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slsaowner
Joined: 28 Oct 2006
Posts: 80
Location: WI
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| Posted: Mon Mar 16, 2009 4:00 pm Post subject: Hiss in the headphones in a Rotax-powered airplane |
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| I have recently noticed an annoying hiss in the headphones installed in my Rotax-powered plane. It is equally loud on both radios, but loudness seems to be rpm-dependent. and non-existent at idle power. There's no change in the "frequency" of the sound when RPM changes, only the volume. Anybody have any idea what's going on? |
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rfane
Joined: 26 Apr 2006
Posts: 214
Location: Sunnyvale, CA
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| Posted: Tue Mar 17, 2009 7:32 am Post subject: |
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| If this came up without adding any additional equipment, I would look for a loose ground connection. |
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rsteele
Joined: 12 Feb 2007
Posts: 259
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| Posted: Tue Mar 17, 2009 1:22 pm Post subject: |
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I agree, a bad ground is the usual cause, but it can also be a ground loop, where both ends of a shield ground are connected to ground when it should be just one end. I fly behind a Rotax and have never had a problem.
A side node/example. I just bought a new pickup. It has a jack to listen to my IPod, which is great, but when I set my IPod on the charger (in the cigarette lighter) there is a very annoying hiss. I'm sure it's a ground loop and this in a 2009, brand new vehicle. Without being in the charger it works great.
Ron |
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slsaowner
Joined: 28 Oct 2006
Posts: 80
Location: WI
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| Posted: Fri Apr 10, 2009 8:59 am Post subject: Hiss in the headphones |
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| I think what I'm hearing is noise picked up by the mike - a David Clark electret - because when I wrap my hand around it the "hiss" goes away. It's as though the mike is picking up the sound of air rushing by the cockpit, a combination of propwash and slipstream air. |
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CharlieTango
Joined: 10 Jun 2006
Posts: 614
Location: Mammoth Lakes, California
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| Posted: Fri Apr 10, 2009 10:34 am Post subject: |
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| maybe your intercom squelch? |
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slsaowner
Joined: 28 Oct 2006
Posts: 80
Location: WI
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| Posted: Sat Apr 11, 2009 7:39 am Post subject: Hiss in the headphones |
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| Yeah, I've been thinking the very same thing. I'll check it out next time I fly. |
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flyboy2007
Joined: 27 Jan 2008
Posts: 73
Location: wisconsin
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| Posted: Sat Apr 11, 2009 8:45 am Post subject: |
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| (a David Clark electret ) Just in my opinion this is a lot of your problem. I have had david clarks and every set I have had were JUNK! I got a nice set of avcomm and they work excellent and are about half the price. Just My oppinion. |
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slsaowner
Joined: 28 Oct 2006
Posts: 80
Location: WI
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| Posted: Thu Jun 11, 2009 8:21 am Post subject: Hiss in the headphones |
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| It was the squelch - squelch knob was turned all the way down. |
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