diff --git a/gnss-converters.cabal b/gnss-converters.cabal
--- a/gnss-converters.cabal
+++ b/gnss-converters.cabal
@@ -1,5 +1,5 @@
 name: gnss-converters
-version: 0.3.6
+version: 0.3.7
 cabal-version: >=1.22
 build-type: Simple
 license: BSD3
@@ -26,6 +26,7 @@
     build-depends:
         base >=4.8 && <5,
         basic-prelude >=0.5.2,
+        conduit >=1.2.10,
         exceptions >=0.8.3,
         extra >=1.4.10,
         lens >=4.13,
@@ -35,7 +36,8 @@
         rtcm >=0.2.2,
         sbp >=2.2.11,
         time >=1.5.0.1,
-        transformers-base >=0.4.4
+        transformers-base >=0.4.4,
+        vector >=0.11.0.0
     default-language: Haskell2010
     hs-source-dirs: src
     ghc-options: -Wall
diff --git a/main/RTCM32SBP.hs b/main/RTCM32SBP.hs
--- a/main/RTCM32SBP.hs
+++ b/main/RTCM32SBP.hs
@@ -10,22 +10,21 @@
 --
 -- RTCM3 to SBP tool.
 
-import           BasicPrelude
-import           Control.Monad.Trans.Resource
-import           Data.Conduit
-import           Data.Conduit.Binary
-import qualified Data.Conduit.List                 as CL
-import           Data.Conduit.Serialization.Binary
-import           Data.RTCM3.SBP
-import           Data.RTCM3.SBP.Types
-import           System.IO
+import BasicPrelude
+import Control.Monad.Trans.Resource
+import Data.Conduit
+import Data.Conduit.Binary
+import Data.Conduit.Serialization.Binary
+import Data.RTCM3.SBP
+import Data.RTCM3.SBP.Types
+import System.IO
 
 main :: IO ()
 main = do
   s <- newStore
   runResourceT $ runConvertT s $
-    sourceHandle stdin    =$=
-    conduitDecode         =$=
-    CL.concatMapM convert =$=
-    conduitEncode         $$
+    sourceHandle stdin =$=
+    conduitDecode      =$=
+    converter          =$=
+    conduitEncode      $$
     sinkHandle stdout
diff --git a/src/Data/RTCM3/SBP.hs b/src/Data/RTCM3/SBP.hs
--- a/src/Data/RTCM3/SBP.hs
+++ b/src/Data/RTCM3/SBP.hs
@@ -14,22 +14,23 @@
 module Data.RTCM3.SBP
   ( toWn
   , mjdEpoch
-  , convert
+  , converter
   , newStore
   , validateIodcIode
   , gpsUriToUra
   ) where
 
-import BasicPrelude
-import Control.Lens
-import Data.Bits
-import Data.IORef
-import Data.RTCM3
-import Data.RTCM3.SBP.Observations
-import Data.RTCM3.SBP.Types
-import Data.Time
-import Data.Word
-import SwiftNav.SBP
+import           BasicPrelude
+import           Control.Lens
+import           Data.Bits
+import           Data.Conduit
+import           Data.IORef
+import           Data.RTCM3
+import qualified Data.RTCM3.SBP.Observations as Observations
+import           Data.RTCM3.SBP.Time
+import           Data.RTCM3.SBP.Types
+import           Data.Word
+import           SwiftNav.SBP
 
 {-# ANN module ("HLint: ignore Redundant if"::String) #-}
 
@@ -44,8 +45,8 @@
 --------------------------------------------------------------------------------
 -- General utilities
 
-applyScaleFactor :: (Floating a, Integral b) => a -> a -> b -> a
-applyScaleFactor n p x = (n ** p)  * fromIntegral x
+applyScaleFactor :: (Floating a, Integral b) => a -> b -> a
+applyScaleFactor p x = (2 ** p)  * fromIntegral x
 
