diff --git a/tracker/software/cfg/pp10a/portab.c b/tracker/software/cfg/pp10a/portab.c
index 2d84f721..b6918159 100644
--- a/tracker/software/cfg/pp10a/portab.c
+++ b/tracker/software/cfg/pp10a/portab.c
@@ -41,20 +41,20 @@ const si446x_mcucfg_t radio1_cfg = {
 		.nirq	= LINE_RADIO_NIRQ,
 		.sdn	= LINE_RADIO_SDN,
 		.cs		= LINE_RADIO_CS,
-		.spi	= PKT_RADIO_SPI,
+		.spi	= PKT_RADIO1_SPI,
         .icu    = RADIO1_ICU_DRIVER,
         .alt    = (PAL_MODE_INPUT | PAL_MODE_ALTERNATE(2)),
         .cfg    =  {
                       ICU_INPUT_ACTIVE_HIGH,
-                      ICU_COUNT_FREQUENCY,          /* ICU clock frequency. */
+                      ICU_COUNT_FREQUENCY,      /**< ICU clock frequency. */
                     #if LINE_PWM_MIRROR != PAL_NOLINE
-                      pktRadioICUWidth,             /* ICU width callback. */
+                      pktRadioICUWidth,         /**< ICU width callback. */
                     #else
-                      NULL,                         /* ICU width callback. */
+                      NULL,                     /**< ICU width callback. */
                     #endif
-                      pktRadioICUPeriod,            /* ICU period callback. */
-                      pktRadioICUOverflow,          /* ICU overflow callback. */
-                      ICU_CHANNEL_1,                /* Timer channel 0. */
+                      pktRadioICUPeriod,        /**< ICU period callback. */
+                      pktRadioICUOverflow,      /**< ICU overflow callback. */
+                      ICU_CHANNEL_1,            /**< Timer channel. */
                       0
                     }
 };
@@ -67,17 +67,20 @@ si446x_data_t radio1_dat = {
          */
 };
 
+/* List of bands in this radio. */
+const radio_band_t *const radio_bands[] = {
+                (radio_band_t *const)&band_2m,
+                 NULL
+};
+
 /* Radios on this board. */
 const radio_config_t radio_list[] = {
   { /* Radio #1 */
     .unit = PKT_RADIO_1,
     .type = SI446X,
-	.cfg	= (si446x_mcucfg_t * const)&radio1_cfg,
+	.cfg	= (si446x_mcucfg_t *const)&radio1_cfg,
     .dat    = (si446x_data_t *)&radio1_dat,
-    .bands  = {
-             (radio_band_t * const)&band_2m,
-              NULL
-            }
+    .bands  = (radio_band_t **const)radio_bands
   }, /* End radio1 */
   {
      .unit = PKT_RADIO_NONE
diff --git a/tracker/software/cfg/pp10a/portab.h b/tracker/software/cfg/pp10a/portab.h
index da74b0b9..a006e090 100644
--- a/tracker/software/cfg/pp10a/portab.h
+++ b/tracker/software/cfg/pp10a/portab.h
@@ -18,17 +18,15 @@
  */
 #define SERIAL_CFG_DEBUG_DRIVER		&SD3
 
-//#define USE_SPI_ATTACHED_RADIO      TRUE
-
 /*
- * TODO: Need to use radio unit ID to set assigned GPIO & SPI.
- * Only if there is a multi radio board...
+ * SPI definitions
  */
+#define SPI_BUS1_DRIVER             &SPID3
 
 /*
  * Radio SPI definitions.
  */
-#define PKT_RADIO_SPI               &SPID3
+#define PKT_RADIO1_SPI              SPI_BUS1_DRIVER
 
 // Camera pins
 #define LINE_CAM_XCLK               PAL_LINE(GPIOC, 9U)
@@ -109,6 +107,7 @@
 #define LINE_SPI_MISO               PAL_LINE(GPIOB, 4U)
 #define LINE_SPI_MOSI               PAL_LINE(GPIOB, 5U)
 
+/* TODO: Move into pktradio.h */
 #define BAND_MIN_2M_FREQ	    	144000000				/* Minimum allowed frequency in Hz */
 #define BAND_MAX_2M_FREQ			148000000				/* Maximum allowed frequency in Hz */
 #define BAND_STEP_2M_HZ             12500
@@ -119,13 +118,16 @@
 #define BAND_DEF_70CM_APRS          439100000               /* Default frequency in Hz.        */
 
 #define DEFAULT_OPERATING_FREQ      144800000
+#if DEFAULT_OPERATING_FREQ < BAND_MIN_2M_FREQ
+#error "Default operating frequency must be an absolute in Hz"
+#endif
 
 /* Si446x clock setup. */
 #define Si446x_CLK					STM32_HSECLK			/* Oscillator frequency in Hz */
 #define Si446x_CLK_OFFSET			22						/* Oscillator frequency drift in ppm */
 #define Si446x_CLK_TCXO_EN			true					/* Set this true, if a TCXO is used, false for XTAL */
 
