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
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | 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<fransew@gmail.com> wrote: -->
AeroElectric-List message posted by: "user9253" <fransew@gmail.com>
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
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: 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
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Insulating washers [was: Radio noise when transmitting] |
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
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|