Bose A20 mic too sensitive for Skyview HDX

[Alto]

When I press push to talk and transmit the side tone picks up my voice and white noise, that I think may be environmental. I’m wondering if turning down the microphone gain would help, but in the com setup, mic gain is greyed out and can’t be adjusted.

When the motor isn’t running, the white noise isn’t there. When engine is running on the ground the white noise is less then when in flight.

Has anyone a suggestion on how to adjust this?

 

[Rhino]

Sidetone is unaffected by mic gain, so this very likely isn't a solution.

Do you have a 425 radio? If not, that's probably why it's greyed out.

You've confirmed this happens only with the A20, and not other headsets?

 

[Alto]

Thanks for the reply.

I believe the radio is the SV-Com X25.

I only have LEMO jacks and I haven’t tried other headsets.

What I’m experiencing is white noise simultaneous with the sound of my voice when transmitting, but not when the cabin is quiet, i.e. Engine not running, on the ground. That’s why I think the noise in the cabin is being picked up by the microphone when I press the PTT. Is there a way to make the microphone pic up less wind noise/cabin noise or is my only option a bigger mic muff?

 

[Alto]

I would like to add, that the white noise is wholly absent from intercom conversation.

 

[Rhino]

Mic gain only works on the 425, so that explains why yours is greyed out.

You very likely are getting induced noise from your ignition system, probably in the wiring between the intercom and radio. You might want to review this:

Ground Loops and Noise in Aircraft Systems

Quite a few forum threads and articles have at various times addressed ground loops, and their potential to cause noise or other interference in your avionics system. Simply put, a ground loop occurs when different paths to ground are used. The difference in resistance, or impedance, on those...

forum.flydynon.com

I seriously doubt it's your headset. But if you can find a different one with LEMO jacks, it wouldn't hurt to confirm that.

 

[Alto]

Maybe I have the X83 instead of the X25. There doesn’t appear to be an external visible difference. The set up picture I posted above indicates 8.33 kHz frequency spacing.

Am I correct in interpreting your statement that mic gain is on the X25, but not the X83?

If it is on the X83 too, do you know where the mic gain is located in the Skyview HDX menu system. Or for that matter, where is the radio selected. Maybe the wrong radio is configure? Why does it say in parentheses (sv com-425/t25/t8) after the squelch setup?

I guess I can experiment and sound insulate the mic, and press the PTT to see if the noise persist.

 

[jnmeade]

I have two planes with HDX and I fly with LEMO headsets in both. A Bose A20 in one and a Lightspeed something in the other. I don't have the phenomenon you describe in either plane with either headset. I have 2 SV-COM 25s and Dual 10" HDX in the Lightspeed plane and one 10" HDX with I think an SV-COM 25 in the Bose plane.

 

[Rhino]

...Am I correct in interpreting your statement that mic gain is on the X25, but not the X83?...

...I guess I can experiment and sound insulate the mic, and press the PTT to see if the noise persist...

Sorry. Mistake in typing. Only the SV-COM-425 has mic gain. If you don't have the 425, that probably explains why it's greyed out.

It isn't audio sound originating from your microphone. You'd hear it without headsets if that was the case. If the noise is varying with engine RPM, it's almost certainly induced electrical noise being picked up by your wiring or equipment somewhere. You probably have a ground loop, aren't using a common ground for your systems, or don't have a shielded cable or cables where you need them.

 

[Alto]

Thank you for all that information.

I do have a landing height system with shielded audio wire connected to the pin 17 of a SV-intercom-2S. The shield Is grounded to pin 1. The power wire for the LHS is also shielded, but the shield isn’t grounded.

The only time noise is heard is when PTT is pressed.

Do you think grounding the shielding of the power wire will stop the noise?

 

[Rhino]

I'm confused. You cite a landing height system input, which should be audio. Then you ask about shield for a power wire, which is not audio. Are we talking about two different things here?

You might be able to simply disconnect the height system to confirm it isn't the source.

Is this a new Dynon system install, or a new problem on an existing system that was never seen before?

You don't by any chance have any ferrites in your wiring, do you?

 

[Alto]

The landing height system, has multiple wires, an audio shielded, a power shielded, a ground and a data, for gps input. It uses LIDAR for measurement.

Would simply turning off the intercom rule out the connections to it as a source?

It is an aircraft that’s almost a year old. I’ve lived with the noise when transmitting up to this point, while addressing other things and becoming more proficient in it’s Flight characteristics and system operation, including the use of Skyview HDX. Rotorcraft flight was new to me.

I like the Skyview HDX system and I’m planing replacement of the Garmin system in my high performance fixed wing, when the autopilot is certified.

I’ve had the dropped wifi connection issue with my iPad, and this noise, but otherwise I’ve been pleased with it.

 

[Rhino]

Ground all shields at the intercom, and make sure they are not grounded at the other end.

The LHS doesn't get power from the intercom, does it? That should be a separate line to a different destination.

Turning off the intercom would not rule out any connections. The noise might go away, but you won't know why. Try the Lightspeed headset. If nothing else, you will have eliminated something. But I think you're going to have to get into the wiring to figure this out.

Can the LHS be disconnected with a connector at the other end without breaking wires? Would help eliminate that.

And what exactly is the LHS?

 

[Alto]

The LHS has a plug about 3 inches from the device that can be disconnected. The wires to the intercom and power and ground are less than 4 feet in length. I never connected the data feed to the Skyview.

I obtained the power from tapping into an accessory electrical outlet used to power the iPad.

Here is a link to the LHS

Landing Height System (LHS-200-B) – Landing Height System for Certified Airplanes

landingheight.com

My next door hanger neighbor uses a Lightspeed I’ll ask if I can use it to provide a test.

You consider it more desirable to ground the shielding for the LHS power wire to pin one on the intercom then to the airframe ground?



Thanks for all these suggestions.

 

[Alto]

I’m back from flying today and here’s what I found out. I removed the A20 headset I have been using and the problem went away. Useing an older bose aviation X headset and my voice sounds clear when transmitting. Useing the A20 from my other aircraft and no problem either.

This and a poping noise I was also experiencing when the headset cable moved, that I had assumed was from the jack all apears to be poor quality control from Bose And due to the headset itself.

 

[Rhino]

Glad you found the source. Is the headset still under warranty?

 

[Alto]

A Google search states they have a 5 year warranty, so sh be so. We’ll see.

 

[Alto]

I’m going to fly with it in the other plane and see if the problem shows up there, before returning it.