I want to improve the LTE signal that I receive indoor where I work and after some researching I'm thinking about a passive LTE repeater (Outdoor Antenna <--> Cable <--> Indoor Antenna).
However; I am not sure which LTE antennas to buy.

The LTE bands that I want to repeat are mainly:

  • B20 ( 800 MHz)
  • B8 ( 900 MHz)
  • B3 (1800 MHz)
  • B1 (2100 MHz)
  • B7 (2600 MHz)

with my mobile operators in Italy being:

  1. Vodafone
  2. Iliad
  3. Wind-Tre

The nearest LTE BTS to which my phone connects are:

  1. 4G+ 4CA (B7 B1 B3 B20) [2 km away]
  2. 4G+ 4CA (B7 B1 B3 B20) [8.5 km away]

This is a NetMonster screenshot from indoor room R1 ground floor. enter image description here

and this from outdoor point A

enter image description here

My Speed Tests from room R1 are:

While from the outside at pint A, the results are much better.

The building is as follows, divided in two floors (3M + 3M high) and I want to improve the LTE signal in the room R1 (groud and first floor) by installing a passive LTE repeater with two antennas in points A and B connected via a coaxial cable (in red).
The LTE BTS are located on the left of point A.

enter image description here

Which are the best LTE antennas and coaxial cable to use in this case? For the outdoor antenna I think it is betteter an omnidirectional MIMO considering that there are two near BTSs and the outdoor signal is good enough. Regarding the indoor antenna I don't known what to use. Is a generic MIMO good enough? Do they have a specific name?

Will the indoor antenna installed at point B be able to improve the signal also for rooms R0, R2, R4 ?

Are the NETGEAR 6000451 omnidirectional https://amzn.eu/d/aHk3mko and the KASER K5GPB14V3 180° directonal https://amzn.eu/d/8qF74CU ok for my case?

Update 1

The outdoor antenna is installed at 6 meters from the ground, while the indoor antenna is at 2.5 meters from the ground.

I first bought the KASER K5GPB14V3 180° and the NETGEAR 6000451, connected them using the pair of 10 meters coax cables, and I was able to get around 5 times the speed (both download and upload) I had without them, but only if I literally placed my phone on top of the NETGEAR indoor antenna.

I thought it was the fault of the indoor antenna, so I replaced it with a Kaser OmniDirectional https://www.kaserstore.com/collections/mondo-4g-5g-lte/products/kaser-antenna-5g-4g-lte-esterno-mimo-omnidirezionale-698-2700-3300-3800-mhz-guadagno-fino-12-dbi-cavi-da-10m

The two antennas are now connected using the 20 meters pair of cables, however I can not notice any improvement even with the smartphone placed on top of the indoor antenna. Is it due to the length of the cambles? I may connect them using just the 10 meters cables by using another pair of connectors, but I fear it will not have enough power to cover at least room R1.

Which amplifiers should I buy if this is the case? Do I need a Bi-Directional Amplifier (BDA)? Can I replace a BDA with two amplifiers (one to amplify the oudoor antenna and the other to amplify the indoor antenna)? E.g. HTOOL HT004 100K-6GHz https://it.aliexpress.com/item/1005005950859267.html Notice that each antenna is MIMO and has two cables.

Update 2

Now the setup of the antennas is as follows:

The red line connecting the antennas are two cables of total length 20 meters. I would like the antenna B to serve at least both the ground and the first floor of room R1 and the top half of room R0 at ground floor. enter image description here

1 Answer 1


Direct Answer:

Use a directional antenna outside: The Kaser Pannel you referenced or these Log Periodic and Panel alternatives.

Use an omnidirectional antenna inside: well tuned indoor antennas or less conspicuous covered antennas.

The cables included with these antennas already cover the distance you need. However, they are both male SMA, so you will need this adapter to connect between them.

Possible Improvements:

If you are putting the antenna on the side of your building, but at the same height as your indoor portion, (as in your picture): you will want something directional to reduce feedback from indoors and to add gain between you and the BTS. If more stations are added, so they are in opposite directions, you may want to switch to putting an omnidirectional antenna on top of the building. Gaining that extra height can be a big improvement in signal strength.

