ARDUINO RF power & SWR meter

This sketch will readout RF power and SWR from any SWR bridge (for example 'monimatch' type). As this 'monimatch' type of bridge is frequency dependant, the meter must be calibrated for every band. Because my primary interest was for VHF/UHF/SHF,  I have foreseen positions for 6m, 4m, 2m, 70 cm, 23cm and 13cm bands - but you can use the ARDUINO readout on HF as well. If you intend to build a HF or VHF bridge yourself, there are several designs available on the web : I recommend to take a look at the information herehere , here and there !

The meter will operate in 3 modes:

When the band is selected/changed, the display indicated the 'full scale' of power readout. With my type of bridge (some breakout part of mobile radio base station I presume, but working well till 2.4 GHz - I purchased it on a local flea market...) the power ranges from 1kw (6m band) to 400mW  (on 13cm).   Other possibility is  to build a directional coupler, many designs can be found on the net.  With my coupler, in the PEP power measurement mode, it is for example perfectly possible to measure the output of a WiFi access points ... Power range could be increased by adding some resistive voltage dividing network, as the maximum input on ARDUINO is +5v.  But is is essential that same power gives same voltage, both in 'forward' as 'reflected' mode (when the coupler is turned around).

The meter is indented to be battery powered, therefore there is a circuit to control the LCD backlight (drawing a lot of current) and monitor the battery voltage.

Front panel of PWR & SWR meter. Left = power switch, middle = mode select push-button, right = band change push-button

Forward power is 23.3 W  corresponding to +43.6 dBm

Below is the sketch  or download it here .   It was compiled with version 0022. Download the connection diagram (as pdf) here.  

See the meter in action on YouTube  http://www.youtube.com  

How to calibrate the power indication ?

Using a directional coupler which is not frequency compensated, the forward voltage (indicating the power) will be frequency dependant.  For a 'monimatch' type, the voltage will increase with frequency - or - otherwise said, the meter will become more sensitive at higher frequency (off course, as long as it is operated within  it's design frequency range).  The maximum voltage which can be measured by Arduino is +5v , this is limiting the range upwards - if necessary, a voltage divider must be foreseen (same on REFL side off course!) - according to your frequency, power & coupler.

To calibrate the sketch, follow the simple procedure below :

//CALIBRATION ROUTINE FORWARD VOLTAGE  ////////////////////
 
 // This routine prints on LCD the FWD voltage measured.
 // When no power applied, the FWD voltage displayed will be the diode voltage in mV
 // To calculate the calibration factor, take the reading (including diode voltage)
 // Uncomment this routine to enter calibration mode
 
 lcd.setCursor(0, 0);
 lcd.print("VoltFWD= "); 
 lcd.print(VoltFWD, DEC);   
 delay(500);                
 
 //   /////////////////////////////////////////////////////

PowCal=(VoltFWD²/Power) / 1000  (where power is expressed in Watt)

In our case : PowCal = 2500 x 2500 / 10 / 1000 = 625

#define PowCal2m     (625)    // 2m band

/*CALIBRATION ROUTINE FORWARD VOLTAGE  ////////////////////
 
 // This routine prints on LCD the FWD voltage measured.
 // When no power applied, the FWD voltage displayed will be the diode voltage in mV
 // To calculate the calibration factor, take the reading (including diode voltage)
 // Uncomment this routine to enter calibration mode
 
 lcd.setCursor(0, 0);
 lcd.print("VoltFWD= "); 
 lcd.print(VoltFWD, DEC);   
 delay(500);                
 
 */   /////////////////////////////////////////////////////

Remarks : 

(see my other ARDUINO stuff under 'PROJECTS' page)


/*
    ************************************************************** 
    *        POWER & SWR meter on 2x16 char LCD display          *
    *                  By ON7EQ  Aug 2011                        *
    ************************************************************** 

  The circuit:
  
