4 ms·

From messing about with MR scanners: An MR Faraday cage attenuates the RF signal about 100db (according to the engineer who built it). Phones work as long as t

From messing about with MR scanners: An MR Faraday cage attenuates the RF signal about 100db (according to the engineer who built it). Phones work as long as the door is open 1mm or so. Blue tooth works through the cage just fine. Wifi doesn't work very well anywhere near the cage. MR scanners get nice pictures with the scan door open, but the if the scanner next door has its door open (so 2x scanners running with door open), images are wrecked. Also, the coastguard sends you grumpy letters if you leave the door open and scan (at 3T).

accoil 1y ago
Why does the coastguard get involved?
- lostlogin 1y ago
  I think that 3T scanners are effectively transmitting on one of their frequencies in my region. We image hydrogen which has a precessional frequency of 42*3MHz at 3T (though most ‘3T’ MR scanners seem to be more like 2.8-2.9T). So they must use something at around that frequency. All I know for sure is that we got asked to stop blasting that RF out. Sometimes it is convenient to open the scan door while imaging.
  - genewitch 1y ago
    126-128MHz if i am reading what you said correctly is aviation (aircraft use 108-136MHz, AM) - but i am unsure of what that notation means and the AI explanation made my eyes glaze. I'm unsure why the FCC wouldn't be the ones to complain; but i've never managed to annoy a government with my radio-work yet, so i am not sure who calls who to send someone to knock on the door. either way https://www.ntia.gov/sites/default/files/publications/january_2016_spectrum_wall_chart_0.pdf https://www.ntia.gov/sites/default/files/publications/januar... also i only glanced the the US band plans, if this setup isn't in the US, then you'd have to find the relevant band plan for your area (although the US band plan for HF will be fairly accurate, HF is hemispherical on a bad day and global on a good day)
    - lostlogin 1y ago
      > I'm unsure why the FCC wouldn't be the ones to complain Are you mentioned - US only. I’m in New Zealand.
      - genewitch 1y ago
        https://www.rsm.govt.nz/assets/Uploads/documents/radio-spectrum-usage-chart-march-24.pdf https://www.rsm.govt.nz/assets/Uploads/documents/radio-spect... as far as why the coast guard, that's a dive too deep for me today. Interesting story, though, on your part!

accoil 1y ago

Why does the coastguard get involved?

lostlogin 1y ago
I think that 3T scanners are effectively transmitting on one of their frequencies in my region. We image hydrogen which has a precessional frequency of 42*3MHz at 3T (though most ‘3T’ MR scanners seem to be more like 2.8-2.9T). So they must use something at around that frequency. All I know for sure is that we got asked to stop blasting that RF out. Sometimes it is convenient to open the scan door while imaging.
- genewitch 1y ago
  126-128MHz if i am reading what you said correctly is aviation (aircraft use 108-136MHz, AM) - but i am unsure of what that notation means and the AI explanation made my eyes glaze. I'm unsure why the FCC wouldn't be the ones to complain; but i've never managed to annoy a government with my radio-work yet, so i am not sure who calls who to send someone to knock on the door. either way https://www.ntia.gov/sites/default/files/publications/january_2016_spectrum_wall_chart_0.pdf https://www.ntia.gov/sites/default/files/publications/januar... also i only glanced the the US band plans, if this setup isn't in the US, then you'd have to find the relevant band plan for your area (although the US band plan for HF will be fairly accurate, HF is hemispherical on a bad day and global on a good day)
  - lostlogin 1y ago
    > I'm unsure why the FCC wouldn't be the ones to complain Are you mentioned - US only. I’m in New Zealand.
    - genewitch 1y ago
      https://www.rsm.govt.nz/assets/Uploads/documents/radio-spectrum-usage-chart-march-24.pdf https://www.rsm.govt.nz/assets/Uploads/documents/radio-spect... as far as why the coast guard, that's a dive too deep for me today. Interesting story, though, on your part!