VK3RTV
DIGITAL ATV

REPEATER STATUS : Fully operational DIGITAL TV Output

Transmitting ATV Pictures

Overview

Cameras

Frequency Selection

Transmitters and Antennas


 

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 computer or VCR / DVD player 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 usually need more light and are physically larger than the modern equivalent. If cost is a factor then the 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 for the audio to your transmitter but most stations are using external microphone'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 1255MHz DVB-S input all with antenna's pointing west of Mt Dandenong, 1276MHz is a DVB-S input with antenna's pointing east towards the Yarra valley. See the VK3RTV & Melbourne ATV 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. If you are transmitting a digital signal then there is not as much leeway for the weak signal. Everyone who is currently getting a good picture into the repeater with an analogue signal is getting perfect signal with a digital signal.

 


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.

A DVB-S digital transmitter for the digital input to the repeater can be bought from SR Systems in Germany as assembled boards that have to be wired together and placed in a suitable box. SR Systems also sell a completely assembled DVB transmitter as pictured above.

An analogue transmitter can be either home grown or kit form.

For ideas on where to get transmitters, kits or parts see ATV equipment sources.