diff --git a/src/ubx.cpp b/src/ubx.cpp
index 8bbd26b..129f6b4 100644
--- a/src/ubx.cpp
+++ b/src/ubx.cpp
@@ -93,6 +93,7 @@ GPSDriverUBX::configure(unsigned &baudrate, OutputMode output_mode, GNSSSystemsM
 {
 	_configured = false;
 	_output_mode = output_mode;
+	_gnssSystems = gnssSystems;
 
 	ubx_payload_tx_cfg_prt_t cfg_prt[2];
 
@@ -380,6 +381,80 @@ int GPSDriverUBX::configureDevicePreV27()
 		return -1;
 	}
 
+	/* configure active GNSS systems (number of channels and used signals taken from U-Center default) */
+	if (static_cast<int32_t>(_gnssSystems) != 0) {
+		memset(&_buf.payload_tx_cfg_gnss, 0, sizeof(_buf.payload_tx_cfg_gnss));
+		_buf.payload_tx_cfg_gnss.msgVer = 0x00;
+		_buf.payload_tx_cfg_gnss.numTrkChHw = 0x00;  // read only
+		_buf.payload_tx_cfg_gnss.numTrkChUse = 0xFF;  // use max number of HW channels
+		_buf.payload_tx_cfg_gnss.numConfigBlocks = 7;  // always configure all systems
+
+		// GPS and QZSS should always be enabled and disabled together, according to uBlox
+		_buf.payload_tx_cfg_gnss.block[0].gnssId = UBX_TX_CFG_GNSS_GNSSID_GPS;
+		_buf.payload_tx_cfg_gnss.block[1].gnssId = UBX_TX_CFG_GNSS_GNSSID_QZSS;
+
+		if (_gnssSystems & GNSSSystemsMask::ENABLE_GPS) {
+			UBX_DEBUG("GNSS Systems: Use GPS + QZSS");
+			_buf.payload_tx_cfg_gnss.block[0].resTrkCh = 8;
+			_buf.payload_tx_cfg_gnss.block[0].maxTrkCh = 16;
+			_buf.payload_tx_cfg_gnss.block[0].flags = UBX_TX_CFG_GNSS_FLAGS_GPS_L1CA | UBX_TX_CFG_GNSS_FLAGS_ENABLE;
+			_buf.payload_tx_cfg_gnss.block[1].resTrkCh = 0;
+			_buf.payload_tx_cfg_gnss.block[1].maxTrkCh = 3;
+			_buf.payload_tx_cfg_gnss.block[1].flags = UBX_TX_CFG_GNSS_FLAGS_QZSS_L1CA | UBX_TX_CFG_GNSS_FLAGS_ENABLE;
+		}
+
+		_buf.payload_tx_cfg_gnss.block[2].gnssId = UBX_TX_CFG_GNSS_GNSSID_SBAS;
+
+		if (_gnssSystems & GNSSSystemsMask::ENABLE_SBAS) {
+			UBX_DEBUG("GNSS Systems: Use SBAS");
+			_buf.payload_tx_cfg_gnss.block[2].resTrkCh = 1;
+			_buf.payload_tx_cfg_gnss.block[2].maxTrkCh = 3;
+			_buf.payload_tx_cfg_gnss.block[2].flags = UBX_TX_CFG_GNSS_FLAGS_SBAS_L1CA | UBX_TX_CFG_GNSS_FLAGS_ENABLE;
+		}
+
+		_buf.payload_tx_cfg_gnss.block[3].gnssId = UBX_TX_CFG_GNSS_GNSSID_GALILEO;
+
+		if (_gnssSystems & GNSSSystemsMask::ENABLE_GALILEO) {
+			UBX_DEBUG("GNSS Systems: Use Galileo");
+			_buf.payload_tx_cfg_gnss.block[3].resTrkCh = 4;
+			_buf.payload_tx_cfg_gnss.block[3].maxTrkCh = 8;
+			_buf.payload_tx_cfg_gnss.block[3].flags = UBX_TX_CFG_GNSS_FLAGS_GALILEO_E1 | UBX_TX_CFG_GNSS_FLAGS_ENABLE;
+		}
+
+		_buf.payload_tx_cfg_gnss.block[4].gnssId = UBX_TX_CFG_GNSS_GNSSID_BEIDOU;
+
+		if (_gnssSystems & GNSSSystemsMask::ENABLE_BEIDOU) {
+			UBX_DEBUG("GNSS Systems: Use BeiDou");
+			_buf.payload_tx_cfg_gnss.block[4].resTrkCh = 8;
+			_buf.payload_tx_cfg_gnss.block[4].maxTrkCh = 16;
+			_buf.payload_tx_cfg_gnss.block[4].flags = UBX_TX_CFG_GNSS_FLAGS_BEIDOU_B1I | UBX_TX_CFG_GNSS_FLAGS_ENABLE;
+		}
+
+		_buf.payload_tx_cfg_gnss.block[5].gnssId = UBX_TX_CFG_GNSS_GNSSID_GLONASS;
+
+		if (_gnssSystems & GNSSSystemsMask::ENABLE_GLONASS) {
+			UBX_DEBUG("GNSS Systems: Use GLONASS");
+			_buf.payload_tx_cfg_gnss.block[5].resTrkCh = 8;
+			_buf.payload_tx_cfg_gnss.block[5].maxTrkCh = 14;
+			_buf.payload_tx_cfg_gnss.block[5].flags = UBX_TX_CFG_GNSS_FLAGS_GLONASS_L1 | UBX_TX_CFG_GNSS_FLAGS_ENABLE;
+		}
+
+		// IMES always disabled
+		_buf.payload_tx_cfg_gnss.block[6].gnssId = UBX_TX_CFG_GNSS_GNSSID_IMES;
+		_buf.payload_tx_cfg_gnss.block[6].flags = 0;
+
+		// send message
+		if (!sendMessage(UBX_MSG_CFG_GNSS, (uint8_t *)&_buf, sizeof(_buf.payload_tx_cfg_gnss))) {
+			GPS_ERR("UBX CFG-GNSS message send failed");
+			return -1;
+		}
+
+		if (waitForAck(UBX_MSG_CFG_GNSS, UBX_CONFIG_TIMEOUT, true) < 0) {
+			GPS_ERR("UBX CFG-GNSS message ACK failed");
+			return -1;
+		}
+	}
+
 	/* configure message rates */
 	/* the last argument is divisor for measurement rate (set by CFG RATE), i.e. 1 means 5Hz */
 
