Re: What causes recording rumble?

["J. Charles Holt"]

David,

It was running on battery power. I tried to get away from potential noise s=
ources, but I suppose its possible I was getting signal from somewhere in t=
he house. I=92ll try it again outside with the resistor at high gain and se=
e what I get.

=96 Charles

> On Jun 28, 2015, at 6:52 PM,  [naturerecordists] <natu=
> wrote:
>
> > Here=92s a screenshot showing the signal from the dummy mic: https://ww=
w.dropbox.com/s/tfr8kc5aii1sxlt/Rumble.jpg <https://www.dropbox.com/s/tfr8k=
c5aii1sxlt/Rumble.jpg>
>
> Charles,
>
> Looks like good old square wave mains hum with all the odd harmonics to m=
e
> going by the top frequency scale. The even harmonics cancel out in a squa=
re
> wave due to symmetry. Are you using a mains adaptor or is it near one?
>
> David Brinicombe
>
>