diff --git a/firmware/common/hackrf_core.c b/firmware/common/hackrf_core.c
index 6b792a2f..50e2b7ae 100644
--- a/firmware/common/hackrf_core.c
+++ b/firmware/common/hackrf_core.c
@@ -600,6 +600,7 @@ void cpu_clock_init(void)
 	CGU_BASE_SSP1_CLK = CGU_BASE_SSP1_CLK_AUTOBLOCK(1)
 			| CGU_BASE_SSP1_CLK_CLK_SEL(CGU_SRC_PLL1);
 
+#if (defined JAWBREAKER || defined HACKRF_ONE)
 	/* Disable unused clocks */
 	/* Start with PLLs */
 	CGU_PLL0AUDIO_CTRL = CGU_PLL0AUDIO_CTRL_PD(1);
@@ -665,6 +666,13 @@ void cpu_clock_init(void)
 	// CCU2_CLK_APB2_USART3_CFG = 0;
 	// CCU2_CLK_APLL_CFG = 0;
 	// CCU2_CLK_SDIO_CFG = 0;
+#endif
+
+#ifdef RAD1O
+	/* Disable unused clock outputs. They generate noise. */
+	scu_pinmux(CLK0, SCU_CLK_IN | SCU_CONF_FUNCTION7);
+	scu_pinmux(CLK2, SCU_CLK_IN | SCU_CONF_FUNCTION7);
+#endif
 }
 
 
diff --git a/host/hackrf-tools/src/hackrf_sweep.c b/host/hackrf-tools/src/hackrf_sweep.c
index 6a9d0f19..3d400942 100644
--- a/host/hackrf-tools/src/hackrf_sweep.c
+++ b/host/hackrf-tools/src/hackrf_sweep.c
@@ -98,13 +98,14 @@ int gettimeofday(struct timeval *tv, void* ignored) {
 #define TUNE_STEP (DEFAULT_SAMPLE_RATE_HZ / FREQ_ONE_MHZ)
 #define OFFSET 7500000
 
-#define DEFAULT_SAMPLE_COUNT 0x2000
 #define BLOCKS_PER_TRANSFER 16
+#define THROWAWAY_BLOCKS 2
 
 #if defined _WIN32
 	#define sleep(a) Sleep( (a*1000) )
 #endif
 
+uint32_t num_samples = SAMPLES_PER_BLOCK;
 int num_ranges = 0;
 uint16_t frequencies[MAX_SWEEP_RANGES*2];
 
@@ -202,11 +203,13 @@ int rx_callback(hackrf_transfer* transfer) {
 	int i, j;
 	struct tm *fft_time;
 	char time_str[50];
+	struct timeval usb_transfer_time;
 
 	if(NULL == fd) {
 		return -1;
 	}
 
+	gettimeofday(&usb_transfer_time, NULL);
 	byte_count += transfer->valid_length;
 	buf = (int8_t*) transfer->buffer;
 	for(j=0; j<BLOCKS_PER_TRANSFER; j++) {
@@ -224,7 +227,14 @@ int rx_callback(hackrf_transfer* transfer) {
 				do_exit = true;
 			}
 			sweep_started = true;
-			gettimeofday(&time_stamp, NULL);
+			time_stamp = usb_transfer_time;
+			time_stamp.tv_usec +=
+					(uint64_t)(num_samples + THROWAWAY_BLOCKS * SAMPLES_PER_BLOCK)
+					* j * FREQ_ONE_MHZ / DEFAULT_SAMPLE_RATE_HZ;
+			if(999999 < time_stamp.tv_usec) {
+				time_stamp.tv_usec = time_stamp.tv_usec % 1000000;
+				time_stamp.tv_sec += time_stamp.tv_usec / 1000000;
+			}
 		}
 		if(do_exit) {
 			return 0;
@@ -270,7 +280,7 @@ int rx_callback(hackrf_transfer* transfer) {
 			strftime(time_str, 50, "%Y-%m-%d, %H:%M:%S", fft_time);
 			fprintf(fd, "%s.%06ld, %" PRIu64 ", %" PRIu64 ", %.2f, %u",
 					time_str,
-					time_stamp.tv_usec,
+					(long int)time_stamp.tv_usec,
 					(uint64_t)(frequency),
 					(uint64_t)(frequency+DEFAULT_SAMPLE_RATE_HZ/4),
 					fft_bin_width,
@@ -281,7 +291,7 @@ int rx_callback(hackrf_transfer* transfer) {
 			fprintf(fd, "\n");
 			fprintf(fd, "%s.%06ld, %" PRIu64 ", %" PRIu64 ", %.2f, %u",
 					time_str,
-					time_stamp.tv_usec,
+					(long int)time_stamp.tv_usec,
 					(uint64_t)(frequency+(DEFAULT_SAMPLE_RATE_HZ/2)),
 					(uint64_t)(frequency+((DEFAULT_SAMPLE_RATE_HZ*3)/4)),
 					fft_bin_width,
@@ -341,7 +351,6 @@ int main(int argc, char** argv) {
 	struct timeval t_end;
 	float time_diff;
 	unsigned int lna_gain=16, vga_gain=20;
-	uint32_t num_samples = DEFAULT_SAMPLE_COUNT;
 	int step_count;
 	uint32_t freq_min = 0;
 	uint32_t freq_max = 6000;