---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Tue 03/17/20: 3 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:09 AM - Re: Re: Radio noise when transmitting (Ernest Christley) 2. 10:13 AM - Re: Radio noise when transmitting (Robert L. Nuckolls, III) 3. 01:39 PM - Re: Insulating washers [was: Radio noise when transmitting] (Joe Dubner) ________________________________ Message 1 _____________________________________ Time: 06:09:37 AM PST US From: Ernest Christley Subject: Re: AeroElectric-List: Re: Radio noise when transmitting Also, try adjusting the volume on your headset, if it has a volume control. I had an issue of a squeal on transmit. I think the headset was picking up the transmitted signal and amplifying it back out. Problem went away when I turned the headset volume down Sent from Yahoo Mail on Android On Mon, Mar 16, 2020 at 7:27 PM, user9253 wrote: --> AeroElectric-List message posted by: "user9253" Make sure that the microphone jacks are electrically insulated from the air frame with dielectric washers.=C2- The mic ground wire should be grounded at th e radio end only. -------- Joe Gores ________________________________ Message 2 _____________________________________ Time: 10:13:04 AM PST US From: "Robert L. Nuckolls, III" Subject: Re: AeroElectric-List: Radio noise when transmitting At 01:39 PM 3/16/2020, you wrote: >I have an RV 9A aircraft with a 60 amp Plane Power alternator and an >Icom IC-200 radio. I recently installed ADSB (echo UAT/FYX-EXT) >with associated antennae at recommended spacing on the plane's >belly. My recent symptoms are a high whine in the headset when >transmitting on the radio. I hear incoming radio transmissions >clearly. I checked disconnecting the alternator by opening the >field circuit breaker and the sound during transmitting goes away. >This issue may be more noticeable while on the ground. When >announcing "ready for take-off" I get a response from fellow pilots >in the pattern that they hear a high whine in the >transmission. However when at 3000 ft altitude and 5 miles from the >field during a radio check, the sound in my head set is diminished >and the response from fellow pilots is "loud and clear". The fact >that this occurred after the ADSB installation may be unrelated. I >don't remember this problem immediately after that installation, so >this may be a canard. Any advice on how to trouble shoot this and >recommended fixes that I could attempt. >Thanks to this group. I enjoy and appreciate the knowledge and >experience of the members. >Mark Donahue >206 755 1093 Make sure that the microphone jacks are electrically insulated from the airframe with dielectric washers. The mic ground wire should be grounded at the radio end only. -------- Joe Gores Joe's suggestion is a good one. Alternator whine is almost always conducted into transmitted audio by a ground loop caused by mounting the microphone jack to airframe without and insulating washer. https://tinyurl.com/t4kveee A possible reason for the noise going away while airborne: Alternator currents flowing on the airframe are greatest when alternator loads are heavy. Just after start, the battery is being recharged which adds to noise source. After a few minutes recharge, airframe currents are reduced. If you already have these washers, then the hypothesis is moot. Diode failures are rare. Let us know what you discover. Bob . . . ________________________________ Message 3 _____________________________________ Time: 01:39:38 PM PST US Subject: AeroElectric-List: Re: Insulating washers [was: Radio noise when transmitting] From: Joe Dubner Robert L. Nuckolls, III wrote on 3/17/2020 10:07: > ?? ... > ground loop caused by mounting the microphone > ?? jack to airframe without and insulating washer. > > https://tinyurl.com/t4kveee > > ?? ... Yikes, those are some expensive pieces of phenolic! Not in terms of other airplane parts measured in AMU ($1000 bills) of course but certainly in terms of dollars per ounce. In the past a friend has turned some on his lathe from some phenolic stock I had on hand. Like nearly all machining operations, the setup is time consuming but "production" is quite speedy. I have also used 0.062-inch printed circuit board material (after cleaning off the traces) to fabricate a rectangular strip that would mount jacks through oversize clearance holes. Image attached. The latter technique works for 1/8-inch jacks where no insulated mount is available AFAIK. -- Joe RV-8A Independence, OR ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.