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vfrmedia Alex@rtnVFRmedia Suffolk UK @social.tchncs.de

Old roaming Tom Cat (zwerfkater) but still young at heart. Toots EN, (NL,FR,DE). #DevOpa - interested more in retro tech / culture / aesthetics than new stuff. Also transport and public infrastructure in general (with a UK/European focus)

Welcome to the secret goose shed!

Avatar is a tabby point Siamese cat - header picture is a Stentor FM radio transmitter designed in the Netherlands; popular with small pirate radio broadcasters in late 1980s

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Comments 15
Yes, the blue rectangle at 0:30 is an arduino uno
  • @yogurtwrong I'm impressed they don't have problems with it glitching out, especially with the electromechanical part of the lightshow close by which appears to be switching 230V mains directly on those open metal contacts!

  • I wrote an open letter to artists and other creatives who are thinking about giving the fediverse a chance:
  • @[email protected] I see far more diverse art on here compared to any other social network I have ever used (which tend to use the algorithms to pigeonhole you into what they think your tastes are and how they relate to whatever categories advertisers want)

  • Expensive school uniforms don't make kids better at maths, so why are schools so focused on them?
  • @thepixelfox @Zagorath @pineapplelover @dgriffith @ajsadauskas

    a few years back I started a discussion about which countries had uniforms (its not universial, and tends to be the UK and Commonwealth mostly); and a parent from USA said their school has an approved dress/colour code but not full branded uniform which is a lot better as it doesn't tie parents to getting their clothes from a handful of places

  • Is “harvesting” small amounts of electricity a fools errand?
  • @rarely the claims of "poor reception" caused by "large scale" nearfield power harvesting are from Communications Ministry officers from some decades ago (I mistakenly referred to modern Ofcom rather than the British Post Office which investigated these things until the 1980s), it is possible they just wanted to discourage this practice for the safety of those involved whilst not also opening a can of worms about human exposure to RF (it was Cold War era and much info was classified)

  • Is “harvesting” small amounts of electricity a fools errand?
  • @rarely Temporarily lighting small lamps from nearfield RF with a TX power of some kW is definitely possible, a family friend who was the engineer at Radio Caroline in the 1960s did it on board the ship as a demonstration to visitors; but didn't use any antenna nor leave the lamps around to light up the deck (it would have created hassle with unwanted stray RF, and there was plenty about already!). Its not common these days as TX sites are designed to keep people out of the nearfield for safety.

  • Is “harvesting” small amounts of electricity a fools errand?
  • @rarely the historical reports of issues I've read about are from mid-late 20th century in areas near high power LF/MF stations that would be in the nearfield - from the Wiki article

    > absorption of radiation in the near field by adjacent conducting objects detectably affects the loading on the signal generator (the transmitter).

    so it would be noticeable, and viewed as an undesirable thing. Harvesting (small) amounts of power in the far field would not cause issues.

  • Is “harvesting” small amounts of electricity a fools errand?
  • @rarely this is why things behave differently when very close to the TX (how close will of course depend on the TX power and frequency/wavelength)

    https://en.wikipedia.org/wiki/Near_and_far_field

  • Is “harvesting” small amounts of electricity a fools errand?
  • @rarely if you are /that/ close to the antenna an extra tower, or any large amount of metal making the station more directional will definitely be unwanted, both by tradio station engineers and the Communications Ministry (licenses often require a particular directional pattern). But this is more an issue with LF and MF where waves are larger. At UHF/SHF frequencies for wifi harvesting could work but at present the component count required makes it less viable than other power sources.

  • Is “harvesting” small amounts of electricity a fools errand?
  • @rarely if the link below federates correctly, here is a receiver that uses just the power of the signal, but from a 4kW transmitter 32km away there are only a few tens of milivolts, enough to be amplified by the line in of a desktop PC to listen to the audio but certainly not enough to light any lamps (even an LED). Maybe I could light an LED from our wifi signal close to the access point, but I don't have any RF detector diodes to hand that work at 2,4 GHz

    https://social.tchncs.de/@vfrmedia/110873682071137732

  • Is “harvesting” small amounts of electricity a fools errand?
  • @rarely a radio receiver uses *much* less of the power than lighting up the fluorescent tubes would (it wasn't just one lamp) and this incident happened close enough to the TX that it could upset the SWR of the transmitter output stages - if it /was/ possible to do this without creating problems elsewhere then every tall transmission tower would use the RF to power their aircraft warning lamps rather than a separate power supply...

  • Is “harvesting” small amounts of electricity a fools errand?
  • @drdabbles @rarely

    A few years back some farmer living in Droitwich, England (where the Radio 4 longwave transmitter is situated) lit his barn by connecting an antenna to fluorescent light tubes.

    It worked, but also created a "not-spot" in the radio reception which the BBC really didn't like (its part of critical national infrastructure!) - officers from Ofcom turned up at his door, made him take the lot down and ordered him to use more "normal" power sources..

  • Cornershop - Brimful Of Asha, Norman Cook Mix (1998)
  • @perishthethought @Aesecakes

    its about a British South Asian binge listening to Bollywood soundtracks sung by Asha Bhosle..

    https://en.wikipedia.org/wiki/Asha_Bhosle

  • Welcome to Lemmy, hosted at tchncs.de
  • @milan @[email protected]

    I get a message when I try to log in "De registratie is in afwachting van goedkeuring." (registration is waiting for approval - for some reason everything Lemmy related comes up in Dutch on my browser and has done for some years 😁 )

  • Welcome to Lemmy, hosted at tchncs.de
  • @[email protected] @milan

    I just tried to register, but I got a message that flashed up to the screen about email settings (and disappeared before I can read it) and some circle in a box is spinning at the bottom..