diff --git a/charon_vna/io_.py b/charon_vna/io_.py
new file mode 100644
index 0000000..bfa641a
--- /dev/null
+++ b/charon_vna/io_.py
@@ -0,0 +1,12 @@
+from pathlib import Path
+
+import skrf as rf
+import xarray as xr
+from util import net2s
+
+
+# scikit-rf has no way to save files aside from touchstone and pickle
+def cal2zarr(cal: rf.calibration.Calibration, outpath: Path):
+    ideals = [net2s(net) for net in cal.ideals]
+    measured = [net2s(net) for net in cal.measured]
+    # s.to_zarr(outpath)
diff --git a/charon_vna/util.py b/charon_vna/util.py
new file mode 100644
index 0000000..e510d71
--- /dev/null
+++ b/charon_vna/util.py
@@ -0,0 +1,79 @@
+import numpy as np
+import skrf as rf
+import xarray as xr
+
+HAM_BANDS = [
+    [135.7e3, 137.8e3],
+    [472e3, 479e3],
+    [1.8e6, 2e6],
+    [3.5e6, 4e6],
+    [5332e3, 5405e3],
+    [7e6, 7.3e6],
+    [10.1e6, 10.15e6],
+    [14e6, 14.35e6],
+    [18.068e6, 18.168e6],
+    [21e6, 21.45e6],
+    [24.89e6, 24.99e6],
+    [28e6, 29.7e6],
+    [50e6, 54e6],
+    [144e6, 148e6],
+    [219e6, 220e6],
+    [222e6, 225e6],
+    [420e6, 450e6],
+    [902e6, 928e6],
+    [1240e6, 1300e6],
+    [2300e6, 2310e6],
+    [2390e6, 2450e6],
+    [3400e6, 3450e6],
+    [5650e6, 5925e6],
+    [10e9, 10.5e9],
+    [24e9, 24.25e9],
+    [47e9, 47.2e9],
+    [76e9, 81e9],
+    [122.25e9, 123e9],
+    [134e9, 141e9],
+    [241e9, 250e9],
+    [275e9, np.inf],
+]
+
+
+def db10(p):
+    return 10 * np.log10(np.abs(p))
+
+
+def db20(p):
+    return 20 * np.log10(np.abs(p))
+
+
+def minmax(x):
+    return (np.min(x), np.max(x))
+
+
+def s2net(s: xr.DataArray) -> rf.Network:
+    net = rf.Network(frequency=s.frequency, f_unit="Hz", s=s)
+    return net
+
+
+def net2s(net: rf.Network) -> xr.DataArray:
+    port_tuples = net.port_tuples
+
+    m = list(set(t[0] for t in port_tuples))
+    m.sort()
+    m = np.array(m)
+    m += 1  # skrf uses 0-indexed ports
+
+    n = list(set(t[0] for t in port_tuples))
+    n.sort()
+    n = np.array(n)
+    n += 1  # skrf uses 0-indexed ports
+
+    s = xr.DataArray(
+        net.s,
+        dims=["frequency", "m", "n"],
+        coords=dict(
+            frequency=net.f,
+            m=m,
+            n=n,
+        ),
+    )
+    return s
diff --git a/charon_vna/vna.py b/charon_vna/vna.py
index bb05cd2..5513fc1 100644
--- a/charon_vna/vna.py
+++ b/charon_vna/vna.py
@@ -1,21 +1,18 @@
 # %% imports
 import copy
-import time
 from pathlib import Path
 from typing import Optional
 
 import adi
 import iio
-import matplotlib as mpl
 import numpy as np
 import skrf as rf
 import xarray as xr
 from matplotlib import pyplot as plt
-from matplotlib.gridspec import GridSpec
-from matplotlib.patches import Circle
 from matplotlib.ticker import EngFormatter
 from numpy import typing as npt
 from scipy import signal
+from util import HAM_BANDS, db20, net2s, s2net
 