@@ -472,6 +547,80 @@ int GPSDriverUBX::configureDevice()
 
 	waitForAck(UBX_MSG_CFG_VALSET, UBX_CONFIG_TIMEOUT, false);
 
+	// configure active GNSS systems (number of channels and used signals taken from U-Center default)
+	if (static_cast<int32_t>(_gnssSystems) != 0) {
+		memset(&_buf.payload_tx_cfg_gnss, 0, sizeof(_buf.payload_tx_cfg_gnss));
+		_buf.payload_tx_cfg_gnss.msgVer = 0x00;
+		_buf.payload_tx_cfg_gnss.numTrkChHw = 0x00;  // read only
+		_buf.payload_tx_cfg_gnss.numTrkChUse = 0xFF;  // use max number of HW channels
+		_buf.payload_tx_cfg_gnss.numConfigBlocks = 7;  // always configure all systems
+
+		// GPS and QZSS should always be enabled and disabled together, according to uBlox
+		_buf.payload_tx_cfg_gnss.block[0].gnssId = UBX_TX_CFG_GNSS_GNSSID_GPS;
+		_buf.payload_tx_cfg_gnss.block[1].gnssId = UBX_TX_CFG_GNSS_GNSSID_QZSS;
+
+		if (_gnssSystems & GNSSSystemsMask::ENABLE_GPS) {
+			UBX_DEBUG("GNSS Systems: Use GPS + QZSS");
+			_buf.payload_tx_cfg_gnss.block[0].resTrkCh = 8;
+			_buf.payload_tx_cfg_gnss.block[0].maxTrkCh = 16;
+			_buf.payload_tx_cfg_gnss.block[0].flags = UBX_TX_CFG_GNSS_FLAGS_GPS_L1CA | UBX_TX_CFG_GNSS_FLAGS_ENABLE;
+			_buf.payload_tx_cfg_gnss.block[1].resTrkCh = 0;
+			_buf.payload_tx_cfg_gnss.block[1].maxTrkCh = 3;
+			_buf.payload_tx_cfg_gnss.block[1].flags = UBX_TX_CFG_GNSS_FLAGS_QZSS_L1CA | UBX_TX_CFG_GNSS_FLAGS_ENABLE;
+		}
+
+		_buf.payload_tx_cfg_gnss.block[2].gnssId = UBX_TX_CFG_GNSS_GNSSID_SBAS;
+
+		if (_gnssSystems & GNSSSystemsMask::ENABLE_SBAS) {
+			UBX_DEBUG("GNSS Systems: Use SBAS");
+			_buf.payload_tx_cfg_gnss.block[2].resTrkCh = 1;
+			_buf.payload_tx_cfg_gnss.block[2].maxTrkCh = 3;
+			_buf.payload_tx_cfg_gnss.block[2].flags = UBX_TX_CFG_GNSS_FLAGS_SBAS_L1CA | UBX_TX_CFG_GNSS_FLAGS_ENABLE;
+		}
+
+		_buf.payload_tx_cfg_gnss.block[3].gnssId = UBX_TX_CFG_GNSS_GNSSID_GALILEO;
+
+		if (_gnssSystems & GNSSSystemsMask::ENABLE_GALILEO) {
+			UBX_DEBUG("GNSS Systems: Use Galileo");
+			_buf.payload_tx_cfg_gnss.block[3].resTrkCh = 4;
+			_buf.payload_tx_cfg_gnss.block[3].maxTrkCh = 8;
+			_buf.payload_tx_cfg_gnss.block[3].flags = UBX_TX_CFG_GNSS_FLAGS_GALILEO_E1 | UBX_TX_CFG_GNSS_FLAGS_ENABLE;
+		}
+
+		_buf.payload_tx_cfg_gnss.block[4].gnssId = UBX_TX_CFG_GNSS_GNSSID_BEIDOU;
+
+		if (_gnssSystems & GNSSSystemsMask::ENABLE_BEIDOU) {
+			UBX_DEBUG("GNSS Systems: Use BeiDou");