-#define NUM_BANDS_PER_RADIO         2
+//#define NUM_BANDS_PER_RADIO         2
 
 /* LED status indicators (set to PAL_NOLINE if not available). */
 #define LINE_OVERFLOW_LED           PAL_NOLINE
@@ -246,14 +248,6 @@
 /* Module data structures and types.                                         */
 /*===========================================================================*/
 
-typedef struct radioConfig {
-  radio_unit_t  unit;
-  radio_type_t  type;
-  void			*cfg;
-  void          *dat;
-  radio_band_t  *bands[NUM_BANDS_PER_RADIO];
-} radio_config_t;
-
 /*===========================================================================*/
 /* Module macros.                                                            */
 /*===========================================================================*/
diff --git a/tracker/software/cfg/pp10b/portab.c b/tracker/software/cfg/pp10b/portab.c
index 8a28c4ec..8eca4679 100644
--- a/tracker/software/cfg/pp10b/portab.c
+++ b/tracker/software/cfg/pp10b/portab.c
@@ -41,7 +41,7 @@ const si446x_mcucfg_t radio1_cfg = {
 		.nirq	= LINE_RADIO_NIRQ,
 		.sdn	= LINE_RADIO_SDN,
 		.cs		= LINE_RADIO_CS,
-        .spi    = PKT_RADIO_SPI,
+        .spi    = PKT_RADIO1_SPI,
 		.icu    = RADIO1_ICU_DRIVER,
 		.alt    = (PAL_MODE_INPUT | PAL_MODE_ALTERNATE(2)),
 		.cfg    = {
@@ -64,21 +64,25 @@ si446x_data_t radio1_dat = {
         // TODO: Move part and func structs into here and add functions to get
 };
 
-/* Array of radios on this board. */
+
+/* List of bands in this radio. */
+const radio_band_t *const radio_bands[] = {
+                (radio_band_t *const)&band_2m,
+                 NULL
+};
+
+/* Radios on this board. */
 const radio_config_t radio_list[] = {
   { /* Radio #1 */
     .unit = PKT_RADIO_1,
     .type = SI446X,
-	.cfg	= (si446x_mcucfg_t * const)&radio1_cfg,
-	.dat    = (si446x_data_t *)&radio1_dat,
-    .bands  = {
-             (radio_band_t * const)&band_2m,
-              NULL
-            }
+    .cfg    = (si446x_mcucfg_t *const)&radio1_cfg,
+    .dat    = (si446x_data_t *)&radio1_dat,
+    .bands  = (radio_band_t **const)radio_bands
   }, /* End radio1 */
   {
      .unit = PKT_RADIO_NONE
-  } /* End radios. */
+  }
 };
 
 /**
diff --git a/tracker/software/cfg/pp10b/portab.h b/tracker/software/cfg/pp10b/portab.h
index c8d67d44..81ebfd18 100644
--- a/tracker/software/cfg/pp10b/portab.h
+++ b/tracker/software/cfg/pp10b/portab.h
@@ -23,10 +23,15 @@
  * Only if there is a multi radio board...
  */
 
+/*
+ * SPI definitions
+ */
+#define SPI_BUS1_DRIVER             &SPID3
+
 /*
  * Radio SPI definitions.
  */
-#define PKT_RADIO_SPI               &SPID3
+#define PKT_RADIO1_SPI              SPI_BUS1_DRIVER
 
 // Camera pins
 #define LINE_CAM_XCLK               PAL_LINE(GPIOC, 9U)
@@ -108,6 +113,7 @@
 #define LINE_SPI_MISO               PAL_LINE(GPIOB, 4U)
 #define LINE_SPI_MOSI               PAL_LINE(GPIOB, 5U)
 
+/* TODO: Move into pktradio.h */
 #define BAND_MIN_2M_FREQ            144000000               /* Minimum allowed frequency in Hz */
 #define BAND_MAX_2M_FREQ            148000000               /* Maximum allowed frequency in Hz */
 #define BAND_STEP_2M_HZ             12500
@@ -118,13 +124,16 @@
 #define BAND_DEF_70CM_APRS          439100000               /* Default frequency in Hz.        */
 
 #define DEFAULT_OPERATING_FREQ      144800000
+#if DEFAULT_OPERATING_FREQ < BAND_MIN_2M_FREQ
+#error "Default operating frequency must be an absolute in Hz"
+#endif
 
 /* Si446x clock setup. */
 #define Si446x_CLK					STM32_HSECLK			/* Oscillator frequency in Hz */
 #define Si446x_CLK_OFFSET			22						/* Oscillator frequency drift in ppm */
 #define Si446x_CLK_TCXO_EN			true					/* Set this true, if a TCXO is used, false for XTAL */
 
