Tuesday, July 29, 2008

Mission: Mobile pirate TV station on the cheap

I've always wanted to get a pirate radio or tv station going. Throw on some tapes of b scifi and horror, maybe a bit of televangelist-style banter in between. OK, maybe it would be best if I wasn't the only one doing the programming. Anyway, from my understanding this is what you need to do it up (a lot of this can be found by the curb or at thrift stores):

Basic Equipment:
Video sources: cameras, vcrs and dvd players are the options that spring to mind. My new favourite vcr is a portable hitachi (model vt-8a) that records in stereo, dubs over audio or video, and has a footprint of maybe a foot square. All that for six bucks! They have a very similar one at the same thrift shop designed for playback only, but you can't go wrong at that price (assuming it works of course).

RF modulator: something that changes the source video signal into a radio signal that can travel over the airwaves. Most vcrs can put out a signal on channel 3 or 4 (VHF), and there are stand-alone devices that do the same thing (say if you want to watch dvds on an old tv without a/v inputs.) When I last checked you could get these for around $15 or so.
For this purpose I am thinking to use a "daveco video sender" that I have around somewhere (need to find that again.) It looks like it was made in the 1980's or so and as far as I can tell it sat on the shelf of the radio shack until I picked it up last year. It takes a composite video signal (the yellow connector) and one channel of audio (oh well), and it puts out a signal on channel 14-17 (UHF) over an antenna (you set which channel using a screwdriver and can even pick something in between if you want!) I couldn't find much on these devices on the internet, so at the time I figured its rarity value warranted shelling out 50 bucks for the thing. I like the idea of a UHF station better anyway: I figure channel 3 or 4 is likely to have something on it already, but 14 is probably pretty safe.

RF (wideband) amplifier: Chances are your modulator is not putting out a very strong signal, so you want to amplify it before sending it to an antenna. You need an amplifier designed for this purpose (a radio frequency or "wideband" amp); from what I gather audio amplifiers are similar in general principle but they are meant to work with much lower frequencies. They sell these new at places like radio shack (I think for about $40+) but they don't seem to be very common in the wild from what I've seen.
A VCR will amplify antenna signals too, not sure if you could get too much range this way though.
I have an "Archer amplified TV/Video selector", part #15-1262, which I think cost me $5 (the shop owner asked 10 but I buy enough of his crap at asking price). It has five coax inputs, three outs, and a dial corresponding to each output to select from the 5 sources. I am thinking it might be best to use it as an amp instead of as a switch, since most of my gear uses rca a/v cables, not coaxial.

Antenna: I don't know too much about antennas but I would guess that an antenna that picks up tv channels in the appropriate range (i.e. VHF [2-13] or UHF [14-?]) will work adequately. Obviously some more research and experimentation here would be helpful. My feeling is the bigger the better. Placement is something to think about too; a high spot is probably a good idea.

Cables: You'll need a bunch of rca type a/v cables to connect everything together. Female to dual male rca adapters would come in handy for splitting signals (e.g. from the vcr to both the monitor and the rf modulator, so you can broadcast and watch at the same time.)

Mobile power source: Probably a lot of your gear will be designed to run off house current (AC). You can get power inverters designed for car use (12V) at pawn shops for around $10 sometimes. I don't have a car, so I am thinking a battery designed for a motorcycle or similar might work best for portability. I think I might have one around somewhere but I haven't tested it. Chargers for car batteries or similar are pretty easy to find used too, think I've seen them for about $10 as well. A power bar bar would be handy too.

Video monitors: It's hard to imagine running a tv station without at least one monitor to see what you're sending out. I guess you could go fancy and get little lcd monitors but I'm cheap. You can get inexpensive 5" b+w tv's at thrift stores ($10-15 is common.) These come under different labels (including Curtis, Sylvania) but most of the recent ones have identical cases and minor feature differences. The only thing you really have to look out for is a/v inputs, some don't have this feature. An extra monitor or two means you can be cuing up up the next clip on a second vcr, but it would be nice to have a slick way of switching which source you send to the modulator.

Video mixers/switches: Some sort of switching device is a big step up from plugging and unplugging cables. I saw an a/v switch at active surplus for about $20 (new) with 3 inputs, I figure that's more or less reasonable. If you're thinking to get a mixer to do some fancy wipes and fades, I'd say don't bother. Most require the two sources you're mixing to be "synchronized" which requires additional expensive equipment, otherwise you will get that weird screen rollover effect when you try to do your fancy star wipes or what have you.

OK, more on this later, I will try to get some pics up too.

Further reading:
http://www.pcs-electronics.com/tvmax-2000-transmitter-p-1224.html: A commercially made tv broadcast setup that sells for 160+ euros (the UHF version is more expensive.) Just putting this up for reference. Apparently with 3 watts of power you can get from a few hundred meters to 5km of range depending on antenna and conditions.

Edit, March 2011: I have now relocated the Daveco device I mentioned so I can get some pics up soon. Probably the simplest way to actually accomplish mobile broadcast would be  to use it with a laptop with S-video out. I have an old PIII Thinkpad with this capability and interestingly it takes about the same input voltage, 16V for the Thinkpad vs 18V for the video sender. At 900 MHz the laptop has enough cpu power to handle xvid decoding at a reasonable enough resolution for the purpose. Overall though I believe it's better not to tempt fate with unlicensed broadcasts, making wifi an attractive alternative.

1 comment:

kate said...

i am going to disagree with you on the programming thing. you MUST be the sole programmer. the world needs this window into your brain.