+			_buf.payload_tx_cfg_gnss.block[4].resTrkCh = 8;
+			_buf.payload_tx_cfg_gnss.block[4].maxTrkCh = 16;
+			_buf.payload_tx_cfg_gnss.block[4].flags = UBX_TX_CFG_GNSS_FLAGS_BEIDOU_B1I | UBX_TX_CFG_GNSS_FLAGS_ENABLE;
+		}
+
+		_buf.payload_tx_cfg_gnss.block[5].gnssId = UBX_TX_CFG_GNSS_GNSSID_GLONASS;
+
+		if (_gnssSystems & GNSSSystemsMask::ENABLE_GLONASS) {
+			UBX_DEBUG("GNSS Systems: Use GLONASS");
+			_buf.payload_tx_cfg_gnss.block[5].resTrkCh = 8;
+			_buf.payload_tx_cfg_gnss.block[5].maxTrkCh = 14;
+			_buf.payload_tx_cfg_gnss.block[5].flags = UBX_TX_CFG_GNSS_FLAGS_GLONASS_L1 | UBX_TX_CFG_GNSS_FLAGS_ENABLE;
+		}
+
+		// IMES always disabled
+		_buf.payload_tx_cfg_gnss.block[6].gnssId = UBX_TX_CFG_GNSS_GNSSID_IMES;
+		_buf.payload_tx_cfg_gnss.block[6].flags = 0;
+
+		// send message
+		if (!sendMessage(UBX_MSG_CFG_GNSS, (uint8_t *)&_buf, sizeof(_buf.payload_tx_cfg_gnss))) {
+			GPS_ERR("UBX CFG-GNSS message send failed");
+			return -1;
+		}
+
+		if (waitForAck(UBX_MSG_CFG_GNSS, UBX_CONFIG_TIMEOUT, true) < 0) {
+			GPS_ERR("UBX CFG-GNSS message ACK failed");
+			return -1;
+		}
+	}
+
 	// Configure message rates
 	// Send a new CFG-VALSET message to make sure it does not get too large
 	cfg_valset_msg_size = initCfgValset();
diff --git a/src/ubx.h b/src/ubx.h
index 160ea0f..74120cc 100644
--- a/src/ubx.h
+++ b/src/ubx.h
@@ -101,6 +101,7 @@
 #define UBX_ID_CFG_RST        0x04
 #define UBX_ID_CFG_SBAS       0x16
 #define UBX_ID_CFG_TMODE3     0x71 // deprecated in protocol version >= 27 -> use CFG_VALSET
+#define UBX_ID_CFG_GNSS       0x3E
 #define UBX_ID_CFG_VALSET     0x8A
 #define UBX_ID_CFG_VALGET     0x8B
 #define UBX_ID_CFG_VALDEL     0x8C
@@ -151,6 +152,7 @@
 #define UBX_MSG_CFG_RST       ((UBX_CLASS_CFG) | UBX_ID_CFG_RST << 8)
 #define UBX_MSG_CFG_SBAS      ((UBX_CLASS_CFG) | UBX_ID_CFG_SBAS << 8)
 #define UBX_MSG_CFG_TMODE3    ((UBX_CLASS_CFG) | UBX_ID_CFG_TMODE3 << 8)
+#define UBX_MSG_CFG_GNSS      ((UBX_CLASS_CFG) | UBX_ID_CFG_GNSS << 8)
 #define UBX_MSG_CFG_VALGET    ((UBX_CLASS_CFG) | UBX_ID_CFG_VALGET << 8)
 #define UBX_MSG_CFG_VALSET    ((UBX_CLASS_CFG) | UBX_ID_CFG_VALSET << 8)
 #define UBX_MSG_CFG_VALDEL    ((UBX_CLASS_CFG) | UBX_ID_CFG_VALDEL << 8)
@@ -226,6 +228,34 @@
 #define UBX_TX_CFG_RST_MODE_HARDWARE            0
 #define UBX_TX_CFG_RST_MODE_SOFTWARE            1
 
