According to later accounts, when the celebratory pistol was fired at midnight the sound was so strong it caused the radio transmitter's carbon microphones to "pack", thus knocking the station off the air.
San Jose Mercury Herald, December 31, 1916, page 1:

Pistol  Shot  by  Wireless  as  Old  Year  Goes

Brilliant  Chemical  Flash  From  Top  of  Bank  Building  at  12  O'Clock  Tonight  Planned.

    A unique and interesting test of the wireless telephone is to be made in this city at the instant of the passing of the old year.
    In front of the transmitter of the radio-phone will be placed a pistol which will be fired at 12 o'clock, Pacific standard time. At the same time a brilliant electro-chemical flash will be ignited on the roof of the Garden City Bank building which will be visible a long way, probably as far as the curvature of the earth will allow.
    Tests of the flash of a strength of one-hundredth were made this summer by the local wireless telephone station assisted by Mr. Campbell, son of Professor Campbell of Lick observatory, and although only a few grains were used the flash was plainly visible at both San Jose and Lick.
    As a preliminary Messers. Herrold and Portal will check their time from Arlington (eastern time) and again from Mare Island at 10 o'clock, Pacific standard time. The full strength of current will be used in the wireless telephone test and the pistol shot should be plainly heard to the full limit of distance by all stations in tune with the waves sent out from the San Jose station.