 * LCD RS pin to digital pin 7
 * LCD Enable pin to digital pin 8
 * LCD D4 pin to digital pin 9
 * LCD D5 pin to digital pin 10
 * LCD D6 pin to digital pin 11
 * LCD D7 pin to digital pin 12
 * LCD R/W pin to ground
 * GND to LCD VO pin (pin 3) (contrast)
 
 * pin 13 = LCD backlight control (1= backlight ON). Use an emittor follower (like BC639) to control LCD backlight (this draws about 120mA) 


 * pin 4 = connect a piezo buzzer (other end to ground) 


 * pin A0 : SWR probe FWD  voltage input (SWR bridge type 'MONIMATCH')
 * pin A1 : SWR probe REFL voltage input   

    ! Set the diode forward voltage in variable 'Diode'.  For 1SS99 or other Schottky diodes, it is around 130mV @ 0,1mA


 * pin A5 : Power Supply Voltage input  


MODE SELECT : there are 2 possibilities to select mode :
--------------------------------------------------------

1° with 3 position toggle switch:

* pin Digital 2 : 'bip' Sound Switch : when grounded -> SWR 'bip' tone mode
* pin Digital 3 : PEP mode Switch : when grounded -> PEP mode

  When switch in center position : normal power/swr mode, instant power & dBm readout
  When using a center toggle switch, Pin 5 must be connected to +5v 
  If a 3-way toggle switch is present, it will be automatically detected and the variable 'PushButton' set accordingly.

  
2° with push button for cycling modes:

* pin Digital 5 : Mode push button : when grounded (pulse), next mode is selected
 ! the mode is stored in EEPROM & memorized for next boot


BAND SELECT : 
-------------
It can be necessary to apply different parameters / calibration factors per band.

* pin Digital 6 : BAND push button : when grounded (pulse), next band is selected
 ! the band is stored in EEPROM & memorized for next boot

 */

// include the LCD library code:
#include <LiquidCrystal.h>

// include math functions
#include "math.h" 

// include EEPROM write
#include <EEPROM.h>

// variables

#define TonePin      (4)    // Pin for beeper
#define ToneSwitch   (2)    // one end of 3 way toggle switch
#define PEPswitch    (3)    // the other end of 3 way toggle switch
#define ModeSwitch   (5)    // push button switch (no 3 way toggle switch)
#define BANDSwitch   (6)    // push button switch band change
#define LCDbacklight (13)   // output to power the LCD backlight


#define VoltSupplyMini (66) // minimum battery voltage expressed in 100mV (if lower, alarm is generated)
//                          // for µ7805, minimum 7v required



// voltage divider at A5  - select proper values so that voltage never exceeds 5v on A5 !
// With R1 = 1k2 and R2 = 4k7, max input voltage = 25v

#define R1           (12)   // from GND to A5, express in 100R  (12 = 1200 Ohm)
#define R2           (47)   // from + power supply to A5, express in 100R  (47 = 4700 Ohm)


// calibration variables for forward power : 
//     PowCal=(VoltFWD²/Power) / 1000  (where Power = Power over 50 Ohm in Watt)
// Carry out calibration with sufficient power !

#define PowCalHF     (100)    // HF band
#define PowCal6m     (21)     // 6m band
#define PowCal4m     (30)     // 4m band --> pmax @ 5000mV = 833 W (as example)
#define PowCal2m     (117)    // 2m band
#define PowCal70     (57)     // 70cm band
#define PowCal23     (3165)   // 23cm band
#define PowCal13     (64800)  // 13cm band

char* myStrings[]={"  HF ", "  6m ", "  4m ","  2m ", " 70cm"," 23cm"," 13cm"};


/////////////////////// 3 way-mode switch or pushbutton ? ///////////////////////////////////

int PushButton = (1);           // 1 = Pushbutton  /  0 = toggle switch
                                // there is an automatic detection in the display subroutine 

////////////////////////////////////////////////////////////////////////////////////////////

