diff --git a/.appveyor.yml b/.appveyor.yml
index 8b4cb86..c96fd63 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -5,6 +5,7 @@ image:
 stack: python 3
 
 environment:
+  MINGW_DIR: C:\mingw-w64\x86_64-7.2.0-posix-seh-rt_v5-rev1\mingw64\bin
   PY_DIR: C:\Python37-x64
 
 clone_depth: 3
@@ -12,9 +13,15 @@ clone_depth: 3
 build: off
 
 init:
+- cmd: set PATH=%MINGW_DIR%;%PATH%
 - cmd: set PATH=%PY_DIR%;%PY_DIR%\Scripts;%PATH%
+- cmd: set CC=gcc
 
-install: pip install -e .[tests,io]
+install:
+- cmd: mingw32-make -C rnxcmp
+- sh: make -C rnxcmp
+
+- pip install -e .[tests,io]
 
 test_script: pytest -xrsv
 
diff --git a/README.md b/README.md
index 6827e50..8e5d27c 100644
--- a/README.md
+++ b/README.md
@@ -61,6 +61,22 @@ If you need to use `.crx` Hatanaka compressed RINEX, compile the `crx2rnx` code
 make install -C rnxcmp
 ```
 
+#### Windows
+Windows as usual is more difficult to compile code on.
+For optional Hatanaka converter, here are some tips.
+
+> cc -O2 source/rnx2crx.c -o rnx2crx
+process_begin: CreateProcess(NULL, cc -O2 source/rnx2crx.c -o rnx2crx, ...) failed.
+make (e=2): The system cannot find the file specified.
+
+Assuming you have 
+[installed MinGW compiler on Windows](https://www.scivision.co/windows-gcc-gfortran-cmake-make-install/):
+```posh
+set CC=gcc
+mingw32-make -C rnxcmp
+```
+
+
 ## Usage
 
 The simplest command-line use is through the top-level `ReadRinex` script.
diff --git a/georinex/io.py b/georinex/io.py
index decd667..2d59a85 100644
--- a/georinex/io.py
+++ b/georinex/io.py
@@ -58,12 +58,15 @@ def _opencrx(f: TextIO) -> str:
     Nbytes is used to read first line.
     """
     exe = './crx2rnx'
+    shell = False
     if os.name == 'nt':
         exe = exe[2:]
+        shell = True
+
     try:
         In = f.read()
         ret = subprocess.check_output([exe, '-'], input=In,
-                                      universal_newlines=True, cwd=R/'rnxcmp')
+                                      universal_newlines=True, cwd=R/'rnxcmp', shell=shell)
     except FileNotFoundError as e:
         raise FileNotFoundError(f'trouble converting Hatanka file, did you compile the crx2rnx program?   {e}')
 
diff --git a/setup.cfg b/setup.cfg
index 5ef89ec..8071c3c 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,6 +1,6 @@
 [metadata]
 name = georinex
-version = 1.6.2
+version = 1.6.3
 author = Michael Hirsch, Ph.D.
 description = Python RINEX 2/3 NAV/OBS reader with speed and simplicity.
 url = https://github.com/scivision/georinex
diff --git a/tests/test_hatanaka.py b/tests/test_hatanaka.py
index 28df63a..8617a9d 100644
--- a/tests/test_hatanaka.py
+++ b/tests/test_hatanaka.py
@@ -4,17 +4,26 @@
 from pathlib import Path
 import georinex as gr
 from datetime import datetime
-R = Path(__file__).parent
+import os
 
-try:
-    # capture_output is py >= 3.7
-    ret = subprocess.run(['crx2rnx', '-h'], stderr=subprocess.PIPE, universal_newlines=True)  # -h returncode == 1
+R = Path(__file__).parent
+Rexe = Path(__file__).resolve().parents[1] / 'rnxcmp'
+exe = './crx2rnx'
+shell = False
+if os.name == 'nt':
+    exe = exe[2:]
+    shell = True
+
+try:  # capture_output is py >= 3.7
+    ret = subprocess.run([exe, '-h'], stderr=subprocess.PIPE,
+                         universal_newlines=True, cwd=Rexe, shell=shell)  # -h returncode == 1
     nocrx = False if ret.stderr.startswith('Usage') else True
-except (FileNotFoundError, PermissionError):
+except (FileNotFoundError, PermissionError) as e:
+    print(e)
     nocrx = True
 
 
-@pytest.mark.skipif(nocrx, reason='crx2rnx not found')
+@pytest.mark.skipif(nocrx, reason=f'crx2rnx not found in {Rexe}')
 @pytest.mark.timeout(30)
 def test_obs3():
     fn = R / 'CEBR00ESP_R_20182000000_01D_30S_MO.crx.gz'
diff --git a/tests/test_nav2.py b/tests/test_nav2.py
index 6200f19..8b44473 100644
--- a/tests/test_nav2.py
+++ b/tests/test_nav2.py
@@ -10,6 +10,8 @@
 
 
 def test_time():
+    pytest.importorskip('unlzw')
+
     times = gr.gettime(R/'ab422100.18n.Z').values.astype('datetime64[us]').astype(datetime)
 
     assert times[0] == datetime(2018, 7, 29, 1, 59, 44)
@@ -17,6 +19,8 @@ def test_time():
 
 
 def test_data():
+    pytest.importorskip('unlzw')
+
     nav = gr.load(R/'ab422100.18n.Z')
 
     nav0 = nav.sel(time='2018-07-29T03:59:44').dropna(dim='sv', how='all')
@@ -43,6 +47,8 @@ def test_mangled():
 
 
 def test_tlim():
+    pytest.importorskip('unlzw')
+
     nav = gr.load(R/'ceda2100.18e.Z', tlim=('2018-07-29T11', '2018-07-29T12'))
 
     times = nav.time.values.astype('datetime64[us]').astype(datetime)
@@ -57,6 +63,8 @@ def test_tlim():
 
 
 def test_galileo():
+    pytest.importorskip('unlzw')
+
     nav = gr.load(R/'ceda2100.18e.Z')
 
     E18 = nav.sel(sv='E18').dropna(dim='time', how='all')
@@ -72,6 +80,8 @@ def test_galileo():
 
 
 def test_gps():
+    pytest.importorskip('unlzw')
+
     nav = gr.load(R/'brdc2800.15n.Z')
 
     times = nav.time.values.astype('datetime64[us]').astype(datetime).tolist()
diff --git a/tests/test_nav3.py b/tests/test_nav3.py
index be2f979..7c8fad9 100644
--- a/tests/test_nav3.py
+++ b/tests/test_nav3.py
@@ -33,6 +33,8 @@ def test_tlim():
 def test_qzss():
     """./ReadRinex.py -q tests/qzss3.14n -o r3qzss.nc
     """
+    pytest.importorskip('netCDF4')
+
     truth = gr.load(R/'r3qzss.nc')
     nav = gr.load(R/'qzss3.14n')
     assert nav.equals(truth)