Radio Caroline 648 kHz
Wireless Waffle previously sang the praises of the boat trips to visit the Ross Revenge, the home of former radio pirate, Radio Caroline. We also noted that they had been awarded a licence to operate a 1 kiloWatt transmitter on 648 kHz in the Suffolk and north Essex area.Well, it seems the engineering bods on the east coast have managed to get it together, and recently test transmissions on 648 kHz were spotted by a number of listeners, such as a DXer in Humberside who posted the video below on YouTube.
Though you may not be able to interpret the waterfall display shown on the video, what you see is the Radio Caroline signal in the middle. The two bright lines either side represent radio stations on the adjacent frequencies (639 and 657 kHz respectively). Normally, for AM broadcasting, each station would be allowed to occupy half of the bandwidth between its assigned frequency and the adjacent channels, meaining that it would extend +/- 4.5 kHz either side of its centre frequency. It is this limitation they gives medium and long wave broadcasting their characteristic 'muddy' sound, as the limitation in spectrum also restricts the amount of audio bandwidth that can be transmitted.
It's therefore notable that the Radio Caroline transmission on 648 kHz extends far closer to the adjacent frequencies than 4.5 kHz. It appears closer to +/- 6.5 kHz wide (or maybe even more). This would allow the station to transmit a wider audio bandwidth and thus sound a little 'brighter' on-air. Such derogations from the norm are not unusual as the medium wave band has become emptier, as there is more space for stations to spread out and sound better.
As an example, the three audio clips below have been filtered with different bandwidths. Just click on the relevant button to hear the difference (note that this doesn't work in all browsers.
| Audio Bandwidth | Play |
|---|---|
| 15 kHz, stereo (FM Stereo) |  |
| 6.5 kHz, mono (extended bandwidth AM) | |
| 4.5 kHz, mono (standard bandwidth AM) | |
Given that of the neighbouring frequencies, the nearest stations on 639 kHz are in the Czech Republic and Spain (previously crowned the queen of medium-wave broadcasting) and on 657 kHz in Spain (again) and North Wales, it seems unlikely that the additional bandwidth being used by Radio Caroline will give any problems and we are sure that listeners will enjoy the cleaner, brighter sound that they will have on-air.Mike
Tuesday 19 December, 2017, 16:10
Whatever happened to AM stereo ? It was a thing in the US and Australia in the late 1980's/early 1990's. The UK radio authority in the early 1990's announced they were doing some tests of the Motorola C-QUAM system but none of the ILR stations adopted it for a permanent service.Friday 22 May, 2020, 12:58
Radio Caroline have been running their 648 kHz service for a little over a year now. Their audio still sounds like it's coming through a sock, so their audio bandwidth is very severely limited.
In the daytime, the signal strength is tolerable over much of East Anglia, but between dusk and dawn, they're just completely wasting electricity. They are totally flattened by co-channel European stations. It's almost impossible to hear their puny kilowatt even within a couple of miles of their site after dark.
Their programming leaves a lot to be desired - the current crop of presenters aren't much good.
The halcyon days of the mid-70s and early 80s are long gone. They're just living on their (rather tainted) reputation. Their time has long passed - it's sad, but they're just a poor quality community AM station now.
They have the chance to do something really good, but are just peopled with "Davy Doubledecks" types who say little more that "that was.... this is....". They've missed their chance!
Friday 22 May, 2020, 12:59
Radio Caroline have been running their 648 kHz service for a little over a year now. Their audio still sounds like it's coming through a sock, so their audio bandwidth is very severely limited.In the daytime, the signal strength is tolerable over much of East Anglia, but between dusk and dawn, they're just completely wasting electricity. They are totally flattened by co-channel European stations. It's almost impossible to hear their puny kilowatt even within a couple of miles of their site after dark.
Their programming leaves a lot to be desired - the current crop of presenters aren't much good.
The halcyon days of the mid-70s and early 80s are long gone. They're just living on their (rather tainted) reputation. Their time has long passed - it's sad, but they're just a poor quality community AM station now.
They have the chance to do something really good, but are just peopled with "Davy Doubledecks" types who say little more that "that was.... this is....". They've missed their chance!
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