-#define NUM_BANDS_PER_RADIO         2
+//#define NUM_BANDS_PER_RADIO         2
 
 /* LED status indicators (set to PAL_NOLINE if not available). */
 #define LINE_OVERFLOW_LED           PAL_NOLINE
@@ -243,14 +252,6 @@
 /* Module data structures and types.                                         */
 /*===========================================================================*/
 
-typedef struct radioConfig {
-  radio_unit_t  unit;
-  radio_type_t  type;
-  void 			*cfg;
-  void          *dat;
-  radio_band_t  *bands[NUM_BANDS_PER_RADIO];
-} radio_config_t;
-
 /*===========================================================================*/
 /* Module macros.                                                            */
 /*===========================================================================*/
diff --git a/tracker/software/make/pp10a.make b/tracker/software/make/pp10a.make
index a311e623..81582381 100644
--- a/tracker/software/make/pp10a.make
+++ b/tracker/software/make/pp10a.make
@@ -216,8 +216,8 @@ CPPWARN = -Wall -Wextra -Wundef
 # List all user C define here, like -D_DEBUG=1
 UDEFS = -D_GNU_SOURCE -DARM_MATH_CM4 -DSHELL_CMD_TEST_ENABLED=0 \
 		-DSHELL_CMD_EXIT_ENABLED=1 -DUSB_TRACE_LEVEL=5 \
-		-DSHELL_CMD_MEM_ENABLED=0
-		# -DDISABLE_HW_WATCHDOG=1
+		-DSHELL_CMD_MEM_ENABLED=0 
+		#-DDISABLE_HW_WATCHDOG=1
 
 # Define ASM defines here
 UADEFS =
diff --git a/tracker/software/source/config/config.c b/tracker/software/source/config/config.c
index 5ef24eab..4cf8b93a 100644
--- a/tracker/software/source/config/config.c
+++ b/tracker/software/source/config/config.c
@@ -55,15 +55,15 @@ const conf_t conf_flash_default = {
     // Primary image app
     .img_pri = {
         .svc_conf = {
-            .active = false,
-            .cycle = TIME_S2I(60 * 30),
+            .active = true,
+            .cycle = TIME_S2I(60 * 5),
             .init_delay = TIME_S2I(90),
-            .send_spacing = TIME_S2I(30)
+            .send_spacing = TIME_S2I(5)
         },
         .radio_conf = {
             .pwr = 0x7F,
-            .freq = APRS_FREQ_AUSTRALIA,
-            .mod = MOD_AFSK,
+            .freq = 144800000,
+            .mod = MOD_2FSK,
             .cca = 0x4F
 
         },
@@ -81,7 +81,7 @@ const conf_t conf_flash_default = {
     // Secondary image app
     .img_sec = {
         .svc_conf = {
-            .active = false,
+            .active = true,
             .cycle = TIME_S2I(60 * 15),
             .init_delay = TIME_S2I(60 * 1),
             .send_spacing = TIME_S2I(30)
diff --git a/tracker/software/source/drivers/ov5640.c b/tracker/software/source/drivers/ov5640.c
index 3e61ddbd..143364a0 100644
--- a/tracker/software/source/drivers/ov5640.c
+++ b/tracker/software/source/drivers/ov5640.c
@@ -983,13 +983,14 @@ void vsync_cb(void *arg) {
  * Other drivers using resources that can cause DMA competition are locked.
  */
 msg_t OV5640_LockResourcesForCapture(void) {
-
+  /* TODO: have to make this a loop which would handle multiple receivers. */
+  /* Acquire radio after any TX completes. */
   msg_t msg = pktAcquireRadio(PKT_RADIO_1, TIME_INFINITE);
   if(msg != MSG_OK) {
     return msg;
   }
   I2C_Lock();
-  /* TODO: have to make this a loop which would handle multiple receivers. */
+
   pktLLDradioPauseDecoding(PKT_RADIO_1);
   //pktPauseDecoding(PKT_RADIO_1);
   /* Hold TRACE output on USB. */
@@ -1009,9 +1010,13 @@ void OV5640_UnlockResourcesForCapture(void) {
   /* TODO: have to make this a loop which would handle multiple receivers. */
   pktLLDradioResumeDecoding(PKT_RADIO_1);
   //pktResumeDecoding(PKT_RADIO_1);
+  /* Enable TX tasks to run. */
   pktReleaseRadio(PKT_RADIO_1);
 }
 
+/**
+ *
+ */
 uint32_t OV5640_Capture(uint8_t* buffer, uint32_t size) {
 
 	/*
@@ -1030,8 +1035,8 @@ uint32_t OV5640_Capture(uint8_t* buffer, uint32_t size) {
 	dma_capture_t dma_control = {0};
 
