Following a number of visits over several weeks the repeater team have now found a workaround that prevents the trunking radio interference from taking over the system.
Maxwell has put a huge amount of effort into the problem over this time and he now has an excellent understanding of how the Philips PRF1520 operates. It should be said that this is a very complex radio as it can be used in many ways. There are dozens of configuration jumpers and they need to be just right for our particular usage.
The main change is to use the PRF1520’s internal CTCSS hardware at 91.5Hz.
In the past when VK5RPM was transmitting and mixing with two or three other transmitters the receiver would open and we would hear the interference. This was because the 91.5 decoder was inside the controller and audio (the nasties) were fed into the audio system even though the controller was not responding to the mute.
We have now activated the CTCSS detect in the PRF15 which means that if there is no 91.5 Hz tone, not only is the mute not activated, but the audio is also inhibited.
The repeater operation is now less susceptible to the interference. It will not show up at all if communication is coming via our links but if the incoming user’s signal on 146.3 is weak, you will hear white noise in the background or may even cause the weak signal to drop out.
This is not a cure for the interference, it just means we will not be bothered by it and we’ll have some peace!
The cause of the interference is still being investigated.