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 polarization being used on all frequencies in the Melbourne area.

Cameras

Just about any camera that produces composite video will work as your video source. If you don't have a camera then the video out of a VCR can be used. ( just make sure the content is suitable ). The most common video camera is of the camcorder variety as a majority of people have one of these already. There are older more bulky cameras that can be acquired very cheaply but they need more light and are usually much larger ( but if cost is a factor then they work well ). The audio out of the camera microphone is fine for the audio to your transmitter but most stations are using external mic's.

Frequency Selection

At present, there are 4 video inputs to the VK3RTV ATV repeater: 1250MHz, and 10410MHz which are FM inputs and there is also a 1250MHz DVB-S input all with antenna's pointing west of Mt Dandenong, 1283MHz is a DVB-S input with antenna's pointing east towards the Yarra valley. See the frequency plan for more specifics.

From most areas of Melbourne, stations are having great success getting full quieting (P5) video into the 1250 MHz (FMTV) input with modest yagi's ( 3 - 6 foot boom ) and 1 to 10W of power. A P5 picture is obtainable on 10410MHz with clear line of sight to the repeater with a 30cm dish and 50mW or better.

Transmitters and Antennas

On 1250MHz, all that seems to be needed from most areas of Melbourne with line of site to Mt Dandenong is 1 - 10 Watts of power and an antenna of 10dB gain or more. The antenna should be horizontally polarized and should be mounted such that it has as line of site view of VK3RTV on Mt Dandenong. It should be fed with low loss coax such as Times Microwave LMR400 or similar.

Transmitters are normally constructed at home rather than ready made. There are 2 different varieties of which there are either home grown or kit form. See ATV equipment sources for ideas on where to get transmitters, kits or parts.