 	/* Setup DMA for transfer on timer CC tigger.
-	 * For TIM8 this DMA2 stream 2, channel 7.
-	 * Use PL 3 as PCLCK rate is high.
+	 * For TIM8 this is DMA2 stream 2, channel 7.
+	 * Use PL 3 as camera PCLK rate is high and we need priority service.
 	 */
 	dma_control.dmastp  = STM32_DMA_STREAM(STM32_DMA_STREAM_ID(2, 2));
 	uint32_t dmamode = STM32_DMA_CR_CHSEL(7) |
diff --git a/tracker/software/source/drivers/sd.c b/tracker/software/source/drivers/sd.c
index e8e35893..53e77e8c 100644
--- a/tracker/software/source/drivers/sd.c
+++ b/tracker/software/source/drivers/sd.c
@@ -39,10 +39,10 @@ bool initSD(void)
 	};
 
 	// MMC/SD over SPI driver configuration
-	static MMCConfig mmccfg = {&SPID3, &ls_spicfg, &hs_spicfg};
+	static MMCConfig mmccfg = {SPI_BUS1_DRIVER, &ls_spicfg, &hs_spicfg};
 
 	// Check SD card presence
-	spiAcquireBus(&SPID3);
+	spiAcquireBus(SPI_BUS1_DRIVER);
 
 	// Init MMC
 	mmcObjectInit(&MMCD1);
@@ -55,7 +55,7 @@ bool initSD(void)
 		TRACE_INFO("SD   > SD card connection OK");
 		sdInitialized = true;
 	}
-	spiReleaseBus(&SPID3);
+	spiReleaseBus(SPI_BUS1_DRIVER);
 
 	return sdInitialized;
 }
@@ -65,7 +65,7 @@ bool writeBufferToFile(const char *filename, const uint8_t *buffer, uint32_t len
 	if(!sdInitialized)
 		return false;
 
-	spiAcquireBus(&SPID3);
+	spiAcquireBus(SPI_BUS1_DRIVER);
 
 	static FATFS fs;
 	static FIL fdst;
@@ -125,7 +125,7 @@ bool writeBufferToFile(const char *filename, const uint8_t *buffer, uint32_t len
 		}
 	}
 
-	spiReleaseBus(&SPID3);
+	spiReleaseBus(SPI_BUS1_DRIVER);
 
 	return gres;
 }
diff --git a/tracker/software/source/drivers/si446x_patch.h b/tracker/software/source/drivers/si4463_patch.h
similarity index 94%
rename from tracker/software/source/drivers/si446x_patch.h
rename to tracker/software/source/drivers/si4463_patch.h
index 97734e8c..603d5a56 100644
--- a/tracker/software/source/drivers/si446x_patch.h
+++ b/tracker/software/source/drivers/si4463_patch.h
@@ -10,10 +10,10 @@
 // SIZE=512
 // CRCT=0x714b
 
-#define SI446X_PATCH_ROMID  00
-#define SI446X_PATCH_ID     00
+#define SI4463_PATCH_ROMID  0x06
+#define SI4463_PATCH_ID     0xCA90
 
-#define SI446X_PATCH_CMDS                   \
+#define SI4463_PATCH_CMDS                   \
 0x08,0x04,0x21,0x71,0x4B,0x00,0x00,0xDC,0x95, \
 0x08,0x05,0xA6,0x22,0x21,0xF0,0x41,0x5B,0x26, \
 0x08,0xE2,0x2F,0x1C,0xBB,0x0A,0xA8,0x94,0x28, \
diff --git a/tracker/software/source/drivers/si446x.c b/tracker/software/source/drivers/si446x.c
index 32e60640..3d4af120 100644
--- a/tracker/software/source/drivers/si446x.c
+++ b/tracker/software/source/drivers/si446x.c
@@ -5,30 +5,20 @@
  */
 
 #include "pktconf.h"
-#ifndef PKT_IS_TEST_PROJECT
 #include "debug.h"
-#endif
-
-#ifndef PKT_IS_TEST_PROJECT
 #include "radio.h"
-#endif
-
 #include "geofence.h"
-#include "si446x_patch.h"
+#include "si4463_patch.h"
 
 
 /*===========================================================================*/
 /* Module local variables.                                                   */
 /*===========================================================================*/
 
-/* TODO: Has to move into radio data struct. */
-//static int16_t lastTemp = 0x7FFF;
-
 /*===========================================================================*/
 /* Module constants.                                                         */
 /*===========================================================================*/
 
-
 /*===========================================================================*/
 /* Module exported variables.                                                */
 /*===========================================================================*/
@@ -37,8 +27,8 @@
 /* Module local definitions.                                                 */
 /*===========================================================================*/
 
-static const uint8_t Radio_Patch_Data_Array[] = {
-        SI446X_PATCH_CMDS,
+static const uint8_t Si4463_Patch_Data_Array[] = {
+        SI4463_PATCH_CMDS,
         0x00
  };
 