 --------------------------------------------------------------------------------
 -- GNSS RTCM observation reconstruction utilities
@@ -165,54 +166,60 @@
   toc           <- toGpsTimeSec (m ^. msg1019_ephemeris ^. gpsEphemeris_wn) (m ^. msg1019_ephemeris ^. gpsEphemeris_toc)
   return MsgEphemerisGps
     { _msgEphemerisGps_common   = commonContent
-    , _msgEphemerisGps_tgd      =         applyScaleFactor 2 (-31) $ m ^. msg1019_ephemeris ^. gpsEphemeris_tgd
-    , _msgEphemerisGps_c_rs     =         applyScaleFactor 2 (-5)  $ m ^. msg1019_ephemeris ^. gpsEphemeris_c_rs
-    , _msgEphemerisGps_c_rc     =         applyScaleFactor 2 (-5)  $ m ^. msg1019_ephemeris ^. gpsEphemeris_c_rc
-    , _msgEphemerisGps_c_uc     =         applyScaleFactor 2 (-29) $ m ^. msg1019_ephemeris ^. gpsEphemeris_c_uc
-    , _msgEphemerisGps_c_us     =         applyScaleFactor 2 (-29) $ m ^. msg1019_ephemeris ^. gpsEphemeris_c_us
-    , _msgEphemerisGps_c_ic     =         applyScaleFactor 2 (-29) $ m ^. msg1019_ephemeris ^. gpsEphemeris_c_ic
-    , _msgEphemerisGps_c_is     =         applyScaleFactor 2 (-29) $ m ^. msg1019_ephemeris ^. gpsEphemeris_c_is
-    , _msgEphemerisGps_dn       = gpsPi * applyScaleFactor 2 (-43)  (m ^. msg1019_ephemeris ^. gpsEphemeris_dn)
-    , _msgEphemerisGps_m0       = gpsPi * applyScaleFactor 2 (-31)  (m ^. msg1019_ephemeris ^. gpsEphemeris_m0)
-    , _msgEphemerisGps_ecc      =         applyScaleFactor 2 (-33) $ m ^. msg1019_ephemeris ^. gpsEphemeris_ecc
-    , _msgEphemerisGps_sqrta    =         applyScaleFactor 2 (-19) $ m ^. msg1019_ephemeris ^. gpsEphemeris_sqrta
-    , _msgEphemerisGps_omega0   = gpsPi * applyScaleFactor 2 (-31)  (m ^. msg1019_ephemeris ^. gpsEphemeris_omega0)
-    , _msgEphemerisGps_omegadot = gpsPi * applyScaleFactor 2 (-43)  (m ^. msg1019_ephemeris ^. gpsEphemeris_omegadot)
-    , _msgEphemerisGps_w        = gpsPi * applyScaleFactor 2 (-31)  (m ^. msg1019_ephemeris ^. gpsEphemeris_w)
-    , _msgEphemerisGps_inc      = gpsPi * applyScaleFactor 2 (-31)  (m ^. msg1019_ephemeris ^. gpsEphemeris_i0)
-    , _msgEphemerisGps_inc_dot  = gpsPi * applyScaleFactor 2 (-43)  (m ^. msg1019_ephemeris ^. gpsEphemeris_idot)
-    , _msgEphemerisGps_af0      =         applyScaleFactor 2 (-31) $ m ^. msg1019_ephemeris ^. gpsEphemeris_af0
-    , _msgEphemerisGps_af1      =         applyScaleFactor 2 (-43) $ m ^. msg1019_ephemeris ^. gpsEphemeris_af1
-    , _msgEphemerisGps_af2      =         applyScaleFactor 2 (-55) $ m ^. msg1019_ephemeris ^. gpsEphemeris_af2
-    , _msgEphemerisGps_iodc     =                                    m ^. msg1019_ephemeris ^. gpsEphemeris_iodc
-    , _msgEphemerisGps_iode     =                                    m ^. msg1019_ephemeris ^. gpsEphemeris_iode
+    , _msgEphemerisGps_tgd      =         applyScaleFactor (-31) $ m ^. msg1019_ephemeris ^. gpsEphemeris_tgd
+    , _msgEphemerisGps_c_rs     =         applyScaleFactor (-5)  $ m ^. msg1019_ephemeris ^. gpsEphemeris_c_rs
+    , _msgEphemerisGps_c_rc     =         applyScaleFactor (-5)  $ m ^. msg1019_ephemeris ^. gpsEphemeris_c_rc
+    , _msgEphemerisGps_c_uc     =         applyScaleFactor (-29) $ m ^. msg1019_ephemeris ^. gpsEphemeris_c_uc
+    , _msgEphemerisGps_c_us     =         applyScaleFactor (-29) $ m ^. msg1019_ephemeris ^. gpsEphemeris_c_us
+    , _msgEphemerisGps_c_ic     =         applyScaleFactor (-29) $ m ^. msg1019_ephemeris ^. gpsEphemeris_c_ic
+    , _msgEphemerisGps_c_is     =         applyScaleFactor (-29) $ m ^. msg1019_ephemeris ^. gpsEphemeris_c_is
+    , _msgEphemerisGps_dn       = gpsPi * applyScaleFactor (-43)  (m ^. msg1019_ephemeris ^. gpsEphemeris_dn)
+    , _msgEphemerisGps_m0       = gpsPi * applyScaleFactor (-31)  (m ^. msg1019_ephemeris ^. gpsEphemeris_m0)
+    , _msgEphemerisGps_ecc      =         applyScaleFactor (-33) $ m ^. msg1019_ephemeris ^. gpsEphemeris_ecc
+    , _msgEphemerisGps_sqrta    =         applyScaleFactor (-19) $ m ^. msg1019_ephemeris ^. gpsEphemeris_sqrta
+    , _msgEphemerisGps_omega0   = gpsPi * applyScaleFactor (-31)  (m ^. msg1019_ephemeris ^. gpsEphemeris_omega0)
+    , _msgEphemerisGps_omegadot = gpsPi * applyScaleFactor (-43)  (m ^. msg1019_ephemeris ^. gpsEphemeris_omegadot)
+    , _msgEphemerisGps_w        = gpsPi * applyScaleFactor (-31)  (m ^. msg1019_ephemeris ^. gpsEphemeris_w)
+    , _msgEphemerisGps_inc      = gpsPi * applyScaleFactor (-31)  (m ^. msg1019_ephemeris ^. gpsEphemeris_i0)
+    , _msgEphemerisGps_inc_dot  = gpsPi * applyScaleFactor (-43)  (m ^. msg1019_ephemeris ^. gpsEphemeris_idot)
+    , _msgEphemerisGps_af0      =         applyScaleFactor (-31) $ m ^. msg1019_ephemeris ^. gpsEphemeris_af0
+    , _msgEphemerisGps_af1      =         applyScaleFactor (-43) $ m ^. msg1019_ephemeris ^. gpsEphemeris_af1
+    , _msgEphemerisGps_af2      =         applyScaleFactor (-55) $ m ^. msg1019_ephemeris ^. gpsEphemeris_af2
+    , _msgEphemerisGps_iodc     =                                  m ^. msg1019_ephemeris ^. gpsEphemeris_iodc
+    , _msgEphemerisGps_iode     =                                  m ^. msg1019_ephemeris ^. gpsEphemeris_iode
     , _msgEphemerisGps_toc      = toc
     }
 