 dir_ = Path(__file__).parent
 
@@ -47,18 +44,6 @@ def get_config(sdr: adi.ad9361):
     return config
 
 
-def db10(p):
-    return 10 * np.log10(np.abs(p))
-
-
-def db20(p):
-    return 20 * np.log10(np.abs(p))
-
-
-def minmax(x):
-    return (np.min(x), np.max(x))
-
-
 def generate_tone(f: float, N: int = 1024, fs: Optional[float] = None):
     if fs is None:
         fs = sdr.sample_rate
@@ -217,7 +202,7 @@ reference_sparams = None
 reference_sparams = dir_ / "RBP-135+_Plus25degC.s2p"
 if reference_sparams is not None:
     ref = rf.Network(reference_sparams)
-    rbp135 = xr.DataArray(ref.s, dims=["frequency", "m", "n"], coords=dict(frequency=ref.f, m=[1, 2], n=[1, 2]))
+    rbp135 = net2s(ref)
 
     axs[0].plot(rbp135.frequency, db20(rbp135.sel(m=1, n=1)), label="Datasheet")
     axs[1].plot(rbp135.frequency, np.rad2deg(np.angle(rbp135.sel(m=2, n=1))), label="Datasheet")
@@ -227,15 +212,8 @@ if reference_sparams is not None:
 plt.show()
 
 
-# %%
-def s2net(s: xr.DataArray) -> rf.Network:
-    net = rf.Network(frequency=s.frequency)
-    net.s = s.data
-    return net
-
-
 # %% SOL calibration
-cal_frequency = np.linspace(70e6, 600e6, 2001)
+cal_frequency = np.linspace(70e6, 600e6, 101)
 ideal_cal_frequency = rf.Frequency(np.min(cal_frequency), np.max(cal_frequency), len(cal_frequency))
 input("Connect SHORT and press ENTER...")
 short = vna_capture(frequency=cal_frequency)
@@ -258,41 +236,6 @@ calibration = rf.calibration.OnePort(
 # %%
 s = vna_capture(frequency=cal_frequency)
 
-# %%
-ham_bands = [
-    [135.7e3, 137.8e3],
-    [472e3, 479e3],
-    [1.8e6, 2e6],
-    [3.5e6, 4e6],
-    [5332e3, 5405e3],
-    [7e6, 7.3e6],
-    [10.1e6, 10.15e6],
-    [14e6, 14.35e6],
-    [18.068e6, 18.168e6],
-    [21e6, 21.45e6],
-    [24.89e6, 24.99e6],
-    [28e6, 29.7e6],
-    [50e6, 54e6],
-    [144e6, 148e6],
-    [219e6, 220e6],
-    [222e6, 225e6],
-    [420e6, 450e6],
-    [902e6, 928e6],
-    [1240e6, 1300e6],
-    [2300e6, 2310e6],
-    [2390e6, 2450e6],
-    [3400e6, 3450e6],
-    [5650e6, 5925e6],
-    [10e9, 10.5e9],
-    [24e9, 24.25e9],
-    [47e9, 47.2e9],
-    [76e9, 81e9],
-    [122.25e9, 123e9],
-    [134e9, 141e9],
-    [241e9, 250e9],
-    [275e9, np.inf],
-]
-
 # %%
 s_calibrated = calibration.apply_cal(s2net(s))
 
@@ -302,7 +245,7 @@ s_calibrated.plot_s_smith()
 plt.show()
 
 plt.figure()
-for start, stop in ham_bands:
+for start, stop in HAM_BANDS:
     plt.axvspan(start, stop, alpha=0.1, color="k")
 s_calibrated.plot_s_db()
 # ref.plot_s_db(m=1, n=1)
@@ -312,7 +255,7 @@ plt.xlim(s_calibrated.f[0], s_calibrated.f[-1])
 plt.show()
 
 plt.figure()
-for start, stop in ham_bands:
+for start, stop in HAM_BANDS:
     plt.axvspan(start, stop, alpha=0.1, color="k")
 # s_calibrated.plot_s_vswr()
 # drop invalid points