@@ -81,7 +71,7 @@ static SPIDriver *Si446x_spiSetupBus(const radio_unit_t radio,
 /**
  * SPI write which uses CTS presented on radio GPIO1.
  * Used when starting the radio up from shutdown state.
- * @pre The MCU GPIO pin connected to 446x GPIO1 must be pre-configured.
+ * @pre The MCU GPIO pin connected to 446x GPIO1 must be configured as input.
  */
 static bool Si446x_writeBoot(const radio_unit_t radio,
                              const uint8_t* txData, uint32_t len) {
@@ -91,7 +81,7 @@ static bool Si446x_writeBoot(const radio_unit_t radio,
   SPIDriver *spip = Si446x_spiSetupBus(radio, &ls_spicfg);
   spiStart(spip, &ls_spicfg);
 
-  /* Poll for CTS. */
+  /* Poll for CTS with timeout of 100mS. */
   ioline_t cts = Si446x_getConfig(radio)->gpio1;
   uint8_t timeout = 100;
   do {
@@ -107,7 +97,7 @@ static bool Si446x_writeBoot(const radio_unit_t radio,
     return false;
   }
 
-  /* Transfer data. No need to check CTS.*/
+  /* Transfer data now there is CTS.*/
   spiSelect(spip);
   spiSend(spip, len, txData);
   spiUnselect(spip);
@@ -131,7 +121,7 @@ static bool Si446x_write(const radio_unit_t radio,
     SPIDriver *spip = Si446x_spiSetupBus(radio, &ls_spicfg);
     spiStart(spip, &ls_spicfg);
 
-    /* Poll for CTS. */
+    /* Poll for CTS with timeout of 100mS. */
     uint8_t timeout = 100;
     uint8_t rx_ready[] = {Si446x_READ_CMD_BUFF, 0x00};
     do {
@@ -174,7 +164,7 @@ static bool Si446x_readBoot(const radio_unit_t radio,
     /* Acquire bus and get SPI Driver object. */
     SPIDriver *spip = Si446x_spiSetupBus(radio, &ls_spicfg);
 
-    /* Poll for CTS on GPIO1 from radio. */
+    /* Poll for CTS with timeout of 100mS. */
     ioline_t cts = Si446x_getConfig(radio)->gpio1;
     uint8_t timeout = 100;
     while(palReadLine(cts) != PAL_HIGH && timeout--) {
@@ -238,6 +228,7 @@ static bool Si446x_read(const radio_unit_t radio,
      * Poll command buffer waiting for CTS from the READ_CMD_BUFF command.
      * This command does not itself cause CTS to report busy.
      * Allocate a buffer to use for CTS check.
+     * Timeout after 100mS waiting for CTS.
      */
     uint8_t timeout = 100;
     uint8_t rx_ready[] = {Si446x_READ_CMD_BUFF, 0x00};
@@ -268,6 +259,7 @@ static bool Si446x_read(const radio_unit_t radio,
      * Poll waiting for CTS again using the READ_CMD_BUFF command.
      * Once CTS is received the response data is ready in the rx data buffer.
      * The buffer contains the command, CTS and 0 - 16 bytes of response.
+     * Timeout after 100mS waiting for CTS.
      */
     timeout = 100;
     do {
@@ -399,10 +391,10 @@ static bool Si446x_init(const radio_unit_t radio) {
     chThdSleep(TIME_MS2I(10));
     Si446x_radioStartup(radio);
     uint16_t i = 0;
-    while(Radio_Patch_Data_Array[i] != 0) {
-      Si446x_writeBoot(radio, &Radio_Patch_Data_Array[i + 1],
-                       Radio_Patch_Data_Array[i]);
-      i += Radio_Patch_Data_Array[i] + 1;
+    while(Si4463_Patch_Data_Array[i] != 0) {
+      Si446x_writeBoot(radio, &Si4463_Patch_Data_Array[i + 1],
+                       Si4463_Patch_Data_Array[i]);
+      i += Si4463_Patch_Data_Array[i] + 1;
     }
     const uint8_t init_command[] = {Si446x_POWER_UP, 0x81,
                                     (Si446x_CLK_TCXO_EN & 0x1),
@@ -573,12 +565,17 @@ bool Si446x_conditional_init(const radio_unit_t radio) {
 
 /*
  * Set radio NCO registers for frequency.
- * This function also collects the chip temperature data.
+ * This function also collects the chip temperature data at the moment.
+ * TODO: Move temperature reading to???
  */
 bool Si446x_setBandParameters(const radio_unit_t radio,
                               radio_freq_t freq,
                               channel_hz_t step) {
 
+  /*
+   * TODO: The driver should not check for DYNAMIC.
+   * All frequencies passed to radio should be absolute.
+   */
   if(freq == FREQ_APRS_DYNAMIC) {
     /* Get transmission frequency by geofencing. */
       freq = getAPRSRegionFrequency();
@@ -949,6 +946,7 @@ static bool Si446x_transmit(const radio_unit_t radio,
                             radio_squelch_t rssi,
                             sysinterval_t cca_timeout) {
 
