Note that airnav doesn't include the ".51" in their database. For
instance, COR is at 205.51, but listed as 205 on airnav.

Also not that many military beacons are not listed on either the FCC
database or airnav. I have three examples, namely
xsd 278Khz Tonopah Test Range, Nevada
pyd 414kHz, Groom Lake, Nevada
aec 209khz Basecamp, Nevada (a cool NDB with voice on it)