Radio-frequency spectrum usage in West Cambridge

Markus Kuhn – work in progress

This page aims to collect information about the use of the radio-frequency spectrum on the West Cambridge site of the University of Cambridge, specifically in or near the William Gates Building, 15 JJ Thomson Avenue, Cambridge CB3 0FD, 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 evolve into something 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 pre-emphasised audio also stereo-difference and RDS information.

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

Digital Audio Broadcast

There are four nominally 1.536 MHz wide DAB channels centred 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/DAB+ ensemble)

Digital radio in the United Kingdom

TV broadcast

TV broadcast in the UK (as of 2020) happens in the 470–694 MHz band (channels 21–48, was 21–69 before May 2020). Channel 38 is reserved for licenced wireless microphones, channel 70 contains 2 MHz of licence-free spectrum.

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

The nearest TV transmitter is Sandy Heath (24 km west-southwest, TL204494).

Since 17 June 2018:

Other TV transmitters include Sudbury (channels 29, 31, 37, 41, 44, 47) and Tacolneston (channels 39, 40, 42, 43, 45, 46).

Related links

• Ofcom Spectrum:
  • Spectrum information portal – Wireless Telegraphy Register (CSV)
  • Technical parameters for broadcast radio transmitters
  • Digital television transmitter details