+  /* Get an absolute operating frequency in Hz. */
   radio_freq_t op_freq = pktComputeOperatingFrequency(radio, freq,
                                                       step, chan, RADIO_TX);
 
@@ -1087,11 +1085,12 @@ bool Si4464_resumeReceive(const radio_unit_t radio,
                           mod_t rx_mod) {
   bool ret = true;
 
+  /* Get an absolute operating frequency in Hz. */
   radio_freq_t op_freq = pktComputeOperatingFrequency(radio,
                                                       rx_frequency,
-                                                        rx_step,
-                                                        rx_chan,
-                                                        RADIO_RX);
+                                                      rx_step,
+                                                      rx_chan,
+                                                      RADIO_RX);
 
 
   TRACE_INFO( "SI   > Enable reception %d.%03d MHz (ch %d),"
@@ -1168,7 +1167,9 @@ static uint8_t Si446x_getUpsampledNRZIbits(up_sampler_t *upsampler,
  */
 static void Si446x_transmitTimeoutI(thread_t *tp) {
   /* Tell the thread to terminate. */
-  chEvtSignal(tp, SI446X_EVT_TX_TIMEOUT);
+  chSysLockFromISR();
+  chEvtSignalI(tp, SI446X_EVT_TX_TIMEOUT);
+  chSysUnlockFromISR();
 }
 
 /*
@@ -1201,6 +1202,7 @@ THD_FUNCTION(bloc_si_fifo_feeder_afsk, arg) {
   /* Initialize radio. */
   Si446x_conditional_init(radio);
 
+  /* Base frequency is an absolute frequency in Hz. */
   Si446x_setBandParameters(radio, rto->base_frequency,
                            rto->step_hz);
 
@@ -1459,6 +1461,7 @@ THD_FUNCTION(bloc_si_fifo_feeder_fsk, arg) {
   /* Set 446x back to READY from RX (if active). */
   Si446x_pauseReceive(radio);
 
+  /* Base frequency is an absolute frequency in Hz. */
   Si446x_setBandParameters(radio, rto->base_frequency, rto->step_hz);
 
   /* Set parameters for 2FSK transmission. */
diff --git a/tracker/software/source/math/geofence.c b/tracker/software/source/math/geofence.c
index 7b6a1065..9fb6988e 100644
--- a/tracker/software/source/math/geofence.c
+++ b/tracker/software/source/math/geofence.c
@@ -658,7 +658,9 @@ uint32_t getAPRSRegionFrequency() {
 
 	// Position unknown
 	if(point == NULL || (point->gps_lat == 0 && point->gps_lon == 0))
-		return conf_sram.freq;
+		//return conf_sram.freq;
+	  // Return code and let pktradio figure out what to do.
+	  return FREQ_APRS_DEFAULT;
 	
 	// America 144.390 MHz
 	if(isPointInAmerica(point->gps_lat, point->gps_lon))
diff --git a/tracker/software/source/pkt/channels/rxpwm.c b/tracker/software/source/pkt/channels/rxpwm.c
index ca95b662..49cb29a0 100644
--- a/tracker/software/source/pkt/channels/rxpwm.c
+++ b/tracker/software/source/pkt/channels/rxpwm.c
@@ -207,7 +207,7 @@ void pktDisableRadioPWM(const radio_unit_t radio) {
   /*
    * Reschedule is required to avoid a "priority order violation".
    * TODO: Investigate the iclass time used.  Might be systick related? */
-  chSchRescheduleS();
+  //chSchRescheduleS();
   chSysUnlock();
 }
 
@@ -449,7 +449,10 @@ void pktOpenPWMChannelI(ICUDriver *myICU, eventflags_t evt) {
  * @api
  */
 void pktSleepICUI(ICUDriver *myICU) {
-  /* All we do is stop capture. */
+  /**
+   * Each ICU instance is attached to only one radio.
+   * All we do is stop the capture for that ICU instance.
+   */
   icuStopCaptureI(myICU);
 }
 
@@ -464,9 +467,10 @@ void pktSleepICUI(ICUDriver *myICU) {
  */
 void pktICUInactivityTimeout(ICUDriver *myICU) {
 
-  /* This will stop ICU to save power.
+  /*
    * The ICU notifications are enabled and disabled during normal operation.
-   * This timer will shutdown the ICU timer after an idle period.
+   * This timer shuts down the ICU timer after an idle period.
+   * This saves a (probably insignificant) amount of MCU power.
    */
   chSysLockFromISR();
   AFSKDemodDriver *myDemod = myICU->link;
@@ -527,7 +531,7 @@ void pktRadioCCALeadTimer(ICUDriver *myICU) {
   switch(cca) {
     case PAL_LOW: {
         /*
-         * CAA has dropped so it is a spike.
+         * CAA has dropped so it is a spike which is ignored.
          */
       pktAddEventFlagsI(myHandler, EVT_RADIO_CCA_SPIKE);
       break;
@@ -635,6 +639,7 @@ void pktRadioCCAInput(ICUDriver *myICU) {
   return;
 }
 
