed.
  • Mike GMike G Posts: 2,702
    edited 2012-12-13 13:06
    What about a Wireless IP security camera? The cameras are cheap and easy to use. This one has been in operation for almost 2 years watching a Spinneret; http://www.agaverobotics.com/spinneret/controlpanel.htm. Before that I had the same camera focused on an interactive robotic arm. Users could control the arm remotely over the Internet from anywhere in the world.
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