The Portsdown DATV transceiver system

Introduction

The aim of the Portsdown project is to provide a definitive DATV project which offers an easy way to “get on air” at a relatively low cost, cover most of the common modes and involve some basic construction. It will enable an amateur operator with little or no knowledge of Digital ATV to construct the hardware elements, load and configure the software and use the system to send live Digital ATV signals across town on his existing aerials. It will include the new DX RB-TV modes and the ability to receive and transmit to local repeaters using the more traditional 2 and 4 Msymbol DATV modes.

• Symbol rates to include the Reduced Bandwidth (RB-TV) modes and “normal” DATV modes

• Frequency coverage of 146 MHz, 437 Mhz and 23cms

• Cost-effective stand-alone (not PC based) Digital TV Transmit solution

• Flexible receive solution based around readily available software

• Analogue video input to allow use of camcorders and mixing desks

• Use of commonly available components and modules

• Modular construction enabling a step-by-step system build and easy trouble shooting

• Designed to encourage home construction and requiring an average skill level

• Fully documented and supported including easy software installation and upgrades

At the heart of the Portsdown project transmitter is a Raspberry Pi (RPi) computer running a BATC customised version of the F5OEO rpidatv software. The choice of the RPi is primarily due to the fact that it has an on-board MPEG-4 (H264) encoder and the versatile hardware interface (GPIO) capabilities. A touch screen interface on the RPi enables the system to be used without further need to connect up keyboard and mouse. If the LCD is not available, the system can be controlled by keyboard and mouse or using an external PC connected over a wired or wi-fi network. The Portsdown RPi software is capable of controlling the ADF4351 module, currently available for around £20, to give an output for 146 MHz, 437MHz and 23cms.