+#if LINE_PWM_MIRROR != PAL_NOLINE
 /**
  * @brief   Width callback from ICU driver.
  * @notes   Called at ISR level.
@@ -647,6 +652,7 @@ void pktRadioICUWidth(ICUDriver *myICU) {
   (void)myICU;
   pktWriteGPIOline(LINE_PWM_MIRROR, PAL_LOW);
 }
+#endif
 
 /**
  * @brief   Period callback from ICU driver.
diff --git a/tracker/software/source/pkt/managers/pktradio.c b/tracker/software/source/pkt/managers/pktradio.c
index 9528abf4..456a6acc 100644
--- a/tracker/software/source/pkt/managers/pktradio.c
+++ b/tracker/software/source/pkt/managers/pktradio.c
@@ -15,9 +15,8 @@
  */
 
 #include "pktconf.h"
-#ifndef PKT_IS_TEST_PROJECT
 #include "radio.h"
-#endif
+
 #include "si446x.h"
 #include "debug.h"
 #include "geofence.h"
@@ -30,14 +29,14 @@ const radio_band_t band_2m = {
   .start    = BAND_MIN_2M_FREQ,
   .end      = BAND_MAX_2M_FREQ,
   .step     = BAND_STEP_2M_HZ,
-  .def_aprs = BAND_DEF_2M_APRS
+  //.def_aprs = BAND_DEF_2M_APRS
 };
 
 const radio_band_t band_70cm = {
   .start    = BAND_MIN_70CM_FREQ,
   .end      = BAND_MAX_70CM_FREQ,
   .step     = BAND_STEP_70CM_HZ,
-  .def_aprs = BAND_DEF_70CM_APRS
+  //.def_aprs = BAND_DEF_70CM_APRS
 };
 
 /**
@@ -54,7 +53,7 @@ const radio_band_t band_70cm = {
  * @notapi
  */
 THD_FUNCTION(pktRadioManager, arg) {
-  /* When waiting for TX tasks to complete. */
+  /* When waiting for TX tasks to complete if manager is terminating. */
 #define PKT_RADIO_TX_TASK_RECHECK_WAIT_MS     100
 
   packet_svc_t *handler = arg;
@@ -708,7 +707,10 @@ int pktDisplayFrequencyCode(const radio_freq_t code, char *buf, size_t size) {
 }
 
 /**
- * @brief   Get default operating frequency.
+ * @brief   Get a default operating frequency.
+ * @notes   If a valid default is set in configuration use it
+ * @notes   Else if a valid frequency is in the radio configuration use it
+ * @notes   Else fall back to #defined DEFAULT_OPERATING_FREQUENCY
  *
  * @param[in] radio         Radio unit ID.
  *
@@ -719,13 +721,15 @@ int pktDisplayFrequencyCode(const radio_freq_t code, char *buf, size_t size) {
  * @api
  */
 radio_freq_t pktGetDefaultOperatingFrequency(const radio_unit_t radio) {
-  /* FIXME: Default frequency in config to be per radio. */
-  (void)radio;
-  /* FIXME: INVALID relies on 0 in conf if no default set. */
-  if(conf_sram.freq != FREQ_RADIO_INVALID)
+  radio_band_t *band = pktCheckAllowedFrequency(radio, conf_sram.freq);
+  if(band != NULL)
     return conf_sram.freq;
-  else
-    return DEFAULT_OPERATING_FREQ;
+  radio_config_t *radio_data = pktGetRadioData(radio);
+  if(pktCheckAllowedFrequency(radio, radio_data->def_aprs))
+    /* Use default APRS frequency in radio configuration. */
+    return radio_data->def_aprs;
+  /* Fall back to defined default as last resort. */
+  return DEFAULT_OPERATING_FREQ;
 }
 
 /**
@@ -733,9 +737,9 @@ radio_freq_t pktGetDefaultOperatingFrequency(const radio_unit_t radio) {
  *
  * @param[in] radio         Radio unit ID.
  *
- * @return    Actual operating frequency or special code
- * @retval    Operating receive frequency or code if receive is active
- * @retval    Default frequency otherwise.
+ * @return    Actual operating frequency or special code.
+ * @retval    Absolute receive frequency or code if receive is active.
+ * @retval    Default operating frequency if receive not active.
  *
  * @notapi
  */
@@ -768,20 +772,16 @@ radio_freq_t pktGetReceiveOperatingFrequency(const radio_unit_t radio) {
  * @retval    FREQ_RADIO_INVALID if frequency or radio ID is invalid
  *
  * @api
- *
- * TODO: Return pointer to band or NULL if invalid.
  */
 radio_band_t *pktCheckAllowedFrequency(const radio_unit_t radio,
-                                      radio_freq_t freq) {
+                                      const radio_freq_t freq) {
   /* Check validity. */
   uint8_t radios = pktGetNumRadios();
   const radio_config_t *list = pktGetRadioList();
   for(uint8_t i = 0; i < radios; i++) {
-    if(list->unit == radio) {
-      for(uint8_t x = 0; x < NUM_BANDS_PER_RADIO; x++) {
-        if(list->bands[x] == NULL)
-          /* Vacant band slot in this radio. */
-            continue;
+    if(list->unit == radio && list->bands != NULL) {
+      uint8_t x = 0;
+      while(list->bands[x] != NULL) {
         if(list->bands[x]->start <= freq
             && freq < list->bands[x]->end)
           return list->bands[x];
@@ -866,7 +866,7 @@ radio_freq_t pktComputeOperatingFrequency(const radio_unit_t radio,
 }
 
