Portsdown 2019

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Revision as of 08:14, 5 February 2019 by G8GTZ (talk | contribs) (Portsdown 2018)
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The Portsdown 2019 DATV system has been designed to provide an easy way to “get on air” with Digital ATV at a relatively low cost covering all of the commonly used modes, so enabling it to be used on ATV repeaters but also for RB-TV DX working.

The 2019 Portsdown is significantly different to previous versions in that the system no longer uses the custom built Filter Modulator card which has been replaced with an off-the-shelf LimeSDR Mini.

The LimeSDR Mini plugs in to the Raspberry Pi USB port, preferably via a powered USB hub and produces an RF output from ~ 30MHz to 3.5GHz.

This guide is in a number of sections which cover detailed descriptions for hardware and software, how to build and configure the system, some advanced features and an FAQ.

Portsdown 2018

Portsdown 2018 has been superseded by Portsdown 2019 but there is NO intention to discontinue support of the 2018 model. If you would still like an F-M board, we suggest you post on the wanted section of the forum - https://forum.batc.org.uk/viewforum.php?f=14 - or blank PCBs for home construction are available here - BATC shop item 10.

All the wiki information on previous versions of Portsdown is still available here.


The Portsdown 2019 will accept video input from a composite video source, the Pi camera, some WebCams or integrated stored test cards. It will then encode these as MPEG-2 or H264 with stereo audio.

Using a LimeSDR Mini it will transmit DATV on frequencies between 30 MHz and 3.5 GHz. Typical power output varies with frequency and is plotted here: LimeSDR_Mini_Output_Power_Levels.

DVB-S and DVB-S2 modes are available from the LimeSDR Mini, with QPSK, 8PSK, 16APSK and 32APSK. Symbol rates are generally limited to 1000KS and below (down to 66 KS), but some H264 modes will work at 2MS.

Hardware System Diagram

Here is the latest system diagram. Note that only one of the displays is required; either the 3.5 inch or 7 inch; the digital variable attenuator is only required if you want fine (<3 dB steps) control over your PA drive levels. The Lime Gain control on the Portsdown can be used to set the coarse output level.

20190120 Portsdown 2019 Block.jpg

Building the system

The Portsdown 2019 uses the majority of the 2018 Portsdown hardware.

Portsdown 2019 Software

The Portsdown 2019 uses the same software as later versions of the Portsdown 2018 system which is known as Portsdown 2018/2019 and is based on the Raspberry Pi's Raspbian Stretch operating system.

Initially configuring the system

Waveshare 3.5 inch screen

To get started, once you have an SD card with the Portsdown 2019 software loaded, simply put the card in the SD slot on the RPi.

If you have a Waveshare touch screen the Portsdown 2019 software is pre-configured ready to use and no initial configuration is required. Connect the Waveshare 3.5 inch touchscreen (being careful to align the pins correctly) and apply power to the RPi and the user interface should appear.

Element 14 7 inch screen

A new or upgraded SD Card (version 201902070 or later) will also work out of the box with the 7 inch screen. It will start up and reboot to load the correct drivers the first time you use it, but after that will boot directly to Menu 1.

No Touchscreen or Advanced Options

If you do not have a Waveshare 3.5 inch screen or the Element 14 7 inch screen, or you wish to enter the system advanced set-up pages you will need to do an initial setup - see this guide for more details: Initial setup 2019

Controlling the Portsdown 2019 system

Once the system is configured, you can control the Portsdown transmitter in one of 2 modes: by the use of the touchscreen or through the console using a second computer.

  • Touchscreen mode How to use your Portsdown transmitter using the Touchscreen LCD only
  • Console mode Use this mode to configure advanced settings such as WiFi or non-standard screens.
  • Changing system setup How to change Portsdown transmitter settings when in Touchscreen mode
  • QPSKRF or Ugly mode Notes on this special test mode and the limitations when using it
  • Setting up the WiFi How to set up the WiFi on the RPi3 Portsdown Transmitter

Advanced features

Portsdown 2019 is not just a DATV transmitter but has several advanced features which are or may be available in the future:

On line support / social media

There is a Portsdown area on the BATC forum where the BATC core team and wider ATV community will answer your questions and posting results of the latest builds and on air tests. https://forum.batc.org.uk/viewforum.php?f=103

Note that the BATC core team do not regularly visit Facebook pages - time is just too short to monitor everything and it's not easy to follow threads on Facebook. If you need a question answered please post on the BATC forums first.

Additional information

Filters and driver amplifiers are not part of the Portsdown project but VERY important

The Portsdown user's community including a map showing where user locations