Stations all around Australia have been reporting interference from signals far far away over the past 24 hours (see our previous report).
It’s not aliens… it’s Sporadic E, an atmospheric effect that can happen at this time of year.
It causes signals in the 30-300MHz range to reflect off the E layer of the Earth’s atmosphere, around a hundred kilometers above Earth’s surface, instead of flying through into space.
radioinfo has consulted a number of technical experts about this today, with many surprised at the strength of the signal noticed by Rod Bryce, given that it was strong enough to carry the RDS data into his car dashboard as well as audio.
Radio people from all over Australia also reported experiencing the phenomenon after we wrote about it this morning.
Reminds me when I got 91.9 Sea FM Sunshine Coast in Canberra.
I had New Zealand romping in here at Coffs Harbour this morning.
Yeah I got Bendigo crystal clear. Smooth melbourne 91.5 was coming in patches too but not as clear.
And HiT107, Freah & MIX102.3 in Toowoomba – Still on now!
Fraser Coast clear as… in the Adelaide Hills
Sent star fm in tassie, which i picked up in warwick qld, an email but they didn’t believe me. All quiet now.
The worst on air sound goes to 101.3 Mixx FM Horsham, it was the best I have heard temp inversion for awhile, Adelaide and Adelaide Foot Hills were amazing signal, a few 2m contacts were made to VK3. The band was full. All River listeners in Brisbane hope you enjoyed Triple J regional Vic for your listening enjoyment.
100.3 hot fm makay i heard interfering with Nova fm in melbourne today
SCA’s National Radio Engineering Manager Steve Adler says some of his stations experienced Sporadic E today.
“We experienced Victorian and South Australian FM stations being heard in Queensland. Brisbane stations being heard in Tasmania and the RIVER 104.9 in Albury being head in Auckland! There was a fleeting glimpse of a New Caledonian FM station being heard in Queensland too.”
Adler says: “Sporadic E activity peaks predictably in the summertime in both hemispheres. Activity usually begins in mid-December in the southern hemisphere, with the days immediately after Christmas being the most active period.”
The last word on it comes from the technical team at the ACMA, who told us:
“Sporadic E propagation is the reflection of radio signals from ionised patches in the E layer of the ionosphere. This type of propagation was more common when channels 0, 1 and 2 were in use for analog TV, however, it also can affect FM radio signals.
“Signals from transmitters in the range 800 to 2600 kilometres may be received at levels several orders of magnitude greater than those which would normally be expected.
“Although sporadic E propagation is seasonal, propagation conditions may be such that when it does occur, high unwanted signal levels can be maintained for several hours.”
More information is available on various online sources including Wikipedia.
Thanks to Steve Adler of SCA, John Maizels of Technorama and ACMA Technical Department for the research on this report.