 /**
- *
+ * HAL functions
  */
 bool pktLLDradioInit(const radio_unit_t radio) {
   /* TODO: Implement hardware mapping. */
@@ -933,9 +933,9 @@ bool pktLLDradioSendPacket(radio_task_object_t *rto) {
 
 /**
  * @brief   Enable reception.
- * @notes   This is the API interface to the radio LLD.
+ * @notes   This is the HAL API to the radio LLD.
  * @notes   Currently just map directly to 446x driver.
- * @notes   In future would implement a lookup and VMT to access radio methods.
+ * @notes   In future a VMT lookup would access the relevant radio methods.
  *
  * @param[in] radio radio unit ID.
  * @param[in] rto   pointer to radio task object
@@ -950,8 +950,6 @@ bool pktLLDradioEnableReceive(const radio_unit_t radio,
                          radio_task_object_t *rto) {
   packet_svc_t *handler = pktGetServiceObject(radio);
 
-  //chDbgAssert(handler != NULL, "invalid radio ID");
-
   if(handler == NULL)
     return false;
 
@@ -1131,4 +1129,5 @@ uint8_t pktLLDradioReadCCA(const radio_unit_t radio) {
    */
   return Si446x_readCCA(radio);
 }
+
 /** @} */
diff --git a/tracker/software/source/pkt/managers/pktradio.h b/tracker/software/source/pkt/managers/pktradio.h
index 2dd70d39..b76174a5 100644
--- a/tracker/software/source/pkt/managers/pktradio.h
+++ b/tracker/software/source/pkt/managers/pktradio.h
@@ -139,12 +139,12 @@ extern "C" {
   void      		pktScheduleThreadRelease(const radio_unit_t radio,
                                 thread_t *thread);
   msg_t     		pktAcquireRadio(const radio_unit_t radio,
-            		                sysinterval_t timeout);
+            		                const sysinterval_t timeout);
   void      		pktReleaseRadio(const radio_unit_t radio);
   const radio_config_t *pktGetRadioList(void);
   uint8_t           pktGetNumRadios(void);
   radio_band_t 		*pktCheckAllowedFrequency(const radio_unit_t radio,
-                                        radio_freq_t freq);
+                                        const radio_freq_t freq);
   radio_freq_t 		pktComputeOperatingFrequency(const radio_unit_t radio,
                                             radio_freq_t base_freq,
                                             channel_hz_t step,
diff --git a/tracker/software/source/pkt/pktconf.h b/tracker/software/source/pkt/pktconf.h
index f0f3fccd..249d5fa5 100644
--- a/tracker/software/source/pkt/pktconf.h
+++ b/tracker/software/source/pkt/pktconf.h
@@ -174,10 +174,8 @@ typedef uint32_t            statusmask_t;    /**< Mask of status identifiers. */
 #include "ax25_dump.h"
 #include "si446x.h"
 #include "pktevt.h"
-
-#ifndef PKT_IS_TEST_PROJECT
 #include "debug.h"
-#endif
+
 extern packet_svc_t RPKTD1;
 
 /*===========================================================================*/
diff --git a/tracker/software/source/pkt/pkttypes.h b/tracker/software/source/pkt/pkttypes.h
index 3cc3970d..d14face9 100644
--- a/tracker/software/source/pkt/pkttypes.h
+++ b/tracker/software/source/pkt/pkttypes.h
@@ -97,9 +97,18 @@ typedef struct radioBand {
   radio_freq_t  start;
   radio_freq_t  end;
   channel_hz_t  step;
-  radio_freq_t  def_aprs;
+  //radio_freq_t  def_aprs;
 } radio_band_t;
 
+typedef struct radioConfig {
+  radio_unit_t  unit;
+  radio_type_t  type;
+  void          *cfg;
+  void          *dat;
+  radio_freq_t  def_aprs;       /**< A frequency in one of the bands. */
+  radio_band_t  **bands;
+} radio_config_t;
+
 typedef uint8_t ax25char_t;
 
 typedef int32_t gps_coord_t;