Years ago I used to know the frequency¹ for the downlink of Capital Radio in London's 'Flying Eye', the aircraft used to scout about for travel blackspots. It was a useful frequency to have as there was no better place to get the latest travel news. I also remembered that there was an uplink from the studio on around 455 MHz too.

One quiet afternoon I thought I'd have a tune around to see whether or not the old up and downlink frequencies were still active. Listening around 467 MHz, there seemed to be no sign of the downlink (though being around 25 miles outside of central London and with a downlink power of less than a Watt, this wasn't perhaps, that surprising). The uplink, however, is still active on 455.075 MHz.

What was rather odd, however, was to hear dozens of Imam's calling their congregation to prayer on frequencies just below this at around 454.5 MHz. Was this some freak long-distance propagation carrying signals from arabic speaking countries in North Africa or the Middle East? Was it a freak spurious response on my receiver, allowing reception of, perhaps, satellite radio? Were these the link frequencies to the numerous 'Radio Ramadan' stations that appear on the FM band during the festival?

No. It was none of these. Instead it seems that there is a radio service, established in around 2000, called 'On-Site Religious Observation' or OSRO. This a a licensed radio service which allows any religious body to use the old Wide Area Paging (WAP) channels to deliver voice communications to pagers. What a good use for these otherwise quiet channels: to allow Muslim's their right to hear the Imam's call without the need to build noisy minarets, just build unsightly radio towers instead!

A bit more digging revealed that there are all sorts of interesting frequencies in the range 454 to 458 MHz as listed below:

454.0125 to 454.8375 MHz OSRO/WAP
454.84375 to 454.98125 MHz Cab Secure Radio (CSR)²
454.9875 to 455.475 MHz Programme Making and Special Events (PMSE)³
455.475 to 455.850 MHz Airport Security and Operations (455.5125, 455.5375, 455.5875, 455.625, 455.6625, 455.675 and 455.6875 MHz also used for CSR)
455.850 to 456.000 MHz Fire Service
456.000 to 456.9875 MHz Private Mobile Radio (PMR) Simplex and Duplex use
457.000 to 457.250 MHz Fire Service
457.250 to 457.475 MHz PMSE
457.475 to 457.500 MHz Fire Service
457.500 to 458.500 MHz Scanning Telemetry (457.525, 455.5375, 457.550, 455.5625 and 457.575 MHz also used for On-Board Ship Communications)

With Ofcom considering reconsidering its previously aborted plans to re-align the band it will be interesting to see where these services end up. And in the meantime if anyone has the frequency used for the Flying Eye's downlink, do share it with us!

¹467.6625 MHz if I remember correctly.
²Radio system used by Network Rail in areas where rail services have no conductor and thus the driver can not leave the cab to commnunicate with the signaller.
³Links and talkback for radio stations, TV studios, film sets, theatres and so on. Could be used by production team at a Kylie Minogue concert for example...

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