+msg1005Converter :: MonadStore e m => Msg1005 -> Conduit i m [SBPMsg]
+msg1005Converter m = do
+  m' <- fromMsg1005 m
+  yield [SBPMsgBasePosEcef m' $ toSBP m' $ toSender $ m ^. msg1005_reference ^. antennaReference_station]
+
+msg1006Converter :: MonadStore e m => Msg1006 -> Conduit i m [SBPMsg]
+msg1006Converter m = do
+  m' <- fromMsg1006 m
+  yield [SBPMsgBasePosEcef m' $ toSBP m' $ toSender $ m ^. msg1006_reference ^. antennaReference_station]
+
+msg1019Converter :: MonadStore e m => Msg1019 -> Conduit i m [SBPMsg]
+msg1019Converter m = do
+  m' <- fromMsg1019 m
+  yield [SBPMsgEphemerisGps m' $ toSBP m' $ toSender 0]
+
 -- | Convert an RTCM message into possibly multiple SBP messages.
 --
-convert :: MonadStore e m => RTCM3Msg -> m [SBPMsg]
-convert = \case
-  (RTCM3Msg1002 m _rtcm3) -> toSBPMsgObs m
-  (RTCM3Msg1004 m _rtcm3) -> toSBPMsgObs m
-  (RTCM3Msg1005 m _rtcm3) -> do
-    let sender =  m ^. msg1005_reference ^. antennaReference_station
-    m' <- fromMsg1005 m
-    return [SBPMsgBasePosEcef m' $ toSBP m' $ toSender sender]
-  (RTCM3Msg1006 m _rtcm3) -> do
-    let sender = m ^. msg1006_reference ^. antennaReference_station
-    m' <- fromMsg1006 m
-    return [SBPMsgBasePosEcef m' $ toSBP m' $ toSender sender]
-  (RTCM3Msg1010 m _rtcm3) -> toSBPMsgObs m
-  (RTCM3Msg1012 m _rtcm3) -> toSBPMsgObs m
-  (RTCM3Msg1019 m _rtcm3) -> do
-    let sender = 0
-    m' <- fromMsg1019 m
-    return [SBPMsgEphemerisGps m' $ toSBP m' $ toSender sender]
-  _rtcm3Msg -> return mempty
+converter :: MonadStore e m => Conduit RTCM3Msg m [SBPMsg]
+converter =
+  awaitForever $ \case
+    (RTCM3Msg1002 m _rtcm3) -> Observations.converter m
+    (RTCM3Msg1004 m _rtcm3) -> Observations.converter m
+    (RTCM3Msg1010 m _rtcm3) -> Observations.converter m
+    (RTCM3Msg1012 m _rtcm3) -> Observations.converter m
+    (RTCM3Msg1005 m _rtcm3) -> msg1005Converter m
+    (RTCM3Msg1006 m _rtcm3) -> msg1006Converter m
+    (RTCM3Msg1019 m _rtcm3) -> msg1019Converter m
+    _rtcm3Msg -> mempty
 
