Transmitting ATV pictures
Overview
The basic components of an ATV transmitter system are: a camera or camcorder, a suitable ATV transmitter, and a high-gain antenna — typically a Yagi — with horizontal polarisation used on all frequencies in the Melbourne area.
Cameras
Just about any camera that produces video your transmitter will accept will work as your video source. If you don't have a camera, the video out of a computer or recording device can be used. The most common is the camcorder variety. Older cameras work well and can be picked up at places like Cash Converters for next to nothing. The audio out of the camera microphone is fine, but most stations use external microphones.
Frequency selection
There are 2 video inputs to the VK3RTV ATV repeater: 1245 MHz and 1253 MHz, both are DVB-S, DVB-S2, or DVB-T inputs. See the VK3RTV frequency plan for full details.
From most areas of Melbourne, stations are having great success getting full-quieting digital signals into the repeater with modest Yagis (1–2 m boom) or small gridpac dishes, good low-loss feed lines, and 1–10 W of power.
Transmitters
Transmitters for sending a signal to VK3RTV can be DVB-S, DVB-S2, or DVB-T. Options include:
- The Adalm Pluto with ATV firmware (available via the Equipment & Software page), fed via OBS or VMIX running on a computer — currently the easiest approach.
- BATC Portsdown — a DVB transmitter built from a Raspberry Pi and an Adalm Pluto or Lime SDR. See the BATC website for details.
- HIDES HV-320E DVB-T transmitter.
- SR Systems transmitters (no longer in production, but occasionally found second-hand).
All currently available transmitters will require an amplifier (and possibly a preamp) to achieve an acceptable output level. For ideas on transmitters, kits, or parts see ATV equipment sources.
Antennas
On 23cm, 1–10 W of power and an antenna of 10 dB gain or more is generally sufficient from most areas of Melbourne with line of sight to Mount View. The antenna should be horizontally polarised and fed with low-loss coax such as Times Microwave LMR400 or similar.
Loop Yagis and gridpac dishes are the most commonly used antennas for VK3RTV. Loop Yagis are normally home-made but can also be purchased. A spreadsheet for calculating loop Yagi dimensions can be found on the Equipment and Software page. Gridpac dishes for 23cm can be purchased from various sources including Chinese internet vendors.