3 ms·

Well you are in the reactive near-field, so the antenna will de-tune, hence the power amplifier won't see it's ideal match, and not deliver as much power. All

Well you are in the reactive near-field, so the antenna will de-tune, hence the power amplifier won't see it's ideal match, and not deliver as much power. All depends on antenna design and orientation, assuming they don't use active impedance tuning. The base station also tells the phone to back-off. If the TX were running at full power, the battery will die quickly. Leave your phone in a metal, security cubby and your battery will die quickly; no power control and worse-case antenna loading. Also the highly asymmetric data usage these days. Very little energy on the uplink. FWIW I design antennas and amplifiers for a living. The only time I'd worry about RF exposure is to the cornea; that is a proven hazard. RF burns are a right of passage for PA designers, and are harmless as it's the outer skin layers.

johnr2 7y ago
> RF burns are a right of passage for PA designers, and are harmless as it's the outer skin layers. A literal example of skin effect?
- madengr 7y ago
  Yep. Put your finger on the corner of the output coupling cap on a 50 Watt S-band PA. It will turn your skin black from the charring, but doesn't penetrate into the live tissue. Just don't leave it on too long. Could probably gives non-permanent tattoos with this method.
sjwright 7y ago
> Leave your phone in a metal, security cubby and your battery will die quickly Which is the best selfish reason to remember to switch on flight mode on an aeroplane. (Also when you’re trekking in areas where you know cell coverage is nonexistent.)
labawi 7y ago
> If the TX were running at full power ... Leave your phone in a metal, security cubby and your battery will die quickly If the phone can't hear a network (not just faint signal like airplanes on certain heights), would it actually transmit? I think the battery drain would be from active RX searching for networks instead of sleeping. You get a similar though probably lower effect, when in roaming without setting a fixed network - an idle phone without crapware will burn way more energy.

johnr2 7y ago

> RF burns are a right of passage for PA designers, and are harmless as it's the outer skin layers. A literal example of skin effect?

madengr 7y ago
Yep. Put your finger on the corner of the output coupling cap on a 50 Watt S-band PA. It will turn your skin black from the charring, but doesn't penetrate into the live tissue. Just don't leave it on too long. Could probably gives non-permanent tattoos with this method.

sjwright 7y ago

> Leave your phone in a metal, security cubby and your battery will die quickly Which is the best selfish reason to remember to switch on flight mode on an aeroplane. (Also when you’re trekking in areas where you know cell coverage is nonexistent.)

labawi 7y ago

> If the TX were running at full power ... Leave your phone in a metal, security cubby and your battery will die quickly If the phone can't hear a network (not just faint signal like airplanes on certain heights), would it actually transmit? I think the battery drain would be from active RX searching for networks instead of sleeping. You get a similar though probably lower effect, when in roaming without setting a fixed network - an idle phone without crapware will burn way more energy.