// modes
byte PEP = (1);                   // 0 if PEP measured
byte Tone = (1);                  // 0 if tone SWR tune (bip)

byte MODE = (0);                  // Mode 0 = instant power / Mode 1 = PEP / Mode 2 = Bip
byte BAND =(0);                   // BAND 0 = HF / 1 = 6m  / 2 = 4m / 3 = 2m  / 4 = 70cm  / 5 = 23cm  / 6 = 13cm

unsigned long DisplayTime = 0;    // timer display refresh
unsigned long PeakTime = 0;       // timer peak (PEP) detect
unsigned long BacklightTime = 0;  // backlight LCD hold time
unsigned long BandTime = 0;       // band display hold time

float VoltFWD = 0;
float VoltFWDmax = 0;
float VoltPEP = 0;
float VoltREF = 0;

unsigned int Diode = 130;         // diode forward voltage, expressed in mV

unsigned int PowCal = 103 ;       // calibration factor for power: PowCal=(VoltFWD²/Power)*1000
unsigned long PWR = 0;            // power (expressed in 100 mW)
unsigned int PowDis = 0;          // power for display
float SWR = 0;                    // SWR 
float Vratio = 0;                 // Voltage ratio VoltREF/VoltFWD

int SWRDis = 0;                  // power calculation for showing in display

int VoltFWDmini = 0;

unsigned long PWRmax = 0;         // the maximum power range, band dependant

int beeponce = (0);              // emit only 1 beep for modechange
int beepband = (0);              // emit only 1 beep for bandchange

int SWRtonePitch = (800);        // low lone = low SWR
int SWRtoneLenght = (100);       // long tone = low SWR

int debugled = (0);              // LED at pin13 = debug
int decay = (0);                 // PEP decay rate

unsigned int SupplyVoltage = (0); // Power supply voltage

byte RunOnce =(1);                // detect wether in SETUP or LOOP mode
byte DisplayCycle = (0);          // counts the cycles in display mode (for low volt alert)

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(7, 8, 9, 10, 11, 12);

// *************************************************************   
// ********************  S  E  T  U  P  ************************
// *************************************************************   

void setup() {

  //setup pins
  pinMode(LCDbacklight, OUTPUT);  //Backlight LCD display
  pinMode(PEPswitch, INPUT);      // if grounded --> 'PEP' mode
  pinMode(ToneSwitch, INPUT);     // if grounded  --> 'Bip' mode
  pinMode(ModeSwitch, INPUT);     // if grounded  --> cycle through modes
  pinMode(BANDSwitch, INPUT);     // if grounded  --> cycle through bands
  
  
  // set up the LCD's number of columns and rows: 
  lcd.begin(16, 2);
  
  
 // READ mode from EEPROM & set parameters
 MODE = EEPROM.read(1);
       if (MODE == 0) {         // normal instant power & SWR
              Tone = 1;
              PEP = 1; }
       if (MODE == 1) {        // Tone tune SWR
              Tone = 1;
              PEP = 0; }
       if (MODE == 2) {        // PEP power
              Tone = 0;
              PEP = 1; }
    
 // READ band from EEPROM
  BAND = EEPROM.read(2);
        if (BAND == 0) {         
              BAND = 3;            // No HF for time being, default = 2m
              PowCal = PowCalHF;}
        if (BAND == 1) {         
              PowCal = PowCal6m;}    
        if (BAND == 2) {         
              PowCal = PowCal4m;}
        if (BAND == 3) {         
              PowCal = PowCal2m;}    
        if (BAND == 4) {         
              PowCal = PowCal70;}
        if (BAND == 5) {         
              PowCal = PowCal23;}    
        if (BAND == 6) {         
              PowCal = PowCal13;}
           
     
// calculate max range for this band             
              
double PWRmax = pow((5000 + Diode),2) ;
PWRmax = PWRmax / PowCal / 1000;

