General > General Technical Chat
Squirrel Cage (Filament?) Lamps interfere with aircraft radio on approach!
Gyro:
I saw this story on the BBC news site yesterday but can't find it now...
Apparently commercial aircraft have been suffering radio blackouts in a localised area at 6000-10000ft on approach to Glasgow (UK) airport. Tracing the flight data back, they managed to track the blackouts back to a particular location and reported it to Ofcom for investigation.
Ofcom sent out their trackers, who finally narrowed the interference down to some unsuspecting homeowner who had bought a few 'squirrel cage' style LED filament bulbs from one of the usual culprits! Apparently the squirrel cage format formed an efficient enough antenna at the (I think) 118 and 122MHz commercial aircraft comms bands to pump out enough power a vertical pattern to block them out while the aircraft on approach were still at significant altitude. Presumably the noise source was something like broadband rectifier switching noise!
The potential implications for widespread broadcast interference from large numbers of these imported 'cheapies' are pretty horrible.
Here's the relevant Ofcom page... https://www.ofcom.org.uk/about-ofcom/latest/features-and-news/interference-issue
The BBC story made reference to a discovery, many years ago, of the same antenna effect with squirrel cage format incandescent filament lamps. Presumably radiating some external noise source, but I can't remember the details.
EDIT: From the photo on the Ofcom site, it's possible that they were actually incandescent filament ones - I don't know now!
Zero999:
The photograph in the article appears to be a standard incandescent lamp. I'm glad Ofcom are going after the sellers, rather than the home owner, who I hope managed to get a refund.
Gyro:
Yes, it seemed intuitive that they would be LED, given the EMC emissions of cheap lamps. I'm not sure how likely it would be for incandescent lamps to be that efficient an antenna for mains bourne interference. I'm pretty sure the BBC article said LED, they probably gathered more detail from Ofcom.
Either way, it looks like a pretty good antenna design!
EDIT: Hmm, the plot thickens...
https://www.emcrules.com/2017/04/can-incandescent-light-bulbs-cause.html
http://www.redca.eu/EUANB%20Documents/EUANB%20TGN%2035%20Guidance%20on%20the%20benign%20character%20of%20filament%20%20lamps%20May%202017.pdf
http://bulbcollector.com/forum/index.php?topic=1101.0
Thread title changed.
bd139:
That was a rather interesting rabbit hole. Thanks for posting.
Wonder if that explains the shitty 2m noise around here in evenings. Not that I have a radio around any more.
CJay:
Was discussed at some length on the RSGB tech or workshop mailing list I think, I wonder if the real problem was a crappy dimmer and the lamp was just an efficient radiator...
Navigation
[0] Message Index
[#] Next page
Go to full version