Passive signal redirection

CClaudio991 · May 16, 2021

Passive signal redirection

Hello specialists 🙂

I have my car in a large underground car park (3m underground with thick reinforced concrete) and absolutely no cell phone reception down there. So no LTE, 3G, Edge or anything else. No emergency call either.

Now I would like to ensure that my car has a mobile reception so that I can preheat it or charge/stop it using my mobile phone. This only works via the mobile network, not via WLAN (which wouldn’t be available either).

Just behind my parking space is a natural ventilation shaft with a metal grille covering it.

If I stand in the ventilation shaft and hold the phone up, I suddenly have mediocre LTE reception. (approx. 2 bars)

Basically I just want to redirect the weak signal so that the car (antenna is about 5m away) can receive it. It doesn’t have to be much.

I don’t want an active amplifier. On the one hand, this is probably forbidden anyway and on the other hand, it requires electricity. Since it is a large garage, you would have to get the consent of everyone involved, which would probably be hopeless.

That’s why I (as a layman!!!) imagined a passive signal redirection. Of course, this doesn’t make the signal stronger, but rather weaker. But since it is available in poor quality a few meters from the car, I would have hoped that it could work over a short distance.

Can anyone give me any advice or tips?

I was thinking of something like this: [710376 | Smarteq Wireless LTE multi-band antenna, Smartblade, black 698… 960 MHz/1710… 2690 MHz FME female | Distrelec Switzerland]. ? ext_cid=shgooaqchde-P-Shopping-Fallback&pi=30115274&gclid=CjwKCAjwhYOFBhBkEiwASF3KGbz3Gwpz_vGfianrb0sgpV-LvViJCi1fanii91mqUGM7h7uIxdGudBoCnLkQAvD_BwE)

But I would need a small antenna on both sides (glued to the air shaft) and an HF connecting cable in between.

Can that work? What would I bring to it?

Of course it won’t be a good reception. But I have hope that this might be enough.

Thank you!!

user109 · May 16, 2021

@Claudio991 see here: https://www.youtube.com/watch?v=U8f4DhE3Ka8

CClaudio991 · May 16, 2021

Thanks, I’ve already seen that too.

I would have preferred to buy something ready-made.

That doesn’t seem to have worked for some people either.

But thanks anyway.

Maybe other ideas will come.

user109 · May 16, 2021

@Claudio991 it always depends on what frequency band is nearby. The coax cable must not be too long because of the attenuation on the cable. It’s also in the comments, it’s not a cookbook solution.

There is no such thing as ready-made to buy, DIY.

Trying over studying.

A repeater is really expensive, costs a few thousand francs and must be registered and approved by Swisscom-Mobile.

Google this term “passive antenna amplifier LTE”, but it is the only legal solution, which is not available as a kit!!!

Due to individual location-related situations.

CClaudio991 · May 16, 2021

The cable (probably) wouldn’t have to be too long.

From the air shaft top to bottom so that the second antenna points out at the bottom.

Hopefully 2-3m should be enough.

Yes, then occasionally I go looking for all the components…

Thank you very much.

But further ideas are always welcome.

suisse · May 16, 2021

Why doesn’t this work via WiFi?

Modern vehicles have an app for this and it only runs via LTE?

I’m asking because you may have a socket on your PP and perhaps Powerline (with WLAN) could be a possible solution?

CClaudio991 · May 16, 2021

WiFi is not available.

If the car is asleep, it can only be woken up via the app via mobile communications. An SMS is sent internally and you can then communicate with the car via the app.

Therefore no WiFi.

The car deactivates WiFi as soon as it falls asleep.

There is a socket, but powerline doesn’t work because it’s a completely different phase than my apartment.

Electricity for electric cars comes directly from a separate transformer station

suisse · May 16, 2021

Too bad.

Just out of curiosity: what kind of vehicle is this?

CClaudio991 · May 16, 2021

There are several vehicles (not all mine, but also neighbors)

2x Tesla Model 3

1x VW ID.3

1x Audi eTron

3x Renault Zoe

But everyone has the same “problem”

suisse · May 16, 2021

Can’t you work together to find a solution?

CClaudio991 · May 16, 2021

There are about 83 more cars in the garage. All combustion engines and no one wants/needs mobile phone reception.

Since it’s a majority decision, we have a bad card…

suisse · May 16, 2021

Do you have individual power connections or charging management?

I’m no expert, but there is charging management that is managed via an LTE router.

You could take advantage of that. Of course, this requires the appropriate majority. Maybe bring this up in a meeting.

WalterB · May 16, 2021

@Claudio991

What does the property management think if you were to install WiFi in the underground car park and then use your cell phone with Wi-Fi calling?

But I’m not sure if your car’s mobile receiver can do that too?

CClaudio991 · May 16, 2021

We have charging management because this is mandatory if there is more than 1 charging station.

This is brought together via its own WLAN network. But we’re not allowed to access the Internet through that. We also need SMS access…

The administration doesn’t do anything if we don’t give them a joint mandate with a majority vote, since everything is owned and not rented.

suisse · May 16, 2021

I didn’t quite understand the SMS thing, it definitely doesn’t sound like a 2021 solution.

With Powerline (I know, problem with the phase, but Devolo Magic also partially runs on other phases) + Wifi Calling you get SMS.

(https://www.devolo.ch/support/faq#c34530)

Unfortunately I don’t have a suggestion for you.

But it’s nice that you use charging management.

Werner · May 16, 2021

@Claudio991

There is a great mobile reception in our underground car park with around 100 spaces.

The background is that the caretaker also has his workshop there and should always be reachable via mobile throughout the entire settlement…

Maybe you just had to convince the caretaker and the rest will take care of itself….-)-)

CClaudio991 · May 16, 2021

Convincing the caretaker is no use.

It is property and the majority decides about it.

Our layman’s knowledge is that cars wake up with a text message.

In any case, they automatically turn off the WiFi in the car when the car falls asleep. And it can only be woken up and controlled using an app via mobile communications.

Tested outside x times with WiFi hotspot and mobile phone reception.

So unfortunately we need mobile phone reception.

WiFi is also good for the cars - when they are awake. For everything else and updates…

Thanks anyway.

suisse · May 16, 2021

Ok 🙂

You don’t need SMS. WiFi is enough.

Have you even tried Powerline? If not, then try a Magic 2 device from Devolo.

Then you know whether it works or not.

CClaudio991 · May 16, 2021

I tried Powerline.

It does not work.

There is a separate transformer (150kV to 400V). Powerline no longer works.

WiFi does NOT work!!!

The car turns off its WiFi when it goes to sleep.

Only the LTE module remains active. There is nothing with WiFi at this point until it wakes up.

millernet · May 16, 2021

At Sunrise-UPC there would be a possible solution for 3G and 4G coverage indoors in the form of a femtocell: [https://www.sunrise.ch/de/business/produkte-und-loesungen/mobile/mobile-as-a-service/perfekter-mobilempfang-in-gebaeuden/business-indoor-box.html] (https://www.sunrise.ch/de/business/produkte-und-loesungen/mobile/mobile-as-a-service/perfekter-mobilempfang-in-gebaeuden/business-indoor-box.html)

However, this must be connected to the Internet with a network cable with a minimum bandwidth of 20/2 Mbit/s.

There are similar offers at Swisscom, but probably much more expensive and oversized for your use case: https://www.swisscom.ch/de/business/enterprise/angebot/enterprise-mobile/inhouse-mobile-services.html