General aviation headset testing for ham radio скачать в хорошем качестве

General aviation headset testing for ham radio

This video shows a further step towards getting an aircraft headset with boom mic to work with a ham radio rig. The benefits of these headsets are the strong fit over the ears that provides a very quiet listening environment, rated at -24dB passive noise reducing design. Aircraft cockpits are noisy and loud, so the mono headphones need to be well-fitting to the pilot, including glasses! The mics are 'carbon-equivalent' electret/dynamic mics that are intentionally 'deaf' to sounds other than in close proximity to the mic. For ham radio rigs, these can pose a problem: the aviation standard is 400 mV output into roughly 500 Ohm loads. In an earlier video, I experimented with my Elecraft MH3 PTT mic with elecret microphone with 3v DC bias. The output appears small - less than 10mV , and needs a simple one-transistor pre-amp to show a signal on my oscilloscope. That tells me that I need to attenuate the aviation mic to a similar level. In this video clip, I make use of John Raydo's K0IZ circuit to match impedance and attenuation to the 20-40mV range for the mic. The true test will be to plug this circuit into the rig and see if the rig pre-amp can create a usable and clear audio on VOX and try a QSO and get an audio report back! Watch this space.