In the early hours of Wednesday 23rd October the BBC ran their yearly of their ReBroadcast Standby system on their FM radio network for 2024.

The line feed to all of the FM network transmitters except Wrotham was cut at times between 0130 & 0500 and test signals and tones were played instead, followed by normal station output. These tones travelled from transmitter to transmitter across the country, with each main transmitter picking up a signal from a nearby neighbour and rebroadcasting it outward for other main transmitters (including their onward relays) to hear.

On this page we'll feature some audio clips of these tests from various locations across the country courtesy of OARC members, as well as tracking the quality of the received signal as it moved up through the chain.

Here's what to expect:

SDR++ (lightweight, open source): https://www.sdrpp.org/

SDR Console (has more features, including scheduled recording mode): https://www.sdr-radio.com/console

Obviously this info was given pre-event, but we'll leave it here in case it's useful.

Easy mode: pick a single frequency, listen in WFM mode, record audio between 01:30 and 03:15, or leave it going all night and check it in the morning.

If you want to get a bit more technical and monitor more frequencies you'll want to record a baseband of a section of the FM Broadcast band. Remember, if you're planning to record a full chunk of baseband do remember that an FM signal is 200 kHz wide, so it will extend 100kHz past the dial frequency in each direction.

• I (hello, 2M0IIG here) am planning to record 10 MHz of spectrum (because I have a HackRF) between 89.8 and 99.6 MHz. This will encompass BBC Radio 1-4 in my location.
• R2 is on 89.9 MHz, so I am starting the recording at 89.8 MHz. You may want to run it a little beyond that even as sometimes signals at the edges of an SDR's “view” can be a little lower in signal strength.
• R1 is on 99.5 MHz, and 89.9 + 10 MHz = 99.9 MHz, so R1 is included in this.
• The centre frequency to set in SDR++ therefore is 89.8 MHz + 5 MHz = 94.8 MHz
• The day after I will playback this recording and individually “tune in” to stations that I see on the waterfall in WFM mode.
• At this point I will switch the recording configuration to record audio rather than baseband and record sections of what each station is playing

Here is a view of this setup in SDR++, with me tuned into my SDR live and listening to 94.3 MHz. You can see 94.8 MHz as the centre frequency. There are also a few nasty images and spikes, but this is to be expected with SDRs.

Map of receiver locations (and maybe TX locations) here.

• Mark 2M0IIG - IO85Gw (Black Hill Transmitter)
• Dan G5DSG -
• Tom M0LTE -

• Recording of tones broadcast via RBS
• Recording of any speech/music content broadcast via RBS
• Analysis of these recordings, referring to things like whether it was in stereo, whether there was any hiss, if the signal level dropped from the baseline, what the overall audio quality was, and so on.