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Calling for help beyond mobile coverage: PLB, satellite messenger, marine VHF and smartphone

Which distress device suits trips without mobile coverage?

Personal locator beacon (PLB), satellite messenger, marine VHF radio and the smartphone compared – for planning trips to remote areas or onto the water. Ranges, alert times and accuracies are deliberately not given. Registration, licensing and approval rules differ from country to country – check local rules.

Starting situation
Legend
Select methods to compare side by sideMethodRaises the alarm without mobile networkTwo-way communicationWithout subscription or licenceIntended for use on landBuilt for emergencies
Personal locator beacon (PLB): how it works, registration, activationYesNoPartlyYesYes
Satellite messengers and satellite SOS on phonesYesYesNoYesPartly
Marine VHF radio: MAYDAY distress call – basicsYesYesNoNoPartly
The phone as a signalling device: light, screen, sound, emergency functionDependsDependsYesYesNo

Legend:● Yes◐ Partly◇ Depends○ No* = note available

Personal locator beacon (PLB): how it works, registration, activation

Effort:
Low; register it
Needs:
Registered PLB, clear view of the sky
  • Raises the alarm without mobile networkYes

    Via an international satellite system for search and rescue.

  • Two-way communicationNo

    Alert only, no feedback.

  • Without subscription or licencePartly

    Usually no running costs, but registration requirements depending on the country.

  • Intended for use on landYes
  • Built for emergenciesYes

    Battery limited and usually not user-replaceable.

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Satellite messengers and satellite SOS on phones

Effort:
Low to moderate
Needs:
Device with an active subscription, charged battery, clear view of the sky
  • Raises the alarm without mobile networkYes

    Via commercial satellite networks; messages can take minutes.

  • Two-way communicationYes

    The response centre can ask questions.

  • Without subscription or licenceNo

    Without an active subscription SOS may not work – check before every trip.

  • Intended for use on landYes
  • Built for emergenciesPartly

    The battery must be charged.

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Marine VHF radio: MAYDAY distress call – basics

Effort:
Moderate; training
Needs:
Marine VHF radio, ideally with DSC; in many countries an operator certificate and licence
  • Raises the alarm without mobile networkYes

    Range limited by line of sight.

  • Two-way communicationYes

    Reaches rescue services and nearby vessels at once.

  • Without subscription or licenceNo

    Certificate and licence in many countries; in a genuine emergency anyone may generally send a distress call.

  • Intended for use on landNo

    Intended for maritime use – check local rules.

  • Built for emergenciesPartly

    Handhelds have limited power and battery.

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The phone as a signalling device: light, screen, sound, emergency function

Effort:
Low
Needs:
Charged smartphone, power bank
  • Raises the alarm without mobile networkDepends

    Without network, light, screen and sound remain; some devices offer satellite SOS in certain countries.

  • Two-way communicationDepends

    Only with network or a satellite function.

  • Without subscription or licenceYes
  • Intended for use on landYes
  • Built for emergenciesNo

    Sensitive to cold and wet; the battery is needed for many things.

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