Testing the Product

A project log for Cell Phone 4G LTE Repeater / Booster / Femtocell

An outside pole mounted aerial picks up 4G signals which are then filtered, amplified and re-transmitted through a second inside aerial.

capt-flatus-oflahertyCapt. Flatus O'Flaherty ☠ 07/22/2017 at 16:570 Comments

After assembling the new 4 layer PCB with my manual pick and place machine I soldered on all the larger parts by hand and plugged it in ....... No response! Ah well, I thought the odds of it working were about 75% so it was no great surprise :( But since it works at relatively low voltage, it's always worth touching some of the connections with a finger as this is a really quick way of either totally destroying the components or galvanising them into action. I am one of the fortunate creatures on this planet who are blessed with electric fingers !

Anyway, the 'Electric Finger' test worked and suddenly the device started working ! It seems I had left out an important power connection to the VGA, which was fixed by soldering on an extra wire.

The other useful thing that I did was to upgrade the outside antenna and cable:

This antenna was installed about 20' up in the air, with the pointy end directed towards my local 4G base station, which is about 8 miles away. The cable is very 'high performance', with 3dB loss over 15 metres and the antenna itself has a gain of about 6dB so that's a net gain of 3dB.

During testing, the VGA was behaving a bit strangely, so I used one of the 'intersection' antenna sockets to effectively avoid using it, and to my surprise, the 2 stage LNA chip provided plenty of power on it's own when receiving the signal from the base station. Note that I am making no attempt to transmit to the base station at this time as it's not needed where I live - my phone's transmit capability is fine on it's own. Transmitting to the base station has to be done very carefully as getting it wrong can cause very serious problems, so I'm going to attempt this much later in the project.

The test showed a 15dBm increase in signal strength with just the first stage of the LNA in operation and a massive 40dBm with both stages working, which gave a useful range of about 10m inside a building. It was very useful to be able to control the device like this as quite often, for convenience, the phone is positioned quite close to the inside antenna and in this case just using the primary stage of the LNA was highly beneficial.

The video below shows the device being controlled with 2 push button switches via an Arduino Uno: