I just tried it wrapped in foil. I didn't actually measure the spikes on th=
e frequency analysis, but they look about the same to me, and very visible =
on the spectrogram. I didn't connect the foil to common - should I have?
I also measured the voltage across the capsules. With 2 capsules per channe=
l, it's just 0.54V. I then disconnected one one each side, and the remainin=
g two had 1.32 across them. Still far short of the recommended 5V, but the =
same test with the recorder sitting right on top of the box resulted in a r=
ecording that appears to be free of the bands that were so obvious with 4 c=
apsules. Well, not free, but vastly reduced, so I imagine leaving the recor=
der close by but not actually on the box will be good enough.
I'll continue using just two capsules until I can make a battery box.
I was well aware there might be problems with four capsules from reading ol=
d postings on this list, and the information on the Frogloggers website, bu=
t I didn't expect them to manifest themselves like this.
Peter Shute
From: O=
n Behalf Of Avocet
Sent: Tuesday, 13 March 2012 11:34 AM
To:
Subject: Re: [Nature Recordists] Re: Initial SASS test shows bands of harmo=
nics
> The fact that the frequencies are spaced out by the same amount up
> the spectrum rather than being multiples is interesting.
The spectrum is multiples of 400Hz The fact that it reaches such high
multiples just indicates a time delay rather than a harmonic
resonance.
> I've just proven it's interference from the M10.
Peter,
The mic circuit will have probably picked up a pulse from the
digitiser with a delay of around 2.5ms. Any digitiser will give off a
lot of hash. This may not even be audible but had "fed forward" into
the mic and back into the digitiser with a repetition rate of 400Hz.
The answer if you want to mount the recorder in the array is probably
to screen it with foil.
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
------------------------------------
"While a picture is worth a thousand words, a
sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause.
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