 newStore :: IO Store
 newStore = do
-  day <- utctDay <$> getCurrentTime
-  let wn = fromIntegral $ div (diffDays day (fromGregorian 1980 1 6)) 7
-  Store <$> newIORef wn <*> newIORef mempty
+  t <- currentGpsTime
+  Store <$> newIORef (t ^. gpsTimeNano_wn) <*> newIORef t <*> newIORef mempty <*> newIORef mempty
diff --git a/src/Data/RTCM3/SBP/Observations.hs b/src/Data/RTCM3/SBP/Observations.hs
--- a/src/Data/RTCM3/SBP/Observations.hs
+++ b/src/Data/RTCM3/SBP/Observations.hs
@@ -11,18 +11,20 @@
 -- RTCMv3 to SBP Observation Conversions.
 
 module Data.RTCM3.SBP.Observations
-  ( toSBPMsgObs
+  ( converter
   ) where
 
-import BasicPrelude
+import BasicPrelude         hiding (null)
 import Control.Lens
 import Data.Bits
+import Data.Conduit
 import Data.Int
 import Data.IORef
-import Data.List.Extra
+import Data.List.Extra      hiding (null)
 import Data.RTCM3
 import Data.RTCM3.SBP.Time
 import Data.RTCM3.SBP.Types
+import Data.Vector          hiding (concatMap, length)
 import Data.Word
 import SwiftNav.SBP
 
@@ -39,10 +41,10 @@
 --
 toGpsTimeNano :: MonadStore e m => Word16 -> (GpsTimeNano -> GpsTimeNano) -> m GpsTimeNano
 toGpsTimeNano station rollover = do
-  gpsTimeMap <- view storeGpsTimeMap
-  modifyIORefM gpsTimeMap $ \gpsTimeMap' -> do
-    t <- rollover <$> maybe currentGpsTime return (gpsTimeMap' ^. at station)
-    return (gpsTimeMap' & at station ?~ t, t)
+  timeMap <- view storeGpsTimeMap
+  modifyIORefM timeMap $ \timeMap' -> do
+    t <- rollover <$> maybe currentGpsTime return (timeMap' ^. at station)
+    return (timeMap' & at station ?~ t, t)
 
 -- | Default observation doppler.
 --
@@ -303,36 +305,41 @@
   gpsTimeNano       :: MonadStore e m => a -> m GpsTimeNano
   packedObsContents :: a -> [PackedObsContent]
   sender            :: a -> Word16
+  synchronous       :: a -> Bool
 
 instance FromObservations Msg1002 where
   gpsTimeNano m     = toGpsTimeNano (m ^. msg1002_header . gpsObservationHeader_station) $ rolloverTowGpsTime (m ^. msg1002_header . gpsObservationHeader_tow)
   packedObsContents = toPackedObsContent . view msg1002_observations
   sender            = toSender . view (msg1002_header . gpsObservationHeader_station)
+  synchronous       = view (msg1002_header . gpsObservationHeader_synchronous)
 
 instance FromObservations Msg1004 where
   gpsTimeNano m     = toGpsTimeNano (m ^. msg1004_header . gpsObservationHeader_station) $ rolloverTowGpsTime (m ^. msg1004_header . gpsObservationHeader_tow)
   packedObsContents = toPackedObsContent . view msg1004_observations
   sender            = toSender . view (msg1004_header . gpsObservationHeader_station)
+  synchronous       = view (msg1004_header . gpsObservationHeader_synchronous)
 
 instance FromObservations Msg1010 where
   gpsTimeNano m     = toGpsTimeNano (m ^. msg1010_header . glonassObservationHeader_station) $ rolloverEpochGpsTime (m ^. msg1010_header . glonassObservationHeader_epoch)
   packedObsContents = toPackedObsContent . view msg1010_observations
   sender            = toSender . view (msg1010_header . glonassObservationHeader_station)
+  synchronous       = view (msg1010_header . glonassObservationHeader_synchronous)
 
 instance FromObservations Msg1012 where
   gpsTimeNano m     = toGpsTimeNano (m ^. msg1012_header . glonassObservationHeader_station) $ rolloverEpochGpsTime (m ^. msg1012_header . glonassObservationHeader_epoch)
   packedObsContents = toPackedObsContent . view msg1012_observations
   sender            = toSender . view (msg1012_header . glonassObservationHeader_station)
+  synchronous       = view (msg1012_header . glonassObservationHeader_synchronous)
 
