Engineering FM – Part 5

A little break (strangely coincidentally, just as my penultimate term ended and my final year project got finished and handed in) later, and here we are again – another post in my series on engineering FM transmission at a community radio station.

This time I’m going to be talking about how to properly power a transmission system, and how best to deal with uninterruptable power supplies (UPSes) in terms of cabling, monitoring and long-term care. Continue reading Engineering FM – Part 5

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

Engineering FM – Part 1

This post is the first in a series of posts I’m going to do covering some of the engineering aspects of setting up a Community FM Radio station in the UK, and the lessons I and others learned while setting up the system.

First a bit of background. The station I helped set up, Insanity Radio, will be launching its FM transmissions in the coming weeks, and is a station run and operated entirely by students at Royal Holloway, University of London. The station started back in the 90s broadcasting on FM using a low-power rented transmitter, licensed under Restricted Service Licenses (RSLs) which only allowed for a week or two of broadcasting at a time. The station eventually moved to full-time AM operation, under a Low Power AM license. Back in 2006, a previous manager applied for a license for Community Radio, to permit FM broadcasting on a permanent basis, and in 2009 that license was awarded to Insanity by Ofcom, the UK’s radio regulatory body.

Our license was awarded for a 25 watt EIRP mast to be installed on campus. So in 2009/2010 we got the ball rolling with planning. Continue reading Engineering FM – Part 1