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Author Topic: Analog TV trasmitter  (Read 2621 times)

Offline gavinmc42

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Analog TV trasmitter
« on: February 07, 2016, 12:04:33 AM »
Just been playing with pifm.
http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry_Pi_Into_an_FM_Transmitter
You can just extract the binary and wav files, works fine.

Was trying to transmit camera pics via wifi, having trouble with making a wifi server.
ie wifi web server controlled robot.

Anyway, had a thought.
Now that we don't have analog TV any more, what to do with those frequencies?
Here in Oz analog TV in the low VHF band was about 46 to 230MHz.
https://en.wikipedia.org/wiki/Australian_and_New_Zealand_television_frequencies.

Anyway, pifm with no sound file is just a carrier frequency.
In Analog TV the video is amplitude modulated.
Use GPIO 4 and the RCA jack and a few resistors and we have a tv transmitter.
Useful for robot vision, home automation output?

Seems too simple, must be something wrong with my logic.


Offline Greg Erskine

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Re: Analog TV trasmitter
« Reply #1 on: February 07, 2016, 01:33:41 AM »
Didn't to government sell those old AM frequencies to the telcos for the modile network?

Offline Greg Erskine

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Re: Analog TV trasmitter
« Reply #2 on: February 07, 2016, 02:17:47 AM »
Didn't to government sell those old AM frequencies to the telcos for the modile network?

Analog TV not AM.

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Offline gavinmc42

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Re: Analog TV transmitter
« Reply #3 on: February 07, 2016, 04:23:26 AM »
Found next version of pifm
http://www.rtl-sdr.com/transmitting-fm-am-ssb-sstv-and-fsq-with-just-a-raspberry-pi/
130KHz to 750MHz

Analog TV low VHF band 45-230MHz.
Ch 0-2 are 46-70Mhz
Ch 3-5 overlap the FM radio bands
Ch 5A-12 are 170-230Mhz

No plans yet for these freqs except digital radio 174-230MHz.
http://acma.gov.au/~/media/Spectrum%20Transformation%20and%20Government/Issue%20for%20comment/pdf/FYSO%202015-19%20pdf.pdf

http://www.acma.gov.au/Industry/Spectrum/Radiocomms-licensing/Apparatus-licences/radiocommunications-services-in-broadcasting-bands

Possible uses are IoT LoRa sensor and data telemetry.
Semtech's SX1276 are 137 to 960 MHz.

Seem to remember someone picked up a Pi transmitting 2000Km away.
So very long range sensor transmitters on 50Mhz?
Probably need a Pi filter to stop harmonics?

The UHF TV bands ch 25-69 500 to 820Mhz  and 400Mhz are going digital.
No idea on other countries analog TV bands.