Sonex is too noisy for radio on climb out

[pgerhardt]

Using an Icom A-21 I have had several instances of transmitting a carrier but no audio. I am attributing this to poor connections with the headset adapter. I can see the transmit indicator on the LCD of the handheld but others do not always hear me. Wiggling the wires will restore the proper operation.

When working I usually get loud and clear reports on the ground. I have checked the radio on a communications monitor for proper freq and modulation, rx sensitivity and have checked my antenna with an antenna analyzer. The SWR is about 1.4 to 1 which is about right.

When I st checked out my chinese aviation headset I did get some RF feedback into the radio. The antenna is only like a foot from your headset. This caused a squeal in the audio even with the engine off and on the ground. This would change as one moved the wires around. I took the headset home and put a small capacitor across the mic element right in the mic itself this seems to have helped. I forgot the value of the cap but maybe a 220pf or 380pf small with leads soldered right on to the mic element.

Now I do get "I can barely understand you" reports from ATC at times (when under cruise condx) Other times it seems ok.

The sonex cockpit is very noisy. Some radios cope better and I think the MGL V6 might have one of the best. I think that a noise cancelling mic is a help. Noise cancelling on the electret mics is mostly a function of the mechanical construction of the mic housing. As I understand it the mic holder tries to let the ambient noise in the back with a small hole and the voice through the front. The difference between the voice and the ambient noise gets better (better S/N ration). I could be wrong I am not an engineer, nor did I stay at a Holiday Inn last night. I think I would benefit by adjusting the mic gain. On the Icom HT A-21 there is a mic gain and a modulation gain but they are internal adj and I have not tried them. Like I said they seem to be set perfect on the communications analyzer. I believe it might be beneficial to turn down the mic gain and this MIGHT yield a better S/N ratio. I think this is what happens with the MGL V-6.

As far as receiving I purchased a Headsets Inc. kit for my Chinese headset which replaces the speakers with 'real' electronic noise reduction units. When I turn this on the noise drops maybe 20db and I can actually understand everything on the radio. These are under $200 and work great. http://www.headsetsinc.com/ANR_kits.html

Next I may try the internal adj and turn the mic gain down a bit.

I think the ambient noise of the A/C is the main problem, if there is no RF getting into your wires, the antenna is ok with low SWR, the DC power is clean, try turning the mic gain down and talk loud to make up the diff, this will increase the S/N ratio on the xmit signal.

Try real ANR to help the receive, it makes a huge difference.

Let us know if you have any ideas....



Another idea is to built a cupless headset. More on this later..

[Afsbz]

After I purchased a Bose A20 headset, my radio problems went away. Pricey, but I highly recommend.

[mike20sm]

A friend recently installed Dynamat in his work van to take out the noise of wobbly thin metal vibrating. It works great in cars, but it's too heavy for aircraft. I'm wondering however if a thin strip strategically placed like an inch wide strip diagonally would be light enough to not make a difference, yet enough to keep the loud noises down to a minimum. My friend realized that it didn't take all that much to have an effect. I'll try some tests when I get to that point.
[url]
http://www.dynamat.com/automotive-and-t ... at-xtreme/[/url]

[mike.smith]

A friend recently installed Dynamat in his work van to take out the noise of wobbly thin metal vibrating. It works great in cars, but it's too heavy for aircraft. I'm wondering however if a thin strip strategically placed like an inch wide strip diagonally would be light enough to not make a difference, yet enough to keep the loud noises down to a minimum. My friend realized that it didn't take all that much to have an effect. I'll try some tests when I get to that point.
[url]
http://www.dynamat.com/automotive-and-t ... at-xtreme/[/url]

I did that with some simple bent .025. Check out this and the next few posts:
http://www.mykitlog.com/users/display_l ... 181&row=11

At first I stuck them on with double sided carpet tape, but they fell off before I even got them out of my basement! I finally stuck them on with 3M VHB double sided tape. That stuff sticks like crazy!

Just adding one of these strips per bay helped a lot, compared to other Sonexes I've flown in without. I did not put any in the aft most bay, nor the baggage compartment bay, and I did not put them on the floor of the fuselage; only the sides.

[gammaxy]

As far as receiving I purchased a Headsets Inc. kit for my Chinese headset which replaces the speakers with 'real' electronic noise reduction units. When I turn this on the noise drops maybe 20db and I can actually understand everything on the radio. These are under $200 and work great. http://www.headsetsinc.com/ANR_kits.html

I've heard about this kit three times this week and currently have an email out to them checking if my cheap lightspeeds are compatible with their kit. I'm hoping they are.

[mike20sm]

I did that with some simple bent .025. Check out this and the next few posts:
http://www.mykitlog.com/users/display_l ... 181&row=11

Thanks for that idea It seems like it works well without adding much weight, and the tape has proven itself for a year now. I also dig the clear inspection plate, I'll have to remember that for later on when I get to building.

[pgerhardt]

Mike
the .025 bent stiffeners seem like a good idea. I know the sides vibrate and so does the floor. I had thought about gluing some old election signs to the panels to see if that worked.

A few DB less noise would be helpful in more than one way!

[Bryan Cotton]

Clever idea. I wonder what is the thinnest gauge angle that would provide benefit. Like the lexan covers too.

[DCASonex]

[quote="pgerhardt"]Mike
the .025 bent stiffeners seem like a good idea. I know the sides vibrate and so does the floor.

I have a number of these stiffener angles to help keep down oil-canning. With a bit of planning, these can do double duty and thus not just add weight. Have two full width of firewall integrated into battery box mounting, which also provides mounting for fuel flow sensor, and engine vent oil catch bottle. One on baggage compartment floor, (a small channel actually) forms base for cover over elevator push-pull tube, On floor behind that, integrated into ELT mount, Bottom rear hatch in next bay serves same function.

David A. Sonex TD, 3300

[mike.smith]

Being on this thread made me laugh Sunday! I went for a flight. 90 F OAT. On takeoff and climbout I was getting a lot of background noise in my headset! After I had just said I didn't get any! Turns out it was my full-open side vents. The air was blowing up my face and into the mic. As soon as I changed my climb angle the air was directed lower, avoiding the mic. Before I figured it out all I could think was, "you've got to be kidding!" Things that make you smile...