Sorry, but you are slightly wrong.
The frequency is 131.78333 as previously stated.
That equates to a "channel" (as keyed on aircraft radios of "131.785").
Your previous post suggest you misunderstand 8.33 channels and assumed I had mistyped 131.875.
Not surprisingly you heard nothing on 131.875.
Most scanners are designed for 25k AM bandwidth, and if you tune 8.33 kHz away from the true freq, you will still hear the signal!
Hence your belief that you are receiving 131.775.
This may help you understand how 8.33 channels are numbered:http://www.eurocontrol.int/sites/defaul ... 0table.pdf
I have an SDR shot of a BA transmission to show this, but this forum doesn't allow attachments