CAMBRIDGE — John, a merchant cleaning out his garage at the behest of his wife, set up a table early Sunday morning on Albany Street. On this table one could find a smorgasbord of electronic parts and old computer chipsets next to a tray of wrenches and hammers, all of which were for sale at modest prices. Once he was set up, he sat down listening to an old radio — no word on if it, too, was for sale — and waited for customers to start rolling in. In the background, the hammering of a typewriter could be heard next to a demonstration booth for the old Enigma computer. John was one of hundreds of buyers and sellers who flocked to the MIT campus for the MIT Radio Society’s Swapfest held Sunday, Oct. 21.