Setting up GQRX to listen to railroad frequencies

While this isn't directly related to timestampSDR it is a common use case, so I thought I would explain how I set it up. This doesn't cover the initial installation of GQRX, or getting it to recognize your particular SDR, as that is well documented already. So, once you've gotten those things taken care of:

• Click Input controls (E). Look up for the Hardware AGC checkbox, and make sure it is selected. You're done with input controls now, so click back to Receiver options (also in E)
  • If you're using an older version of GQRX there is an issue where Hardware AGC will no longer be selected when you restart the application. This issue is resolved in GQRX v2.11
• Enter the frequency you want to listen to in (A)
• Select Narrow FM in Mode (C)
• Turn your speakers down a bit and click the play button in the upper left. You'll get static at first.
• Look at the dBFS value in B. Set your Squelch (D) to be a little above that (remembering that these are negative values).
  • Getting your squelch just right will take some work. If you set it too low you'll miss transmissions, if you set it too high you'll get static and poor transmissions. For me, setting it about ~7dB above the value in B seems to work well.