What is DigiThin?

The place for discussion about the RPi add-on RB-TV modulator card developed by G4EWJ and supported by the BATC Shop
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Location: Wirral

What is DigiThin?

Post by G4EWJ » Mon May 11, 2015 3:59 pm

DigiThin is a narrowband QPSK modulator pcb, which sits on the Raspberry Pi model B 26 pin header. Symbol rates of up to 333k are possible. Bandwidth is roughly 1.5 x symbol rate. RF output is 1mW.

Software by F5OEO running on the RPi takes MPEG-4 video from the RPi camera, converts the data to IQ format and sends it to the DigiThin pcb. An external local oscillator sets the transmit frequency. The modulator chip specification is 100-1000MHz, although G4KLB has had it working on 50MHz and 70MHz.

It can be received using the Tutioune software from F6DZP, with a suitable receiver. Most set top box receivers do not handle such low symbol rates, so a satellite receiver module or a PC satellite receiver card is required.

It is designed for home construction, with no difficult soldering. The chips are SOIC with 1.27mm pin spacing and the other SMD components are at least 1206 size.

It is an experimental project, rather than a finished product and there may well be circuit modifications required as more people build it. The software is likely to change, so a dsPIC33F programmer is necessary.

Partial kits are now in the BATC shop.

For more details, see the article in this BATC magazine: http://www.batc.org.uk/club_stuff/rbtv.pdf

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