Hello LF,
There's an MF broadcaster in the Faroe Islands, Utvarp Foroya, on
531kHz, which is a good daytime signal up here in Shetland.
Their MF transmitter finally broke down, beyond economic repair in May
and they were QRT, seemingly forever, but in early August, around the
7th I believe, they re-appeared on the band, and I was initially
pleased to hear them - it's always useful to have a strong signal close
to our own allocation for off-air measurements, antenna comparisons etc.
However around that time I noticed my grabber screen was being wiped
out by what looked like wideband noise. I initially thought "summer
thunderstorms" and ignored it, but it persists, day and night.
Recently I actually listened to the RX audio and found it to be
noise-like but varying, in time to the modulation of Utvarp Foroya. They
are radiating noise 30kHz or more away from their carrier frequency!
Listening on an SSB/CW receiver I can hear modulation artifacts down to
485kHz.
I've brought it up with RSGB Intruder Watch, who've been in touch with
OFCOM at Baldock. Unfortunately they can't here the wide signal, down
there in the south of the UK.
Contacts in GI and EI can certainly here the wide modulation, and
raised noise floor though.
I am currently making some measurements with a spectrum analyzer and it
makes interesting viewing.
The signal is at least 30kHz wide, slowly rolling down to the noise
floor of the analyzer (-115dBm in a 300Hz resolution bandwidth).
Looking at 693kHz (BBC) and 630kHz (a Norwegian service) shows them
to have very sharp bandwidth limiting +/- 5kHz, as you'd expect.
The Faroes signal seems to roll on forever....
I wonder if anyone else can detect this spreading modulation.
If you look at my online grabber at
http://www.gm4slv.org.uk/grabber2.htm
you'll see a raised noise level, but occasional periods of
inky blackness, with the normal very low background noise level I enjoy
here, when the programme material is silent.
I'll scan the print outs of the spectrum plots and pop them on the web
tomorrow, and send some copies to OFCOM.
The worry isn't so much that they're spreading over our allocation
(annoying though that is) it's that they are very noticable, in these
northern waters, on the 518kHz NAVTEX frequency.
Regards,
John GM4SLV
Clousta
Shetland
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