diff --git a/src/wspr.c b/src/wspr.c
--- a/src/wspr.c
+++ b/src/wspr.c
@@ -4,6 +4,7 @@
 #include "gpio.h"
 #include "wspr.h"
 #include "i2c.h"
+#include "gps.h"
 #include "config.h"
 
 
@@ -11,9 +12,13 @@
 #define WSPR_TONE_SPACING 146 // ~1.46 Hz
 #define WSPR_CTC 10672 // CTC value for WSPR
 
+char call_orig[7] = "KD8TDF";
+#define DBM_ORIG 10
+
+
 // Test stuff
 char call[7] = "KD8TDF";
-char loc[5] = "EN72";
+char loc[5] = "EN82";
 uint8_t dbm = 10;
 uint8_t tx_buffer[255];
 
@@ -48,13 +53,158 @@ void wspr_wakeup(void)
 
 
 // Bring up TCXO and oscillator IC
-void wspr_transmit(uint8_t* grid_locator)
+void wspr_transmit(uint8_t* grid_locator, uint8_t send_alternate)
 {
 	// Copy 4 digit grid locator to local buffer; null terminate
 	for(uint8_t i=0; i<4; i++)
 		loc[i] = grid_locator[i];
 	loc[4] = '\0';
 
+    // Set power to altitude in m / 150
+    uint8_t altscaled = gps_getdata()->altitude / 150;
+    if(altscaled > 60)
+        altscaled = 60;
+
+
+    // If alternate packet, send 0XFXXEN82XX
+    if(send_alternate)
+    {
+
+
+
+        /////////////////////////////////////////////////
+        // Composite altitude and sub-maidenhead locator
+        ///////////////////////////////////////////////// 
+        uint16_t maiden_ext = (loc[4] - 'A') + ((loc[5] - 'A') * 24); // 0-575
+        uint16_t altitude_mod = gps_getdata()->altitude / 20;   
+
+        // Ciel at 21,340 meters
+        if(altitude_mod > 1067)
+            altitude_mod = 1067; // Don't overflow into maidenhead!
+    
+        // Compose composite altitude (lsbs) with maidenhead locator (msbs)
+        uint32_t subalt = (1068 * maiden_ext) + (gps_getdata()->altitude / 20);
+
+
+
+        ////////////////////////////////////////////
+        // Encode extended maidenhead and altitude
+        ////////////////////////////////////////////
+        call[0] = '0';
+
+        // Split into chunks of valmax 36, 26, 26, 26
+
+        // Mask off following 3 26valmax fields
+        uint32_t chunk = subalt / 26 / 26 / 26; 
+
+        // Encode to callsign
+        if(chunk < 10)
+            call[1] = '0' + chunk
+        else
+            call[1] = chunk - 10 + 'A';
+
+        // Subtract off previous portion
+        subalt -= (chunk * 26 * 26 * 26);
+
+        // Mask off following 2 26bit values
+        chunk = (subalt / 26 / 26);
+
+        call[3] = 'A' + chunk;
+
+        // Subtract off previous portion
+        subalt -= (chunk * 26 * 26)
+
+        // Mask off following 1 26bit values
+        chunk = (subalt / 26);
+
+        call[4] = 'A' + chunk;
+
+        // Subtract off previous portion
+        subalt -= (chunk * 26);
+
+        // Remainder is the last call char
+        call[5] = 'A' + subalt;
+ 
+
+        ////////////////////////////////////////
+        // Composite temp/batt/speed/gps 
+        ////////////////////////////////////////
+
+        // Encode value from -50C to 39C => 0-89. TODO: Bounds!
+        uint8_t temp_enc = 0 + 50;
+
+        // Encode value from 0-39 with some scalar/offset/etc
+        uint8_t batt_enc = 0; 
+
+        // Encode speed in knots from 0-82 to 0-41
+        uint8_t speed_enc = gpsdata()->speed / 2;
+        if(speed_enc > 41)
+            speed_enc = 41;
+
+        // Encode GPS status
+        uint8_t gps_status = 0b00; // MSB is valid fix, lsb is sats > 8
+
+        uint32_t engdata = gps_status + 2 * (speed_enc + 42 * (batt_enc + 40 * temp_enc));
+
+        ////////////////////////////////////////////
+        // Encode temp/batt/speed/gps
+        ////////////////////////////////////////////
+
+        // Mask off fields
+        chunk = engdata / 18 / 10 / 10 / 19;  
+
+        // Encode to grid locator
+        grid_locator[0] = 'A' + chunk;
+
+        // Subtract off previous portion 
+        engdata -= (chunk * 18 * 10 * 10 * 19);  
+
+        // Mask of fields
+        chunk = engdata / 10 / 10 / 19;  
+
+        // Encode to grid locator
+        grid_locator[1] = 'A' + chunk;
+
+        // Subtract off previous portion
+        engdata -= (chunk * 10 * 10 * 19);  
+
+        // Mask off fields
+        chunk = engdata / 10 / 19;  
+
+        // Encode
+        grid_locater[2] = '0' + chunk;
+
+        // Subtract
+        engdata -= (chunk * 10 * 19);  
+
+        // Mask off
+        chunk = engdata / 19;  
+
+        // Encode
+        grid_locator[3] = chunk;
+
+        // Subtract
+        engdata -= (chunk * 19);  
+
+        // Mask off
+        chunk = engdata;  
+
+        // Encode
+        uint8_t powers[] = {0, 3, 7, 10, 13, 17, 20, 23, 27, 30, 33, 37, 40, 43, 47, 50, 53, 57, 60}
+        dbm = powers[chunk];
+    }
+    else
+    {
+        call[0] = call_orig[0];
+        call[1] = call_orig[1];
+        call[2] = call_orig[2];
+        call[3] = call_orig[3];
+        call[4] = call_orig[4];
+        call[5] = call_orig[5];
+        call[6] = call_orig[6];
+
+        dbm = DBM_ORIG; 
+    }
 
     // Start timer for WSPR
     __TIM1_CLK_ENABLE();