JettPilot

My Feedback: (6)

I am having trouble finding a good, small line level microphone for the BWAV video transmitter. I am presently using a mic from supercircuits, its small, but its way to sensitive, even wrapped in plastic and tape it drives my audio to distortion [:@]. Anyone here know of a good mic that is the correct level for the 2.4 transmitters ?

JettPilot

Marro

I had the same problem. I got the high-gain mic from the supercircuits by mistake and the darn thing was so sensitive that was clipping the sound when the motor was on. I ended up cutting the shrink-wrapping, soldering a 1k trim pot ($1) in parallel to the mic and re-shrink wrapping the board. Now I have a variable gain mic that works great .

Hope this helps,

Miro

JettPilot

My Feedback: (6)

That sounds like a great fix, I will do it Where did you get the trim pot ??

JettPilot

Marro

Got mine at Fry's Electronics here in Bay Area, but I'm sure you can get it at local Radio Shack. Just make sure you mount it as close to the mic (as short wires as possible), or use shielded wire because of the high gain the wires will act as antennas.

Miro

typicalaimster

Super Circuits used to sell them. I don't see them listed on thier web site anymore. I'll see if I can dig up another source.

lvspark

I used this one with a 600mw lawmate module..
http://www.radioshack.com/product/in...entPage=search

steve_molmer

Jetttpilot:
The are many ways to help reduce the clipping.
The best way I have found to solve the problem of distortion in any omni-directional microphone element is to attenuate the frequency response.
All you need to do is to putt a 10k ohm pot is series with the output of the mic broad it self. adjust it till the clipping is removed. (with the engine running.)
Always mount the mic in the plane using foam and cover the mic cartridge with a wind cover to lower the back ground noise.
Never hard mount the mic with-out using foam around or on the mic mount.

I think you will find that you are over driving the amp on the transmitter and not the pre-amp on the mic board.
Let me know if this helps
cheers

JettPilot

My Feedback: (6)

Thanks, the microphone is wrapped in plastic and tape, and it so sensitive that it still overdrives even on the ground with the engine at idle [X(] I will try the resistor in series with the output, but I would like to use a fixed resistor. Given this, what value of resistor would you start with ?

Thanks,

JettPilot

Marro

Pardon my ignorance, but how does the reisistor in series on the output attenuates the freq. response??? If anything, it changes the impedence of the system to the point where the two are no longer in balance.

Miro

lvspark

Insertng a resistor in series with the audio signal will lower the voltage of the audio signal to the av/tx's audio in.
I have no idea what this will do to the impedence, but I have done things like this in the past and it seems to work good enough.

Chewing gum works pretty good too!

JettPilot

My Feedback: (6)

If I change the impedence, then the sound quality might not be perfect. And we all want to hear that gas engine and wind as if we were actually in the plane But given no other practical solution, I bought a bunch of resistors today and will find the one that brings the sound to a usable level.

JettPilot

Marro

I *think* I use about 500ohm (0.5k) in parallel to the mic. I could be off by 100ohm
Here's the video taken with this mic:

[link=http://video.google.com/videoplay?docid=4128587115946162367]video[/link]

Miro

JettPilot

My Feedback: (6)

Cool video, good sound, and lots of landing practice

JettPilot

Marro

Heh, thanks ! The plane was too small and way too heavy for the setup it was carying... I know, excuses, excuses I've just ordered an EasyStar that I can put all that stuff on, including pan/tilt camera.

Miro

steve_molmer

Jettpilot:
I have found that a 6.5 k ohm is a good starting place.