Play around with the placement of your indoor antennas, you can benefit from spatially separating them so that you can take better advantage of MIMO. You will notice in the Log Periodic antenna above, the two are turned 90deg from each other. This creates separation in polarity and matches what the BTS does.

Once you have all your antennas in place, you can add a repeater inline if you find that your signal strength has not increased enough. In this case, you will not need to change the antennas you already have.


Take your outdoor antenna and wire it into a 4G modem. This will prevent interference, as the 4G signal outside is on a different frequency from the WiFi inside. It will also let you take advantage of the 4G signal in a wired network if needed.

(Question Update) I want to stress that this is your best option. A 4G modem could make use of the MIMO and the antennas you have already purchased. I have had good performance out of this netgear, but if you can afford it, the new version upgrades from 4G to 5G and has the wireless router built in.

Cables and Connectors:

All of the antenna and repeaters use a 50 Ohm impedance, so as long as you use a 50 Ohm cable, you will be ok. (75 Ohm is used in television.) N-type and SMA are the most common connector types and it is very easy to find adapters between the two, or cables that go from one to the other, like the ones that come with the Kaiser antenna.

It's worth noting that some consumer gear is actually RP-SMA which reverses which connector has the center pin, so if you go buying extension cables, make sure you don't accidentally buy the wrong one. (Note the adapter included with the Bingfu antenna.)

Active Repeater: (Question Update)

Using a simple amplifier will not work well as any communication needs signal in both directions. If you put two amplifiers in opposite directions, they will create a feedback loop and you will have worse signal that you would without it. You will instead want to use a repeater which has filters to only amplify uplink signals in one direction and down link signals in the other. Unfortunately, cellular repeaters are not MIMO and you do not have low enough signal levels to benefit from a repeater. (If you had your inside levels outside and almost nothing inside, I would recommend a repeater.)

Indoor Antenna: (Question Update)

The Kaser Omni is a high gain antenna meaning it will have great signal in one direction at the expense of signal in other directions. This works well for the top of building where you want signal from the cell towers far away, but not from the sky or ground. Think of it as a disk perpendicular to the antenna. But indoors, you want signal right below the antenna. More like a dome. If you find that you have good signal 2m away from the omni antenna but at the same height, then switching to a low gain ceiling antenna will help. Whether you use the "indoor antennas" link or the "ceiling antenna" link, you will want to put them on opposite ends of R1, or even have one in R2 and one in R4.

  • Hi, can you check the update in my question? Can you suggest which amplifiers to install?
    – 1Z10
    Commented Apr 4 at 14:03
  • Thanks for the additional details. I updated the question with the current setup picture. I tought the KASER OMNI 360° at point B would have worked well both for coverage due to the omnidirectional signal and for supporting both 4G and 5G in future. So, there is no way to use these two Kaser antennas? Even by installing the amplifiers at point A and poit B at an appropriate distance?
    – 1Z10
    Commented Apr 4 at 18:38
  • 1
    For a passive repeater: I would just place both of the antennas you purchased outside (in different locations) and run them to cheap indoor, low gain antennas. That would give you 4 different indoor antennas. Space them out as much as possible: Top floor R0; Top floor R3; Bottom floor R2; Bottom floor R4. (Either outdoor antenna will work great with a cellular modem.)
    – Alphy13
    Commented Apr 4 at 18:46
  • If holding your phone at the same height of the indoor antenna works, you could try keeping it but lowering it to 1m off the floor. It would be better to use one of the low gain antennas I referenced above, but try lowering your indoor antenna first.
    – Alphy13
    Commented Apr 4 at 18:56
  • 1
    If you use amplifiers, you need filters. They are not available commercially, besides in cellular repeaters (which have them built in). Without filtering, the signal from the output line will go back in the input line and amplify over and over like holding a microphone close to a speaker.
    – Alphy13
    Commented Apr 4 at 18:59

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