diff --git a/zk/Antenna_gain_and_ERP.md b/zk/Antenna_gain_and_ERP.md
new file mode 100644
index 0000000..97afbb7
--- /dev/null
+++ b/zk/Antenna_gain_and_ERP.md
@@ -0,0 +1,48 @@
+---
+tags: [radio, ham-study]
+---
+
+[Antennas](./Types_of_antenna.md) like the Yagi have **gain**. This means they
+can increase the power that they receive from the transmitter via the
+[feeder](./Feeders.md).
+
+Gain is measured in decibels:
+
+| Antenna gain | Power muliplied by a factor of... |
+| ------------ | --------------------------------- |
+| 3dB          | 2                                 |
+| 6dB          | 4                                 |
+| 9dB          | 8                                 |
+| 10dB         | 10                                |
+
+ERP is the **Effective Radiated Power**. This is the product of the power that
+the antenna is receiving from the feeder and the gain level.
+
+> ERP (Watts) = power feed x antenna gain
+
+Some example calculations:
+
+| Gain | Gain times | Power to antenna | ERP       |
+| ---- | ---------- | ---------------- | --------- |
+| 3dB  | x2         | 10 watts         | 20 watts  |
+| 6dB  | x4         | 10 watts         | 40 watts  |
+| 9dB  | x8         | 10 watts         | 80 watts  |
+| 10dB | x10        | 10 watts         | 100 watts |
+
+### ERIP
+
+ERP is calculated relative to the half-wave dipole. This is the benchmark. The
+power that would be generated using this type of antenna.
+
+But, as noted above, the dipole has a distinct radiation pattern - diffusing in
+poles at right angles to the horizontal plane of the antenna.
+
+By being tied to the dipole, ERM is therefore not the most universal or
+objective unit of measurement.
+
+To remedy this, there is another unit: ERIP. This stands for **Effective
+Isotropic Radiated Power**. It's the same calculation but it uses a theoretical
+antenna that would radiate equally in all directions as the benchmark.
+
+Because of the equal radiation pattern in all directions, EIRP will always be
+higher than ERP. Roughly speaking, 10 Watts in EIRP would be 6 Watts in ERP.
diff --git a/zk/Antenna_polarisation.md b/zk/Antenna_polarisation.md
new file mode 100644
index 0000000..b05a47d
--- /dev/null
+++ b/zk/Antenna_polarisation.md
@@ -0,0 +1,12 @@
+---
+tags: [radio, ham-study]
+---
+
+**Polarisation** means whether the antenna is positioned on a vertical or
+horizontal plane.
+
+Of the antennas covered at foundation level, only dipoles and Yagis can be
+positioned at variable polarities.
+
+VHF and UHF are received most effectively when the transmitter and receiver have
+the same antenna polarisation.
diff --git a/zk/Antennas.md b/zk/Types_of_antenna.md
similarity index 51%
rename from zk/Antennas.md
rename to zk/Types_of_antenna.md
index 7fd945a..ea04bc1 100644
--- a/zk/Antennas.md
+++ b/zk/Types_of_antenna.md
@@ -75,60 +75,3 @@ In contrast to the others, the Yagi is directional and focused in one direction
 It basically works as a dipole with a reflector behind it. This helps to push
 the waves in the horizontal direction of travel, assisted by the director spoke
 in front.
-
-### Gain and ERP
-
-Antennas like the Yagi have **gain**. This means they can increase the power
-that they receive from the transmitter via the [feeder](./Feeders.md).
-
-Gain is measured in decibels:
-
-| Antenna gain | Power muliplied by a factor of... |
-| ------------ | --------------------------------- |
-| 3dB          | 2                                 |
-| 6dB          | 4                                 |
-| 9dB          | 8                                 |
-| 10dB         | 10                                |
-
-ERP is the **Effective Radiated Power**. This is the product of the power that
-the antenna is receiving from the feeder and the gain level.
-
-> ERP (Watts) = power feed x antenna gain
-
-Some example calculations:
-
-| Gain | Gain times | Power to antenna | ERP       |
-| ---- | ---------- | ---------------- | --------- |
-| 3dB  | x2         | 10 watts         | 20 watts  |
-| 6dB  | x4         | 10 watts         | 40 watts  |
-| 9dB  | x8         | 10 watts         | 80 watts  |
-| 10dB | x10        | 10 watts         | 100 watts |
-
-### ERIP
-
-ERP is calculated relative to the half-wave dipole. This is the benchmark. The
-power that would be generated using this type of antenna.
-
-But, as noted above, the dipole has a distinct radiation pattern - diffusing in
-poles at right angles to the horizontal plane of the antenna.
-
-By being tied to the dipole, ERM is therefore not the most universal or
-objective unit of measurement.
-
-To remedy this, there is another unit: ERIP. This stands for **Effective
-Isotropic Radiated Power**. It's the same calculation but it uses a theoretical
-antenna that would radiate equally in all directions as the benchmark.
-
-Because of the equal radiation pattern in all directions, EIRP will always be
-higher than ERP. Roughly speaking, 10 Watts in EIRP would be 6 Watts in ERP.
-
-## Antenna polarisation
-
-**Polarisation** means whether the antenna is positioned on a vertical or
-horizontal plane.
-
-Of the antennas covered at foundation level, only dipoles and Yagis can be
-positioned at variable polarities.
-
-VHF and UHF are received most effectively when the transmitter and receiver have
-the same antenna polarisation.