diff --git a/impl/README.md b/impl/README.md
new file mode 100644
index 0000000..c230fbe
--- /dev/null
+++ b/impl/README.md
@@ -0,0 +1,22 @@
+# Hamnet70 Implementation
+
+This directory contains an implementation of the Hamnet70 protocol.
+
+Before you can compile and use this code, some additional steps are necessary:
+
+1. Copy `src/config.h.template` to `src/config.h` and set the following variables:
+   - `MY_CALL`: the station call sign (i.e. your amateur radio call sign).
+     This will be encoded into the address fields of outgoing packets.
+2. Install dependencies:
+   - _libliquid_ compiled with _libfec_ support
+   - _libfec_
+   - _fftw3_
+   - _libhackrf_
+
+After everything is prepared, compile the code using `./make.sh`.
+Parameters to this script are forwarded to `make` so you can speed things up a little with `./make.sh -j4` (on a CPU with 4 threads).
+
+When compiled, you have two options for running Hamnet70:
+
+1. In digipeater (base station) mode: `build/hamnet70 -c`. This will broadcast beacons and wait for clients to connect.
+2. In client mode: `build/hamnet70`. This will wait for a beacon to arrive and connect to it.
diff --git a/impl/src/config.h b/impl/src/config.h.template
similarity index 95%
rename from impl/src/config.h
rename to impl/src/config.h.template
index 4abb898..b9ffc23 100644
--- a/impl/src/config.h
+++ b/impl/src/config.h.template
@@ -9,6 +9,10 @@
 
 #include <liquid/liquid.h>
 
+/*** LAYER 2 CONFIG ***/
+
+#define MY_CALL undefined  // define MY_CALL to your call sign as a C string, e.g. "DL5TKL"
+
 /*** TIMING CONFIG ***/
 
 #define TX_SWITCH_BACKOFF_PREAMBLE_MS           42   // only relevant if packet cannot be decoded (maximum packet duration)