I am considering to capture more in-flight videos. 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. 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. 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.
So yesterday I hit the Internet to find the solution. Thank you www.epanorama.net. It turned out that I needed a simple attenuator to bring the audio level down with -40 dB. A resistor voltage divider would do the job. In order to shield the possible DC voltage on the microphone input, you also need a capacitor to block any DC going back to your aircraft's intercom. And Frank told me to add some high cut-out capacitors to remove high frequency noise. A new simple electronics project was born. Nothing active, nothing complicated, no batteries, no transistors ... everything back to basics: soldering, connectors, cables, turning knob, housing. Fun !
Total cost: neglectable in view of the cost of a flying hour. Time: well spent. Nerd factor: high. Proudness: even higher ;-)
I tested my little project at home - with success. And now I found a new excuse to go to the aircraft nearest to my house to test it there ... I would be happy to help anyone with similar questions, just mail.
I tested my Attenuator in an aircraft and it works well. Here 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.
Here is the Attenuator Test Audio (MP3).
In the meanwhile I further improved my design a little so I now have a " Attenuator+ ".
The way it works is: you plug the Attenuator+ into the headphone output of the intercom system, and your headphone jack itself plug into an extra plug into the Attenuator+. It's a basic loop through of the audio, so your headset keeps its normal function. A long output cable then plug directly into the microphone input of your camcorder / audio recorder. You can set the attenuation with a turning knob. It's best to test this before the flight by means of checking how the audio comes through and get recorded on your recording device.
If you are interested, I can make one and sell it to you ... just let me know !