// calculate minimum power for 'SWR < 1.5' indication threshold 

// SWR = 1.5 means PWRref / PWRFwd = 0.2
// this means that VoltFWD = diode voltage / SQRT (0.2)
       
// for threshold SWR = 3 : replace 0.45 by SQRT (0.5) = 0.71         
       
VoltFWDmini = (Diode / 0.45);
VoltFWDmini = 2* VoltFWDmini;  // safety factor, required in practice


 

// Print a message to the LCD.
  
  digitalWrite(LCDbacklight,1) ;  // turn backlight on
  lcd.setCursor(0, 0);
  lcd.print("Pwr & SWR Meter");
  lcd.setCursor(0, 1);
  lcd.print("   6m - 13cm   ");
    pinMode(TonePin, OUTPUT);
    tone(TonePin,1200);
    delay(150);
    tone(TonePin,1600);
    delay (150);
    tone(TonePin,2000);
    delay (150);
    noTone (TonePin);
    delay (2000);
    
//  lcd.setCursor(0, 1);
//  lcd.print("by ON7EQ 08/2011");  
//  delay (2000);  
  

//Power SupplyVoltage measure & display  
  measuresupplyvolt ();
  delay (1500);


  
// print max power   
  lcd.clear(); 
  
  lcd.setCursor(2, 0);
  lcd.print("QRV on");
  lcd.print( myStrings[BAND]);
  
  clearline1();
  lcd.setCursor(2, 1);
  lcd.print("Pmax = ");

// if > 1kw, 1kW is enough :o)

if (PWRmax >= 1000) {
   lcd.print(" 1 kW   "); } 

else {
    
  if (PWRmax < 1) {
   
            PowDis = PWRmax * 1000;
            if (PowDis > 100) {          //round PowDis up to ten
               PowDis = PowDis / 10;
               PowDis = PowDis * 10;
               } 
               
    //       if (PowDis < 100) {
    //            lcd.print(" ");
    //            } 
    //       if (PowDis< 10) {
    //            lcd.print(" ");
    //            } 
           lcd.print((PowDis), DEC);
           lcd.print("mW  "); 
           
  }
  
  else {
  
            PowDis = PWRmax ;
            
          //format PowDis
          
             if (PowDis > 100) {          //round PowDis up to ten
                  PowDis = PowDis / 10;
                  PowDis = PowDis * 10;
                  } 
                 
    //         if (PowDis < 100) {
    //              lcd.print(" ");
    //              } 
    //         if (PowDis< 10) {
    //              lcd.print(" ");
    //              } 
             lcd.print((PowDis), DEC);
             lcd.print("w  ");
          }
}
  delay (4000);  
  lcd.clear(); 

 // set timers
 DisplayTime = millis ();
 BacklightTime = millis ();      
             
  
} // end of setup
  
// *************************************************************       
// ***********************  L  O  O  P  ************************
// *************************************************************   

void loop() {
 
RunOnce = 0;     // Now we are in loop  
  
 // Check if mode to be cycled

if (digitalRead (ModeSwitch) == 0) {  // Mode cycle pushbutton depressed

              digitalWrite(LCDbacklight, 1) ;        // turn backlight on
              BacklightTime = millis ();  //reset timer to light LCD
                 if (beeponce == 0 ) {
                   tone(TonePin,1750);
                   delay (100);
                   tone(TonePin,1000);
                   beeponce = 1;
                   delay (20);
                 }
                 delay (50);             // give tone & debounce
                 noTone (TonePin);   
                           
                
              if (digitalRead (ModeSwitch) == 1) { // released
               
                  beeponce = 0;
                  
                          MODE = MODE + 1;  
                            if (MODE >= 3) MODE = 0;
                          
                            EEPROM.write(1,MODE);  // store new mode permanently 
                            
                            if (MODE == 0) {       // normal instant power & SWR
                              Tone = 1;
                              PEP = 1; }
                            if (MODE == 1) {       // Tone tune SWR
                              Tone = 1;
                              PEP = 0; }
                            if (MODE == 2) {       // PEP power
                              Tone = 0;
                              PEP = 1; 
                              VoltFWDmax = (0);
                              PeakTime = millis (); }
  
