The Portsdown DATV transceiver system

The Portsdown DATV transceiver project provides an easy way to “get on air” with Digital ATV at a relatively low cost covering all of the commonly used DATV modes enabling it to be used for cross town QSOs, accessing ATV repeaters and for working the DX using Reduced bandwidth (RB-TV) modes.

Introduction

The aim of the Portsdown project is to enable an amateur radio 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.

New builders are recommended to build a Portsdown 4 which, when used with an Adalm Pluto, is integrated with the Langstone Microwave transceiver software enabling an advanced multimode narrowband and DATV transceiver covering 70Mhz to 6GHz for under £350. Full details on the Portsdown 4 are on this wiki page.

Outline specification

Outline specification of the Portsdown 4 system is as follows:

• Frequency coverage depends on the SDR used but covers 50, 71, 146 MHz, 437 MHz, 23cms, 13cms and 3.4GHz bands.

• MPEG-2 and MPEG-4 (H264) video encoding

• DVB-S, DVB-S2 and DVB-t transmission and reception

• DATV receiver capabilities using external MiniTiouner hardware

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

• Wide range of Symbol rates from 125 Ks to 4Ms* including Reduced Bandwidth (RB-TV) modes and “normal” DATV modes

• 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

System overview

At the heart of the Portsdown system 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 enables the system to be used as a standalone unit without further need to connect up keyboard and mouse. If the LCD is not available, the system can be controlled by using an external PC connected over a wired or wi-fi network (console mode).

The Portsdown 4 can also be controlled from a web browser (on a PC, tablet or smartphone); full details here: Portsdown 4 Web Control.

RF Generator and DATV Modulator

Depending on the version (see below) the output from the RPi is connected to one of the following units which modulates the RF carrier and produces the DVB-S or DVB-S2 DATV signal.

• BATC Filter Modulator board. DVB-S only. Portsdown 2020 only.
• DATV Express Board (no longer available). DVB-S only. Portsdown 2020 and Portsdown 4.
• LimeSDR (Mini or USB). DVB-S and DVB-S2. Portsdown 2020 and Portsdown 4.
• Adalm Pluto. DVB-S and DVB-S2. Portsdown 4 only.

Audio and video inputs

The Portsdown transmitter will take audio and video inputs from the RPi camera, an EasyCap composite video USB dongle, C920 webcam and a USB sound card / dongle - all these are readily available from ebay and Amazon. It will also accept an externally encoded Transport Stream from a PC or a LinkPi encoder.

Portsdown DATV receiver

On Portsdown 2020 and Portsdown 4, if you plug a MiniTiuoner or a PicoTuner into the RPi USB port and select "Rx" on the top level menu, you will have access to a fully functional DVB--S/S2 DATV receiver. If used with a Knucker tuner, DVB-T transmissions can also be received.

The received signal is displayed on the 7" touch screen. It is also available as a UDP output on the network enabling it to be viewed on a larger PC using VLC or a similar software.

For more details on DATV receptions see https://wiki.batc.org.uk/DVB-S/S2_Reception

Portsdown Test Equipment

The Portsdown 4 includes some very useful test equipment features including 6GHz RF signal generator, Noise figure meter, frequency sweeper and noise power meter.

See this wiki page Portsdown Test Equipment for more details.

Portsdown streamer to BATC.TV

The Portsdown can be used to stream to the BATC streamer - see https://wiki.batc.org.uk/Configuring_your_channel#Streaming_from_the_Portsdown

Meteor Viewer

The Portsdown build includes the capability to view 10 kHz of spectrum from an SDRPlay RSPdx. This capability is intended to be used to view the reflections of the GB3MBA beacon from meteors. Full details here: Portsdown MeteorView.

Further information

Portsdown Hardware

Full details of all the hardware required to build a Portsdown system is listed here Portsdown hardware

Technical Index

An index of technical reference pages for the Portsdown system can be found here Portsdown Technical Index.

HDMI Repeater TX Build Instructions

The Portsdown 4 can be used with an Elgato Camlink 4K HDMI capture dongle and a LimeSDR as the basis of an all-digital repeater transmitter (see CQ-TV 277). The software setup is described here Portsdown 4 HDMI Repeater TX Card Setup.

Portsdown Evolution

There are now 4 distinct Portsdown versions:

Portsdown 4

The latest version of the Portsdown is the Portsdown 4. This uses the Raspios Buster legacy operating system on a Raspberry Pi 4 with a 7 inch screen and a LimeSDR or ADALM Pluto. Unlike the previous version changes, it does not maintain hardware compatibility with the classic (filter-modulator) Portsdown.

The Portsdown 4 can transmit and receive DVB-S, DVB-S2 and DVB-T. The transmit capabity requires a LimeSDR or Pluto SDR and the receve capability requires a MiniTiouner (DVB-S/S2) or Knucker Tuner (DVB-T).

New builders are recommended to build a Portsdown 4 which, when used with a Adalm Pluto, is integrated with the Langstone Microwave transceiver software enabling an advanced multimode narrowband and DATV transceiver covering 70 MHz to 4 GHz for under £500.

The first release of the Portsdown 4 was in late July 2020. Constructors can build their own SD Cards using the install file on GitHub BATC Portsdown 4 GitHub Page. Pre-programmed SD Cards are also available from the BATC Shop.

New developments will be fielded in the Portsdown 4 software, and may not be back-ported to the Portsdown 2020.

Portsdown 2020 Buster

The Portsdown 2020 is Raspberry Pi 3 based running the Buster legacy operating system - Portsdown 2020. This software includes support for the LimeDVB firmware on the LimeSDR Mini and also supports the use of standard firmware on the LimeSDR USB and the LimeNET Micro.

The LongMynd receive capability has been improved with the addition of a player that will display some H265 signals. It will also control an external Jetson Nano with an HDMI capture device to allow the transmission of high definition H265 signals.

This version will continue to be actively supported, but most new developments will be reserved for the Portsdown 4.

Portsdown 2019 Stretch

This was the second version, using the Raspbian Stretch Operating System - Portsdown 2019. Support for the 7 inch touchscreen was added and some WebCams could also be used as a video source. Audio capability was added for H264 encoding, and early support was provided for the LimeSDR Mini.

Later versions also supported the LongMynd receive software enabling good DATV reception using a MiniTiouner.

Again, this version is no longer supported, although it will continue to work as built.

Portsdown 2018 Classic

The original version was launched in 2017 - Portsdown 2018. It was based on the Raspbian Jessie operating system running on a Raspberry Pi 3 with a 3.5 inch touchscreen. It used the BATC-supplied Filter-Modulator board and could take video from the Raspberry Pi Camera or the EasyCap. It would transmit DVB-S MPEG-2 with audio, or H264 without audio.

This version is no longer supported, although it will continue to work as built.