Broadcasting the propeller
BillDer
Posts: 33
I remember a few comments here and there that if one attaches a bit of wire to the rca jack one could broadcast your tv signal from the propeller. Is that true? If so has anyone tried? I would like to know. Can I just plug in an rca plug, strip the wire and tune in my nearby tv set and see my handywork???
I would love to experiment with this. Please let me know.
I would love to experiment with this. Please let me know.
Comments
Yes it is true. There are several things to watch for:
The length of the antenna has to be a quarter of the wavelength of the signal
The range is very low. I don't remember how much. But start with only 20 cm
distance between your transmitting and receiving antenna
best regards
Stefan
Look at the comments at the end of TV.spin, in particular tv_mode, tv_pins, and tv_broadcast
You don't need to strip the wire, except where it makes contact at the connector.
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· -- Carl, nn5i@arrl.net
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For me, the past is not over yet.
Forgive me if you already know this, but I suspect from your posts that you might not: You can't just stick a wire into the RCA jack and expect to broadcast a TV signal over the air. As Mike hinted, the TV object has to be configured for broadcast video instead of baseband video, and you have to specify a frequency to broadcast on. You will get the best quality reception on channel 3 (60 MHz), assuming an 80 MHz clock, since the Propeller's PLLs exhibit the least amount of jitter when configured for that channel.
-Phil
Addendum: Attached is a demo program to get you started.
Post Edited (Phil Pilgrim (PhiPi)) : 2/21/2009 11:32:11 PM GMT
I mean, the last British VHF TV transmitters closed down in 1985. I don't recall seeing a TV with VHF since sometime before that, I think it used tubes instead of semiconductors[noparse];)[/noparse]
Is here any way us in Europe can play with this?
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For me, the past is not over yet.
-Phil
When I say everything, the pissy thing is that the cable TV went digital as well. So everyone had to buy a digibox converter not just those with antennas on the roof.
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For me, the past is not over yet.
I can't imagine what advantage there is in forcing cable customers to go digital. Why do the conversion at millions of leaf ends when it could be done once, at the trunk? (Or does Nokia make converter boxes, too?)
-Phil
Strange thing about the coupon program. The USA generally regards it self as capitalist and many Americans chide Europe and especially Scandinavian countries as being overly socialist. Well how come Americans get the free hand out of converter boxes and Scandinavians have to buy their own?
The thing about cable customers being forced to get converter boxes really bugs me. Apparently this is a Finnish thing, over there in Sweden for example it was not so.
I have not heard of Nokia "digiboxes" as they are called around here, most I've seen were made by Samsung.
To bring this slightly back on topic. Has any one been generating FM audio radio signals with the Propeller?
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For me, the past is not over yet.
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· -- Carl, nn5i@arrl.net
When Chip gets his sine wave outputs going in Prop II we are in business perhaps.
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For me, the past is not over yet.
-Phil
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For me, the past is not over yet.
Why not make a cleaner PLL?· Modern comm radios all have very clean PLLs, the technology is mature.· Better still, why use a PLL at all -- if you want to run at 80 MHz, for example, use an 80 MHz crystal.· It's not like you need to tune around looking for someone to talk to.· I've never understood what possible utility there could be in being able to run a processor at slower than rated speed anyway.· If it's to save power, use WAITCNT, WAITPNE·and the like to sleep at low power when not busy.· That doesn't muck up other cogs on the same clock.
On the subject of tank circuits, there are better ways to filter a low-power signal -- filters with much higher Q, much steeper skirts, deeper ultimate rejection, superior in every way.· Easier to use, too.· But the real problem is that a microcomputer is not, and perhaps cannot be, designed to serve as a transmitter.· The cheapest modern transceivers, and the most expensive ones, and the ones in between, all have microcontrollers nowadays.· They control the transmitters, but they're never used themselves to generate the transmitted signal.· No one wants to be a rogue with a dirty signal in today's crowded spectrum.
But maybe we might as well go back to spark.
Zzzzzzzzz zzzzzzzzz zzz zzz zzz······· zzz zzz zzz zzzzzzzzz zzzzzzzzz.
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· -- Carl, nn5i@arrl.net
It's a well-established technique, Carl. Google direct digital synthesizer dither. Properly applied, it's capable of producing signals clean enough for RF work.
That's not the point of my efforts. The point is to see how far I can get with the Propeller. It's called experimenting.
A different subject, but I'll take the bait anyway: For one it helps to keep the higher frequencies off the PCB and internal to the chip, thus making it easier to meet emissions requirements. The Propeller isn't the only micro that does this, BTW.
Don't laugh. That's pretty much what Zigbee and other UWB techniques are all about: digitally-controlled impulse noise.
In all seriousness, the application of digital techniques like UWB and CDMA to RF could well render last century's notion of "spectrum" obsolete. (How's that for provocative?) The only reason we still talk about spectrum in the classical sense is due to regulatory issues and a lingering dependency upon passive tuned circuits. But with emerging high-speed digital technology and software radio techniques, "spectrum" can be extended from the frequency domain to multiple "code" domains. The possibilities are endless.
-Phil
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· -- Carl, nn5i@arrl.net
Phil,
Thanks for posting that code !
I've been looking for "tv transmitter" examples, and your's is the only one I've found so far.
Seems to be nothing in obex either.
I just tried it with a ~3 foot length of wire for an antenna, and it's working.
As expected, the signal is very weak and "snowy", but I'm amazed that it works at all.
Is the "snow", just a result of the very low output power of signal ?
"Theoretically" (heh), if a video amplifier was connected to the prop, would that clear up the picture ?
Or are there other factors in the signal generation besides just more output power required ?
I don't know, maybe the fact that the US is a bit larger than Finland!!!!!
Andy, you do realize that Heater's comment was made seven years ago.