                              }
              }
  
  // Check if band to be cycled
  
 if (digitalRead (BANDSwitch) == 0) {                // BAND cycle pushbutton depressed

              digitalWrite(LCDbacklight, 1) ;        // turn backlight on
              BacklightTime = millis ();             //reset timer to light LCD
                 if (beepband == 0 ) {
                   tone(TonePin,1200);
                   delay(100);
                   tone(TonePin,1600);
                   delay (100);
                   tone(TonePin,2000);
                   beepband = 1;
                   delay (50);
                 }
                 delay (50);                        // give tone & debounce
                 noTone (TonePin);   
                           
                
              if (digitalRead (BANDSwitch) == 1) {   // released
               
                  beepband = 0;
                  
                          BAND = BAND + 1;  
                            
                            if (BAND >= 7) BAND = 1;    // set 0 if HF is enabled !
                          
                            EEPROM.write(2,BAND);       // store new mode permanently 
                            
                            if (BAND == 0) {            //set proper calibration constants
                                  PowCal = PowCalHF;}
                            if (BAND == 1) {         
                                  PowCal = PowCal6m;}    
                            if (BAND == 2) {         
                                  PowCal = PowCal4m;}
                            if (BAND == 3) {         
                                  PowCal = PowCal2m;}    
                            if (BAND == 4) {         
                                  PowCal = PowCal70;}
                            if (BAND == 5) {         
                                  PowCal = PowCal23;}    
                            if (BAND == 6) {         
                                  PowCal = PowCal13;}
                                  
                                  
               //show  band  
                    lcd.setCursor(11, 1);
                    lcd.print( myStrings[BAND]);
                    
                //show Pmax for this band                                
                    clearline0();
                    lcd.setCursor(0, 0);
                    lcd.print("Pmax = ");

              // calculate max range for this band             
                            
              double PWRmax = pow((5000 + Diode),2) ;
              PWRmax = PWRmax / PowCal / 1000;
              
                  // if > 1kw, 1kW is enough :o)
                  if (PWRmax >= 1000) {
                     lcd.print(" 1 kW   "); } 
                  
                  else {
                      
                    if (PWRmax < 1) {
                     
                              PowDis = PWRmax * 1000;
                              if (PowDis > 100) {          //round PowDis up to ten
                                 PowDis = PowDis / 10;
                                 PowDis = PowDis * 10;
                                 } 
                                 
                    //         if (PowDis < 100) {
                    //              lcd.print(" ");
                    //              } 
                    //         if (PowDis< 10) {
                    //              lcd.print(" ");
                    //              } 
                             lcd.print((PowDis), DEC);
                             lcd.print("mW  "); 
                             
                    }
                    
                    else {
                    
                              PowDis = PWRmax ;
                              
                            //format PowDis
                            
                               if (PowDis > 100) {          //round PowDis up to ten
                                    PowDis = PowDis / 10;
                                    PowDis = PowDis * 10;
                                    } 
                                   
                     //          if (PowDis < 100) {
                     //               lcd.print(" ");
                     //               } 
                     //          if (PowDis< 10) {
                     //               lcd.print(" ");
                     //               } 
                               lcd.print((PowDis), DEC);
                               lcd.print("w  ");
                                    }
                            }                            
                   
                   BandTime = millis();  // reset display timer for bandchange display        
                   // delay (1000);
                      }
              }
  
   
 // read sensors 

if (PushButton == 0) {             // Read 3 way switch
 Tone = digitalRead (ToneSwitch);  // read tone button
 PEP = digitalRead (PEPswitch);    // read PEP button
}


 VoltFWD = analogRead(A0);        // Read FWD sensor voltage
 VoltREF = analogRead(A1);        // Read REFL sensor voltage
 
