- Solutionselected by SamuelD
A car is a Faraday cage. Talking on the phone in the vehicle is the worst possible place for cell phones!
https://de.wikipedia.org/wiki/Faradayscher_K%C3%A4fig
Measuring cell phone reception with a network monitor:
[/t5/Mobile/Natel-Empfang-bricht-%C3%BCber-die-Staffelegg-immer-ab/td-p/525279](https://community.swisscom.ch/t5/Mobile/Natel-Empfang- breaks-%C3%BCber-die-Steffelleg-always-off/td-p/525279)
Everything else is reading coffee grounds.
If you want or need to make regular calls in your car, you should buy (or lease) a vehicle:
a) which has mobile phone-permeable car windows:
[/t5/Mobile/Natel-Empfang-bricht-%C3%BCber-die-Staffelegg-immer-ab/m-p/572974#M5863](https://community.swisscom.ch/t5/Mobile/Natel-Empfang- breaks-%C3%BCover-the-relay-leg-always-off/m-p/572974#M5863)
b) or improve cell phone reception with the help of an external antenna and a vehicle’s own cell phone module (=> rSAP/SAP).
https://de.wikipedia.org/wiki/SIM-Access-Profile
c) or using a device consisting of an indoor and outdoor antenna, similar to an InTrain repeater, to improve mobile phone reception inside the vehicle. For example: Skoda “Phonebox”:
[https://www.skoda-storyboard.com/de/press releases-archive/wireless-charging-for-the-smartphone-the-phonebox-from-skoda/](https://www.skoda-storyboard.com /en/press releases-archive/wireless-charging-for-the-smartphone-the-phonebox-from-skoda/)
https://de.wikipedia.org/wiki/Intrain-Repeater
The “Skoda Phonebox” acts as a passive mobile radio repeater. When using an active mobile radio repeater, for example an intra-repeater, the mobile phone signal to be sent via the indoor or outdoor antenna is amplified by a signal amplifier. When using a passive cell phone repeater, the cell phone signal to be sent via the indoor or outdoor antenna is not amplified by a signal amplifier.
Active mobile phone repeaters may only be used in Switzerland with the appropriate permission from the Swiss mobile phone provider (Swisscom, Salt, Sunrise). The use of active cell phone repeaters without the appropriate permission from the cell phone provider is illegal!
[https://www.bakom.admin.ch/bakom/de/home/geraete-anlagen/besondere-geraete/mobilfunk-verstaerker.html](https://www.bakom.admin.ch/bakom/de/ home/devices-systems/special-devices/mobile-radio-amplifiers.html)
Swisscom does not offer private customers an active mobile phone repeater.
Passive cellular repeaters have the disadvantage of limited range. The cell phone must be very close to the indoor antenna for sufficient cell phone reception. The maximum permissible distance between the indoor antenna and the mobile phone is usually 10 cm to 100 cm. The range of a passive mobile radio repeater is massively limited by the free space attenuation.
https://de.wikipedia.org/wiki/Freiraumd%C3%A4mpfung
If you want to implement a passive mobile phone repeater in the underground car park, you should first provide the information below:
https://community.swisscom.ch/t5/Mobile/Passive-Signalumlenkung/m-p/668182#M9180
observe!