Radio-frequency spectrum usage in West Cambridge

Markus Kuhn

This page aims to collect information about the use of the radio-frequency spectrum in or near the William Gates Building on the West Cambridge site of the University of Cambridge, in Cambridge, England (52° 12′ 39.33″ N, 0° 5′ 31.28″ E; 52.210925° N, 0.092022° E; TL4292059074, openstreetmap).

The original purpose of this list is to be a planning resource for compromising-emanations experiments in the Security Group at the Computer Laboratory. As such it has a particular initial focus on continuously active broadcast transmitters in the VHF and UHF bands (30 MHz to 3 GHz) that show up as a clear peak on a spectrum analyzer.

However, it is hoped that the list may be of wider interest to anyone near Cambridge trying to understand the source of RF interference, wondering where all the peaks on a spectrum analyzer come from, looking for a sample signal of a given format, or performing other RF experiments. Contributions of information regarding other RF signals specific to the Cambridge region are also most welcome.

FM radio broadcast

The 88–108 MHz band is reserved for FM broadcasting stations, which typically occupy a bandwidth of around 150 kHz and include in addition to 50 µs preemphasised audio also stereo-difference and RDS information.

BBC Radio 1-4 transmitters: Madingley (TL392594, 260W, mixed polarization), BBC Radio Cambridgeshire: Madingley (TL392594, 1 kW, mixed polarization)

Digital Audio Broadcast

There are four nominally 1.536 MHz wide DAB channels centered at

• Block 11A = 216.928 MHz (Sound Digital ensemble)
• Block 11C = 220.352 MHz (local ensemble)
• Block 11D = 222.064 MHz (Digital One ensemble)
• Block 12B = 225.648 MHz (BBC National DAB ensemble)

Digital radio in the United Kingdom

document

TV broadcast

The nearest TV transmitter is Sandy Heath (24 km west, TL204494, 1000 kW, horizontal polarization), which will switch off its last analog PAL channels on 13 Apr 2011.

UK UHF Channels are nominally 8 MHz wide. If n is the channel number then

• n × 8 MHz + 302 MHz is the lower band limit
• n × 8 MHz + 310 MHz is the upper band limit
• n × 8 MHz + 303.25 MHz is the I/PAL video carrier
• n × 8 MHz + 306 MHz is the centre frequency
• A + or − following the channel number indicates that the center frequency is offset by +0.167 MHz or -0.167 MHz (for DVB-T).

Before 13 April 2011, we had also analog transmissions:

• Ofcom digital switchover transmitter details – Anglia Region

Related links

• Ofcom Spectrum Information