Hi all,

I live in the Boston area and I like to listen to VHF aircraft comms.
I noticed something odd recently, though: it appears that Boston
Approach is using duplex comms. I hear only the ground to air side of
the communication on 124.4MHz and then an immediate reply from the
aircraft on 133.0 MHz. I found this by chance because I had heard
traffic on both of those frequencies while scanning around and finally
started switching between them.

I had thought that the VHF air band was simplex. A quick web search
didn't yield any answers.

Anyone know what is going on here?

Thanks,

Sean
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