 // PEP detect
 
 if (VoltFWD > VoltFWDmax) {  
      VoltFWDmax = VoltFWD;
      PeakTime = millis ();
      decay = 1;
       }
       
// decay

else if ((millis() - PeakTime) > 400) {  // 400 = PEP Peak hold time
              VoltFWDmax = VoltFWDmax / (decay + 0.3);
              PeakTime = millis ();
              decay = decay + 1;         //decay 
                }
      
// LCD refresh if no tone mode 
if (((millis() -  DisplayTime) > 200) and (Tone == 1)){   //200 = display refresh rate in PEP & dBm mode
    DisplayTime = millis ();
    refreshdisplay();
    }
if (Tone == 0) {                         // in tone mode, refresh triggered by tone
     decay = 0;
     refreshdisplay();
     } 
  
    
}

// =========================================================
// ************ Refresh LCD display Routine ****************
// =========================================================


void refreshdisplay () {  

 
  // check for low battery
  
   DisplayCycle = DisplayCycle ++ ;     
   
   if (DisplayCycle >= 50) {   // every 50 display cycles, check battery voltage
     DisplayCycle = (0);
     measuresupplyvolt ();
     }
   
  
  // check if band change and display to hold
  
  if (((millis() -  BandTime) < 3000)) return;  // show band change parameters
   
  
  // Check if toggle switch for mode is present, default is push button 
  
 if ((digitalRead (ToneSwitch) == 0)  or digitalRead (PEPswitch) == 0) {
   PushButton = (0);                    // toggle switch is present
 }
  
  
  // LCD Backlight
 
  if (VoltFWD>0) {  
 digitalWrite(LCDbacklight,1) ;        // turn backlight on
 BacklightTime = millis ();             //set timer 
  }
 else if (((millis() -  BacklightTime) > 8000)) {    // 8 seconds backlight
  digitalWrite(LCDbacklight, 0) ;                    // turn backlight off  
 }
  
  // Overrange detect
 
 if ((VoltFWD>1022) and (digitalRead (ModeSwitch) == 1) ) { 
   lcd.clear();
   lcd.setCursor(1, 0);
   lcd.print("- Overrange -"); 
   lcd.setCursor(2, 1);
   lcd.print("Pmax = "); 
 
  // calculate max range for this band             
                            
    double PWRmax = pow((5000 + Diode),2) ;
    PWRmax = PWRmax / PowCal / 1000;
    
    // if P > 1kw, 1kW is enough :o)
    if (PWRmax >= 1000) {
       lcd.print(" 1 kW   "); } 
    
      else {
          
        if (PWRmax < 1) {                      // We are measuring milliwatts
         
                  PowDis = PWRmax * 1000;
                  if (PowDis > 100) {          //round PowDis up to ten
                     PowDis = PowDis / 10;
                     PowDis = PowDis * 10;
                     } 
                     
                 if (PowDis < 100) {
                      lcd.print(" ");
                      } 
                 if (PowDis< 10) {
                      lcd.print(" ");
                      } 
                 lcd.print((PowDis), DEC);
                 lcd.print(" mW "); 
                 
        }
        
        else {
        
                  PowDis = PWRmax ;                      // We are measuring watts
         
                    //format PowDis
                
                   if (PowDis > 100) {                   //round PowDis up to ten
                        PowDis = PowDis / 10;
                        PowDis = PowDis * 10;
                        } 
                       
                   if (PowDis < 100) {
                        lcd.print(" ");
                        } 
                   if (PowDis< 10) {
                        lcd.print(" ");
                        } 
                   lcd.print((PowDis), DEC);
                   lcd.print(" w ");
                        }
                }                            
  
   tone(TonePin,2500);
   delay (200) ;
   noTone(TonePin);
   
   if  (digitalRead (ModeSwitch) == 1) delay (2000) ;
   lcd.clear();
   return;
}
  // process FWD voltage
  
