Use a SDR (Software Defined Radio) to find out which frequency band your phone works on. This is actually really good fun and much easier than it sounds. The SDR costs about $24 and can be used with open source software such as GQRX with gives you a pretty amazing spectrum analyser. Check out this video which shows my own cell phone on band 20:

A good quality external antenna arrangement is absolutely essential and the best cable, fittings and antenna should be selected.

This part is much easier - it's just a panel antenna and it can be mounted on a wall in a convenient location.

The kit comes with a few 'easy to solder' components, so solder them on, being careful to get the voltage regulator the right way round. The flat part of the regulator faces away from the board.

The cables in the kit have female SMA type connections, so make sure that the antenna cables themselves terminate in male SMA with appropriate adapters if required. The kit comes as in the photo above, left, so there are no antenna or heavy cables or adapters supplied.

Make sure there is appropriate strain relief to prevent the heavy cables floating around and destroying the signal booster.

Before attaching the Uno to the booster PCB, upload the code. Code for the Arduino is 'Work in Progress', but this simple code will control the booster via the two push buttons. The code could easily be adapted to use the slider instead:

#include "SPI.h"
const int slaveSelectPin = 7; // LE for the VGA.
const int QPL9065VPD = 3;
const int QPL9065VBYP = 4;
const int leftButtonPin = A2;
const int rightButtonPin = A3;
int leftButtonPinValue = 0;
int rightButtonPinValue = 0;
int leftButtonStatus = 1;
int rightButtonStatus = 1;
int sensorPin = A5;    // select the input pin for the potentiometer
float sensorValue = 1.00;
int rabbits;
void setup() 
{
  Serial.begin(9600);
  Serial.println("Test Begin!");
  
  // set the slaveSelectPin as an output:
  pinMode(slaveSelectPin, OUTPUT);
  pinMode(QPL9065VPD, OUTPUT);
  pinMode(QPL9065VBYP, OUTPUT);
  
// Set QPL9065VPD and QPL9065VBYP both to LOW to enable them both and disable bypass.
//  digitalWrite(QPL9065VPD, LOW);
//  digitalWrite(QPL9065VBYP, LOW);
  
// Set QPL9065VPD to HIGH and QPL9065VBYP to LOW to disable them both and disable bypass.
  digitalWrite(QPL9065VPD, LOW);
  digitalWrite(QPL9065VBYP, HIGH);
  
}
void loop(void) 
{ 
  readPushbuttons();
 
   //sensorValue = analogRead(sensorPin);
   //sensorValue = 0;
   delay(1000);
   //writePotToVGA();
}
void readPushbuttons()
{
// For low power press left hand button.
// For high power press right hand button.
// For off press both buttons together.
   leftButtonPinValue = analogRead(leftButtonPin);
   rightButtonPinValue = analogRead(rightButtonPin);
   if(leftButtonPinValue==0)
     {
     leftButtonStatus = 0;rightButtonStatus = 1;
     }
   if(rightButtonPinValue==0)
     {
     rightButtonStatus = 0;leftButtonStatus = 1;
     }
   if((leftButtonPinValue==0)&&(rightButtonPinValue==0))
     {
     rightButtonStatus = 1;leftButtonStatus = 1;
     }
   if(leftButtonStatus == 0)
     {
     digitalWrite(QPL9065VPD, LOW);
     digitalWrite(QPL9065VBYP, HIGH);
     Serial.println("LOW,HIGH ...... Low power");
     }
   if(rightButtonStatus == 0)
     {
     digitalWrite(QPL9065VPD, LOW);
     digitalWrite(QPL9065VBYP, LOW);
     Serial.println("LOW,LOW ...... High power");
     }
   if((rightButtonStatus == 1)&&(leftButtonStatus == 1))
     {
     digitalWrite(QPL9065VPD, HIGH);
     digitalWrite(QPL9065VBYP, HIGH);
     Serial.println("HIGH,HIGH ....... Everything is OFF");
     }
}
void writePotToVGA()
{
  sensorValue = analogRead(sensorPin);
  sensorValue = sensorValue*63/1023;
  rabbits = sensorValue;
  Serial.println(sensorValue);
  Serial.println(rabbits);
  SPI.begin();
  digitalWrite(slaveSelectPin, LOW);
  SPI.transfer(rabbits);
  digitalWrite(slaveSelectPin, HIGH);
  SPI.end();
}  

Disconnect the usb programming cable and attach the Uno to the PCB. Connect a suitable power supply cable of delivering at least 2 amps at either 9v or 12v. 9v is preferable.

Turn on the power supply and reconnect the usb cable if you want to monitor the device through the serial port.

By default, the device is in 'standby' mode with no transmission. Press and hold the left hand button and monitor the response on a cell phone and/or the SDR. Wait a few minutes and if the response is negligible, press and hold the right hand button.

To put the device back into standby, press and hold both the buttons. Simple !