I was considering to capture more in-flight videos of my private flying hobby. I have a vintage Sony DCR PC9E camcorder, standard definition, but perfect for the job. Almost all the videos in this website have been captured with this venerable piece of equipment.
But I know that I have to do a better job with capturing the audio. I wanted to record ATC audio and intercom audio in-flight with a camcorder or audio recorder. Just capturing the audio with the built-in microphone of any consumer camcorder or audio recorder gives you nothing but engine noise and no intercom or ATC voices. Alternatively when you connect the intercom audio from a free headphone plug directly to the microphone input of the camcorder, the recorded audio is distorted due to the too high levels coming from the intercom. Also I didn't want to fiddle with sticking microphone inside my headset.
So I hit the internet to find the solution but didn't find a product. So I decided to design it myself ! It turned out that I needed an attenuator to bring the audio level down with -40 dB. A new electronics project was born. Nothing active, no batteries, no transistors ... everything back to basics: soldering, connectors, cables, turning knob, housing but in a secure tight package. Fun !
I tested the project at home - with success. And then I found a new excuse to go flying an aircraft to test it for real. Total cost: neglectable in view of the cost of a flying hour. Time: well spent. Nerd factor: high. Proudness: even higher ;-)
I tested my Attenuator in a typical GA aircraft and it works very well. Below you can hear a piece of the test that I performed and recorded with my camcorder. When the controller in Kortrijk reads the new clearance of the arriving twin so he can continue IFR to Merville, I turn down the attenuation (at around "squawk 6070"). You can hear the mike input on the camcorder saturate and the audio deforms. Later in this recording I crank up the attenuation again and the deformation disappears. That proves the working of the attenuator: the saturation and deformation disappear when the attenuation is set.
=> Here is the Attenuator Test Audio (MP3).
Frank & self also tested his attenuator on our flight trip in Vegas. You can hear the attenuator in action in de videos here:
Also check out the Attenuator+ in use during training flights by my customer Chris: http://vimeo.com/18917000 and http://vimeo.com/19430838.
In the meanwhile I further refined my design a little with additional filters to improve the sound so I now have a "Attenuator+". I also added a isolation switch to cater for fast disconnection of the camcorder.
The way it works is: you plug the large male Attenuator+ jack into a female headphone output of the intercom system, and your large male headphone jack plugs into an extra female connector into the Attenuator+. It's a basic mono loop-through of the audio, so your headset keeps its normal function. A long output cable from the Attenuator+ then plugs directly into the small female jack microphone input of your camcorder / audio recorder. You can set the attenuation with a turning knob. The whole system can be isolated from your intercom with the flip of a switch for safety reasons (yes, this is a good design ;-) !). It's best to test and set this before the flight by means of checking how the audio comes through and get recorded on your recording device. It works with my old Sony camcorder, and it should work with any recording device which has a small female microphone input jack.
I have already delivered Attenuators+ to Florida, Belgium and Holland ... and the users are happily capturing in-flight intercom and ATC... in full safety and without the engine noise or distortion.
If you are interested to record your own in-flight ATC and intercom audio with my Attenuator+, just let me know ! I have made a couple extra and I am in interested in selling them. I also documented more details in a manual. I can send a copy to you so you can verify if the Attenuator+ will work.
The Attenuator+ is an amateur hobby project. It has not been officially tested, validated or approved by any authority in this field. The designer disclaims all direct or indirect liabilities. It to be used only on the user's risk in private, non-commercial, non-professional settings.
