Alan,
Yes I too have heard some chatter about these issues...this is why I felt it important to share that which Jens had discovered.
David Bartsch
From: alanjames@xtra.co.nz
To: personal_submersibles@psubs.org
Subject: Re: [PSUBS-MAILIST] sonar self generated noise
Date: Wed, 12 May 2010 14:06:59 +1200
Hi David,
I put together a PWM motor control kit & in its instructions a capacitor & diode
are wired between the positive lead to the motor & the negative lead from the motor
(the right way round) these reduce motor hash & voltage spikes significantly.
I won't give you the values as this motor controller is only rated for 20 AMPS.
I don't know if this is done with Minnkota motors & controllers. Maybe someone will know.
but I have heard people on site complaining about motor hash from these units interfering with
other sensitive equipment.
Alan
----- Original Message -----
Sent: Wednesday, May 12, 2010 12:20 PM
Subject: [PSUBS-MAILIST] sonar self generated noise
To all:
Jens Laland found this information during research and I felt with past discussion about motor controllers and other devices causing sonar issues, this should be shared with the group.
"One of the common errors incurred with the use of hydrophones is to use a power source that is powering other (noisy) equipment. For example, the inverter on some boats may produce noise because of the modified AC waveform it produces. If a battery is being used to power the hydrophone/preamp combination, one of the worst mistakes (and easiest to rectify) is the powering of recording devices or other equipment off of the same battery. This should never be done as the motor noise from a recorder will be passed through the battery into the hydrophone and back to you (the battery acts like a capacitor, passing noise back through the circuit). If you must use the same battery, employ an automotive RF interference filtering line to your hydrophone's power (e.g. Radio Shack's #270-051)."
"A good rule of thumb is to always use a separate battery just for your hydrophones." "With pre-amplified, battery-operated hydrophones, occasionally electrical noise will also be introduced due to a difference in potential between seawater ground and the hydrophone preamp's ground (this type of noise sounds like a hum). One solution to this dilemma may be to run a wire from your battery's negative terminal into the seawater."
I have picked up radio stations without proper shielding in place and interior lighting when testing indoors as well!
David Bartsch for Jens Laland
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