Enjoy! #FF-This hashtag mostly shows up on Fridays, which should give you a good indication of what one of the Fs means. The other stands for Follow, and the two combine to make the phrase Follow Friday.. Follow Friday is essentially a Twitter holiday with the aim of getting people to follow one another.
Technical. Original manufacturers part,390 Mhz frequency, 9-volt battery operated, part number 976LM a 977LM keypad is substituted per the manufacturers change, Color: Grey Works with all Liftmaster, Sears and Chamberlain garage door openers, utilizing the 390 Mhz frequency.echnical. Original manufacturers part,390 Mhz frequency, 9-volt battery operated, part number 976LM a 977LM keypad is substituted per the manufacturers change, Color: Grey Works with all Liftmaster, Sears and Chamberlain garage door openers, utilizing the 390 Mhz frequency.
You are right, the VLF radio stations operate down to 3Hz but much lower frequencies are possible down to 1 milliHertz Ultra-low frequency these are related to events in the magnetosphere the exact mechanism is unknown. The answer by Brian Dodson gives details for the shortest wavelengths.