1. RB-TV on the BATC DTX1 Convention for Amateur Television 2015 (CAT15)
over the weekend of 5th and 6th of September
at Finningley Amateur Radio Club.
A presentation by Laurence M0LDZ.

2. Integrated MPEG2 encoder & RB
The DTX1 accept PAL or NTSC Analogue Video and Stereo Sound, and convert this to Transport Stream.
First, the video signal is fed to an ADC chip, which produces an 8 bit output at 27M Bytes/Sec.
We compress this signal using an MPEG2 Encoder chip – but below 1Mb/s it’s unusable. How do we get round this problem for RB-TV?
A similar process is applied to the audio channels and the two feeds are merged. This adds to the bandwidth generated by the video.

3. MPEG Compression Chip
MB86391

4. Digital Modulation – the Hard Bit
We add control packets to the audio and video - now we have a transport stream, but this is not yet encoded as per DVB-S Standard, which is very complicated.
The solution – a Field Programmable Gate Array (FPGA) takes the transport stream and encodes the signal to the DVB-S standard, producing digital Quadrature outputs.

5. Complete DTX1 Board

6. A Subtle Feature Exploited
The DTX1 is a variant of a Antennair’s DVB-T product. This was designed with a 2nd video/audio encoder stage option – so the FPGA contains a 2 Channel Multiplexer, and the PCB brings out the spare input channel on a 34 Way connector. (Was pins, but is a socket on DTX1).
This left open the possibility of future add-on card with different compression e.g. H.264
Since the Raspberry Pi board has a camera input and H.264 Compression in Hardware, we decided to make a Transport Stream Dock PCB!

7. Original TS_Dock Schematic

8. Early Issue with TS_Dock PCB

9. New TS_Dock PCB and the RPi

10. Wide Range Digital Synth
ADF4350 – to 4400 MHz

11. Analog Devices Modulator
ADL5375

12. Ongoing Work on DTX1 Frequency Range
Removing the Harmonic Filter on the Synth Output – allows useful signal output to 2.45GHz with re-programming (output is down ~7dB)
Harmonics at lower frequencies slightly worse but close-in performance is still excellent. External filters should be used.
Re-programming the Synthesiser at the low end already extends coverage down to 2 metre band, despite modulator IC’s quoted lower limit!
Beta release firmware available NOW at CAT15.

13. Thanks and Acknowledgements
Hardware design of TS_Dock PCB by yours truly - Laurence, M0LDZ
DTX1 Firmware design by Carl M0ICS
Raspberry Pi firmware for sending the H.264 Stream on to the TS_Dock parallel port by Evariste, F5OEO
Testing above 2GHz by Noel G8GTZ.
All those here today & online for watching!

14. A Compact Solution for RB DATV
BATC DTX1 Encoder / Modulator