+/* TX CFG-GNSS message contents
+ */
+#define UBX_TX_CFG_GNSS_GNSSID_GPS              0       /**< gnssId of GPS */
+#define UBX_TX_CFG_GNSS_GNSSID_SBAS             1       /**< gnssId of SBAS */
+#define UBX_TX_CFG_GNSS_GNSSID_GALILEO          2       /**< gnssId of Galileo */
+#define UBX_TX_CFG_GNSS_GNSSID_BEIDOU           3       /**< gnssId of BeiDou */
+#define UBX_TX_CFG_GNSS_GNSSID_IMES             4       /**< gnssId of IMES */
+#define UBX_TX_CFG_GNSS_GNSSID_QZSS             5       /**< gnssId of QZSS */
+#define UBX_TX_CFG_GNSS_GNSSID_GLONASS          6       /**< gnssId of GLONASS */
+#define UBX_TX_CFG_GNSS_FLAGS_ENABLE            0x00000001  /**< Enable this GNSS system */
+#define UBX_TX_CFG_GNSS_FLAGS_GPS_L1CA          0x00010000  /**< GPS: Use L1C/A Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_GPS_L2C           0x00100000  /**< GPS: Use L2C Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_GPS_L5            0x00200000  /**< GPS: Use L5 Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_SBAS_L1CA         0x00010000  /**< SBAS: Use L1C/A Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_GALILEO_E1        0x00010000  /**< Galileo: Use E1 Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_GALILEO_E5A       0x00100000  /**< Galileo: Use E5a Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_GALILEO_E5B       0x00200000  /**< Galileo: Use E5b Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_BEIDOU_B1I        0x00010000  /**< BeiDou: Use B1I Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_BEIDOU_B2I        0x00100000  /**< BeiDou: Use B2I Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_BEIDOU_B2A        0x00800000  /**< BeiDou: Use B2A Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_IMES_L1           0x00010000  /**< IMES: Use L1 Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_QZSS_L1CA         0x00010000  /**< QZSS: Use L1C/A Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_QZSS_L1S          0x00040000  /**< QZSS: Use L1S Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_QZSS_L2C          0x00100000  /**< QZSS: Use L2C Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_QZSS_L5           0x00200000  /**< QZSS: Use L5 Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_GLONASS_L1        0x00010000  /**< GLONASS: Use L1 Signal */
+#define UBX_TX_CFG_GNSS_FLAGS_GLONASS_L2        0x00100000  /**< GLONASS: Use L2 Signal */
+
 /* Key ID's for CFG-VAL{GET,SET,DEL} */
 #define UBX_CFG_KEY_CFG_UART1_BAUDRATE          0x40520001
 #define UBX_CFG_KEY_CFG_UART1_STOPBITS          0x20520002
@@ -718,6 +748,23 @@ typedef struct {
 	uint8_t  reserved3[8];
 } ubx_payload_tx_cfg_tmode3_t;
 
