Engineering FM – Part 4

Time for the exciting fourth instalment of my ongoing series on engineering at a small community radio station launching an FM service for the first time. In this post I’m going to be looking (somewhat briefly) at processing.

There’s been a place for processors ever since radio has existed, to make sure that audio input to a modulator doesn’t exceed the modulator’s input limits without making the audio itself sound bad. This typically involved an automatic gain control circuit, or AGC. As time went by, these evolved into multiband AGCs, processing in typically four chunks for LF, LMF, HMF, and HF audio segments. Clippers and limiters were also used to protect equipment but as stations aimed for a competitive edge processors became used to make stations sound louder and punchier by maximising the amount of modulation used at any time. Continue reading Engineering FM – Part 4

Introducing OpenOB

The next post will be part 3 of my Engineering FM series but it’s time for a quick diversion to introduce a tool I ended up producing, initially as a contingency plan, but later as a serious project, for implementing outside broadcast audio links and studio-transmitter links using the Real Time Protocol.

That tool is called OpenOB. The main resource for finding out more is the GitHub page hosting it. But I figured it deserved a proper introduction as I’ve had quite a few people asking after it via a post on the Rivendell mailing list. Continue reading Introducing OpenOB