diff --git a/GPS-Sim.md b/GPS-Sim.md
index cc8b61b..4b614fa 100644
--- a/GPS-Sim.md
+++ b/GPS-Sim.md
@@ -3,9 +3,12 @@ This app allows you to broadcast GPS baseband signal data streams.
 ## Generator
 You can use [gps-sdr-sim](https://github.com/osqzss/gps-sdr-sim) to generate data for this app.  
 
-`gps-sdr-sim -e brdc3540.14n -l LAT,LONG,HEIGHT -o BBD_NNNN.C8`
+`gps-sdr-sim -e RINEX_NAVIGATION_FILE -l LAT,LONG,HEIGHT -o BBD_NNNN.C8`
 That will create `BBD_NNNN.C8`, but note that you also need to specify its sample rate and frequency in another file, as explained below.
 
+### RINEX navigation file for GPS ephemerides
+Download the latest file for this parameter directly from Nasa: https://cddis.nasa.gov/archive/gnss/data/daily/
+
 ### Sample rate and frequency specification
 Create `BBD_NNNN.TXT` with:
 ```