 VoltFWD = map(VoltFWD, 0,1023,0,5000);
 VoltFWD = (VoltFWD + Diode);       //correct for diode voltage drop
 
  //process REF 

 VoltREF = map(VoltREF, 0,1023,0,5000);
 VoltREF = (VoltREF + Diode);      //correct for diode voltage drop

 
 // POWER Display
 lcd.setCursor(0, 0);
 lcd.print("Pwr "); 
 
 
 /* CALIBRATION ROUTINE FORWARD VOLTAGE  ////////////////////
 
 // This routine prints on LCD the FWD voltage measured.
 // When no power applied, the FWD voltage displayed will be the diode voltage in mV
 // To calculate the calibration factor, take the reading (including diode voltage)
 // Uncomment this routine to enter calibration mode
 
 lcd.setCursor(0, 0);
 lcd.print("VoltFWD= "); 
 lcd.print(VoltFWD, DEC);   
 delay(500);                
 
 */   //////////////////////////////////////////////////////
 
 //calcultate Power Max, we will need it later
 double PWRmax = pow((5000 + Diode),2) ;
 PWRmax = PWRmax / PowCal / 1000; 
 
 
 if (PEP == 1) {    // Instant POWER MODE
           double PWR = pow(VoltFWD,2) ;
           PWR= PWR / PowCal / 1000;
            if (VoltFWD<(Diode+2)) {
              PWR = 0;
              }
        
        if (PWRmax < 1) {               // milliwatt readout
         
             PowDis = PWR * 1000;    
                 if (PowDis < 100) {
                      lcd.print(" ");
                      } 
                 if (PowDis < 10) {
                      lcd.print(" ");
                      } 
                 lcd.print((PowDis), DEC);
                 lcd.print(" mW ");        
                if ((PWR > 0) & (Tone == 1)) {
                
                    if ((10*log10(PWR*1000)) >= 0) {lcd.print("+");} //  +  dBm
                 lcd.print(10*log10(PWR*1000)); // dBm calculation
                 }
                 else if (Tone == 1) {
                 lcd.print("(dBm)");
                   }
               if (Tone == 0) lcd.print("(Bip)");
                   
        }
        
        else {
           PowDis = PWR * 10;
       
           if (PowDis/10 < 100) {
                lcd.print(" ");
                } 
           if (PowDis/10 < 10) {
                lcd.print(" ");
                } 
           lcd.print((PowDis/10), DEC);lcd.print(".");
           lcd.print((PowDis)%10, DEC);
           lcd.print("w ");
           if ((PWR > 0) & (Tone == 1)) {
           if ((10*log10(PWR*1000)) >= 0) {lcd.print("+");} //  +  dBm
           lcd.print(10*log10(PWR*1000)); // dBm calculation
           }
           else if (Tone == 1) {
           lcd.print("(dBm)");
             }
         if (Tone == 0) lcd.print("(Bip)");
            }
           }
   
   
   
     
               
 else if (PEP == 0) {    // PEP POWER MODE
 
           Tone == 1;   // Reset Tone mode
 
             VoltPEP = map(VoltFWDmax, 0,1023,0,5000);
             VoltPEP = (VoltPEP + Diode); //correct for diode voltage
    
           double PWR = pow(VoltPEP,2) ;
           PWR= PWR / PowCal / 1000;
            if (VoltPEP<(Diode+2)) {
              PWR = 0;
              }
           
            if (PWRmax < 1) {     //milliwatt readout
        
                 PowDis = PWR * 1000;    
                 if (PowDis < 100) {
                      lcd.print(" ");
                      } 
                 if (PowDis < 10) {
                      lcd.print(" ");
                      } 
                 lcd.print((PowDis), DEC);
                 lcd.print(" mW (PEP)");     
                     
            }
            
            else {              
           PowDis = PWR * 10;
           if (PowDis/10 < 100) {
                lcd.print(" ");
                } 
           if (PowDis/10 < 10) {
                lcd.print(" ");
                } 
           lcd.print((PowDis/10), DEC);lcd.print(".");
           lcd.print((PowDis)%10, DEC);
           lcd.print("w (PEP)");
            }
               }
  
