[time-nuts] 50 and 60 Hz as frequency reference

[Magnus Danielson]

Dear time-nuts,

This discussion of frequency of mains network makes me recall that my 
HP521C counter is built such that it uses the mains network as reference 
unless one has the high precision crystal option, a 100 kHz crystal 
divided down to 100 Hz.

It uses the 50, 60 or 100 Hz signals to divide down to 10 Hz using a 
phantastron divider. You can trim the division ration on the backside on 
a potentiometer.

The 100 kHz crystal is divided down to 100 Hz using phantastron dividers 
too.

The display using neon lamps lighting up the matching digit. Very neat 
display.

Unfortunately I don't have space to have it neatly located in the 
measurement rig, as there is too many other instruments in it. But on 
occasion I dig it up and play with it. :)

I thought this historic reference could be nice when discussing 50 and 
60 Hz absolute frequency and deviation.

Cheers,
Magnus