My scenario is that at ground level I do not have phone signal.

At around 20m height I get quite a good phone sinal, including internet.

I would like to use an Android phone to use it for voice calls from my computer (perhaps via wifi/bluetooth) and have good signal antennas to catch as much signal as possible from the cell tower.

Also, I will use it as hotspot, hence the need for good wifi and bluetooth signal.

I have tried this with my iPhone, but unfortunatelly, I cannot have voice calls when the iPhone works as hotspot.

  • @K7AAY Yes, I am in Romania right now, but the question works for any country with similar problems. May 19, 2020 at 8:48
  • Frequencies used will differ, which is why I asked. frequencycheck.com/countries/romania suggests frequency bands used are 800MHz, 900MHz, 1800MHz, 2100MHz, and 2600MHz. Are you aware of any other frequencies used?
    – K7AAY
    May 19, 2020 at 17:47

1 Answer 1


Since very few cellphones nowadays have external antennas, and they are not Android but are 2G only, a cellular repeater or femtocell at 20m elevation is recommended.

Layout diagram active repeater from https://www.waveform.com/pages/cell-phone-repeaters

It must match the cellular voice and data frequency bands used by your provider, wherever you are, and may require regional regulatory approval. They will work, as adding another cellphone (Android or otherwise) may or may not work, especially since the sensitivity and rejection figures needed to determine if that second phone would work well are rarely published. A repeater also eliminates the need for another cellphone and another SIM card.

An active repeater adds signal gain, whereas a passive repeater doesn't. Therefore, an active repeater is preferred.

The following picture shows two antennas coupled together; if there's an active repeater between the antennas instead of just cable, that would be ideal and much more likely to work with no problems, rather than an unamplified passive approach.

If there is no femtocell or cellular repeater approved, let's talk about external antennas coupled through low-loss cable to form a passive repeater. passive repeater L50 ohm LMR400 cable would be my choice for cable; see https://info.wilsonpro.com/ty-installationguide/ and https://www.wilsonamplifiers.com/blog/understanding-coaxial-cables-the-complete-guide for more.

There are apps for your phone which can provide the location of the cell towers you connect to at that 20 meter height. A Yagi-Uda or other directional antenna can be pointed at that cell tower, and a cable dropped from that position to your cellphone. However, that depends on knowing what frequency bands your cellphone carrier uses, as directional antennas are very frequency-specific.

Both of those suggestions let you continue to use your existing iPhone, and its Bluetooth connectivity, without buying another SIM card and paying for another cellular device every month.


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