              
 // SWR Display
 
 // print the band
 
  lcd.setCursor(11, 1);
  lcd.print( myStrings[BAND]);
 
 lcd.setCursor(0, 1);
 lcd.print("SWR  "); 
 
if ((VoltFWD <= (Diode+2)) or (PEP == 0))  {    // No power = no SWR to detect
     lcd.print(" -.-  ");  
     }  
 
    else if ( (VoltFWD > (Diode+1)) & (VoltFWD < (VoltFWDmini)) & (VoltREF <= (Diode+1))){   // at low power no SWR display or < 1.5
    lcd.print("<1.5 ");
     }
  
 
 else { 
 Vratio = VoltREF / VoltFWD;
 
 // Check ROUTINE
 
 //lcd.print(VoltREF, DEC);   // DEBUG
 //lcd.print(Vratio, DEC);    // DEBUG
 
 SWR = ((1 + Vratio)/ (1 - Vratio));
 
 if ((SWR > 3.1) & (PEP == 1)) {
   lcd.print(" > 3  "); 
    tone(TonePin,2500);
    delay (60);
    noTone(TonePin);
   }
 
 else {
 SWRDis = SWR * 10;
 
 if (SWRDis < 10){    // SWR cannot be lower than 1.0
    SWRDis = 10 ;
    }

  if (SWRDis/10 < 10) {
      lcd.print(" ");
      }
 
 lcd.print((SWRDis/10), DEC);lcd.print(".");
 lcd.print((SWRDis)%10, DEC); 
 lcd.print("  ");   
   

   
 /// SWR 'Bip' MODE
  
 if ((Tone == 0) and (digitalRead (ModeSwitch) == 1)) {
        SWRtonePitch = map((SWRDis*SWRDis),100,900,300,2200); 
        SWRtoneLenght = map((SWRDis*SWRDis),100,900,300,60); 
        tone(TonePin,SWRtonePitch);
        delay (SWRtoneLenght);
        noTone(TonePin);
       }

}
}    

if ((Tone == 0) and (digitalRead (ModeSwitch) == 1)){
  delay (SWRtoneLenght/3);       // leave silence between SWR beeps, only if no mode change required
 }
}


void clearline0 () {            // subroutine clear top line display
  lcd.setCursor(0, 0);
  lcd.print("                "); 
}

void clearline1 () {            // subroutine clear bottom line display
  lcd.setCursor(0, 1);
  lcd.print("                "); 
}

void measuresupplyvolt () {    // Power SupplyVoltage measure

 SupplyVoltage = analogRead(A5);        // Read power supply voltage
 SupplyVoltage = map(SupplyVoltage, 0,1023,0,(50*(R2+R1)/R1));
 if (SupplyVoltage <= 50) return;       // not running on batteries !
 if (SupplyVoltage >= 84) SupplyVoltage=SupplyVoltage+6 ;   // running on ext power, correct for diode voltage drop 0.6v 
 
// print power supply voltage if startup or low battery condition
 
 if ((RunOnce == 1)  or  (SupplyVoltage <= VoltSupplyMini))   {
 
        lcd.clear(); 
        
        lcd.setCursor(0, 0);
        lcd.print("Batt Volt=");  
               if (SupplyVoltage < 100) {
                 lcd.print(" ");
                      } 
                 if (SupplyVoltage < 10) {
                      lcd.print(" ");
                      } 
                 lcd.print((SupplyVoltage/10), DEC);
                     lcd.print(".");
                 lcd.print((SupplyVoltage)%10, DEC); 
                      lcd.print("v");
        if   (SupplyVoltage  <= VoltSupplyMini) {           
          lcd.setCursor(2, 1);                 
          lcd.print("LOW BATTERY !");
        }
        delay (1500);
       }    
  
}