+typedef struct {
+	uint8_t msgVer;           /**< Message version (expected 0x00) */
+	uint8_t numTrkChHw;       /**< Number of tracking channels available (read only) */
+	uint8_t numTrkChUse;      /**< Number of tracking channels to use (0xFF for numTrkChHw) */
+	uint8_t numConfigBlocks;  /**< Count of repeated blocks */
+
+	struct ubx_payload_tx_cgf_gnss_block_t {
+		uint8_t gnssId;     /**< GNSS ID */
+		uint8_t resTrkCh;   /**< Number of reseved (minimum) tracking channels */
+		uint8_t maxTrkCh;   /**< Maximum number or tracking channels */
+		uint8_t reserved1;
+		uint32_t flags;     /**< Bitfield flags (see UBX_TX_CFG_GNSS_FLAGS_*) */
+	};
+
+	ubx_payload_tx_cgf_gnss_block_t block[7];  /**< GPS, SBAS, Galileo, BeiDou, IMES 0-8, QZSS, GLONASS */
+} ubx_payload_tx_cfg_gnss_t;
+
 /* NAV RELPOSNED (protocol version 27+) */
 typedef struct {
 	uint8_t     version;         /**< message version (expected 0x01) */
@@ -772,6 +819,7 @@ typedef union {
 	ubx_payload_tx_cfg_tmode3_t       payload_tx_cfg_tmode3;
 	ubx_payload_tx_cfg_cfg_t          payload_tx_cfg_cfg;
 	ubx_payload_tx_cfg_valset_t       payload_tx_cfg_valset;
+	ubx_payload_tx_cfg_gnss_t         payload_tx_cfg_gnss;
 	ubx_payload_rx_nav_relposned_t    payload_rx_nav_relposned;
 } ubx_buf_t;
 
@@ -1001,6 +1049,8 @@ class GPSDriverUBX : public GPSBaseStationSupport
 
 	OutputMode _output_mode{OutputMode::GPS};
 
+	GNSSSystemsMask _gnssSystems{};
+
 	RTCMParsing *_rtcm_parsing{nullptr};
 
 	const UBXMode _mode;