--- | Convert RTCMv3 observations to SBP observations in chunks.
+-- | Convert RTCMv3 observation(s) to SBP observations in chunks.
 --
-toMsgObs :: (MonadStore e m, FromObservations a) => a -> m [MsgObs]
-toMsgObs m = do
-  let obs = chunksOf maxObs $ packedObsContents m
-  iforM obs $ \i obs' -> do
-    t <- gpsTimeNano m
-    let n = length obs `shiftL` 4 .|. i
-    return $ MsgObs (ObservationHeader t (fromIntegral n)) obs'
+toMsgObs :: Applicative f => GpsTimeNano -> [PackedObsContent] -> Word16 -> f [SBPMsg]
+toMsgObs t obs s = do
+  let chunks = chunksOf maxObs obs
+  ifor chunks $ \i obs' -> do
+    let n = length chunks `shiftL` 4 .|. i
+        m = MsgObs (ObservationHeader t (fromIntegral n)) obs'
+    pure $ SBPMsgObs m $ toSBP m s
   where
     maxObs  = (maxSize - hdrSize) `div` obsSize
     maxSize = 255
@@ -341,8 +348,26 @@
 
 -- | Convert RTCMv3 observation message to SBP observations message(s).
 --
-toSBPMsgObs :: (MonadStore e m, FromObservations a) => a -> m [SBPMsg]
-toSBPMsgObs m = do
-  ms <- toMsgObs m
-  return $ for ms $ \m' ->
-    SBPMsgObs m' $ toSBP m' $ sender m
+converter :: (MonadStore e m, FromObservations a) => a -> Conduit i m [SBPMsg]
+converter m = do
+  time <- view storeGpsTime
+  t    <- liftIO $ readIORef time
+  t'   <- gpsTimeNano m
+  when (t' >= t) $ do
+    observations <- view storeObservations
+    obs          <- liftIO $ readIORef observations
+    when (t' > t) $ do
+      liftIO $ writeIORef time t'
+      unless (null obs) $ do
+        liftIO $ writeIORef observations mempty
+        ms <- toMsgObs t (toList obs) $ sender m
+        yield ms
+    let obs' = fromList $ packedObsContents m
+    if synchronous m then liftIO $ modifyIORef' observations (obs' <>) else do
+      obs'' <- liftIO $ readIORef observations
+      unless (null obs'') $
+        liftIO $ writeIORef observations mempty
+      let obs''' = obs' <> obs''
+      unless (null obs''') $ do
+        ms <- toMsgObs t' (toList obs''') $ sender m
+        yield ms
diff --git a/src/Data/RTCM3/SBP/Types.hs b/src/Data/RTCM3/SBP/Types.hs
--- a/src/Data/RTCM3/SBP/Types.hs
+++ b/src/Data/RTCM3/SBP/Types.hs
@@ -31,10 +31,15 @@
 import Data.Word
 import SwiftNav.SBP
 
-type GpsTimeMap = HashMap Word16 GpsTimeNano
+type GpsTimeNanoMap = HashMap Word16 GpsTimeNano
 
-instance Hashable GnssSignal where
-  hashWithSalt s g = hashWithSalt s (g ^. gnssSignal_sat, g ^. gnssSignal_code, g ^. gnssSignal_reserved)
+instance Ord GpsTimeNano where
+  compare (GpsTimeNano tow _ns wn) (GpsTimeNano tow' _ns' wn')
+    | wn > wn'   = GT
+    | wn < wn'   = LT
+    | tow > tow' = GT
+    | tow < tow' = LT
+    | otherwise  = EQ
 
 newtype ConvertT e m a = ConvertT { unConvertT :: ReaderT e m a }
   deriving
@@ -66,8 +71,10 @@
     liftBase = liftBaseDefault
 
 data Store = Store
-  { _storeWn         :: IORef Word16
-  , _storeGpsTimeMap :: IORef GpsTimeMap
+  { _storeWn           :: IORef Word16
+  , _storeGpsTime      :: IORef GpsTimeNano
+  , _storeGpsTimeMap   :: IORef GpsTimeNanoMap
+  , _storeObservations :: IORef (Vector PackedObsContent)
   } deriving ( Eq )
 
 $(makeClassy ''Store)