[time-nuts] 60 Hz frequency and phase measurement

[jimlux]

On 7/2/19 11:47 PM, Hal Murray wrote:
> 
> jimlux at earthlink.net said:
>> Actually, it's because someone asked me about a science experiment where
>> you'd place them in a neighborhood outdoors.
> 
> Sounds like another science experiment: build an antenna to pick up 60 Hz.
> 
> You could start with the typical ferrite, coil, and cap.  Just adjust the cap to your new target frequency.  Simple to try.

I ran through some quick calculations on that - unlike for AM band, you 
need a fairly good sized capacitor. I think it's doable. A typical 
loopstick for AM is around 0.5 to 1 mH, so you'd need about 7000 
microfarads to resonate it at 60Hz. So, a LOT more turns on that inductor.



And then you have to start worrying about phase shift - it's going to be 
a fairly high Q resonant circuit, with the phase varying most rapidly 
around resonance.

So a resonant antenna probably isn't the way to go..

The whole goal is to look for phase shifts after all.

That's why I was thinking about magnetic field sensors..

The little electronic compass sensors sample at 100-300 Hz and have 
sensitivities comparable to the Earth's field (i.e. something like 2 
Gauss, 200 microTesla, full scale).

I don't know that they're sensitive enough - I recall that typical line 
frequency fields are in the "single digit milliGauss" range. If I 
convert that the E field, I get "single digit Volts/meter" - which is 
consistent with my tens of mV holding the scope probe in my hand.

Well... since it's a holiday weekend, it's time to break out the Beagles 
and Teensys and do some experiments. It's just that I don't like E field 
sensors (if for no other reason than High Z amplifiers get destroyed by 
ESD)..



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