Balanced Armature Design Eh-3 Military Headset Microphone For Crystal Radio
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Balanced Armature Design Eh-3 Military Headset Microphone For Crystal Radio:
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Up for sale is a NOS vintage Chinese Military Balanced Armature Headphone and microphone. These communications headset microphone were manufactured around 1970, design for the first Chinese Military 15 watt semiconductor transceiver. This EH-3 headset microphone is a collectable item and will be a welcome addition to your collection. Perfect for ham transceiver, very good for coping cw signals or crystal radio listening.
Although it is low impedance (150Ω DC resistance, about 600Ω ~ 1000 Ω impedance), it is extremely sensitive. As a balanced armature device, it is sensitive enough to be classed as “sound-powered”, i.e.: if connected to a similar pair of headset, voice communication is possible without the need for a battery.
If connect this headphone via a suitable high-low impedance matching transformer (such as a Bogen 7254 watt audio matching transformer or Mouser Electronics 42TM117-RC 50K:1K audio transformer) or directly connected the detector to the appropriate tap point on the tuning coil, this headphone would be ideally suited for crystal radio reception. I have tested it in my crystal radio and it sounds very loud, the sensitivity of this balanced armature headphone is much better than a good high impedance (DC resistance 2000 or 4000Ω) headphone.
Its microphone has
two 580Ω magnetism elements in series and is installed back to back, this is a
noise cancellation design. When noise goes into both side of the microphone, the
diaphragm will not vibrate too much because the energy from both side are counteract. But
when a operator talk close at one side of the microphone, the diaphragm will vibrate
and produce electric current in the coils.
The microphone sounds fairly loud as a receiver when connect it to a crystal radio output.
The cable from headset to microphone is about 2-1/2 foot long, from microphone to the 7 pins military type connector is about 3-1/2 foot long. The headphone is connects to pin #3 and pin #5 in the connector with microphone push button OFF ( the headphone is always on if connects to pin #1 and pin #5 in the connector ). The microphone is connects to pin #2 and pin #4 in the connector with that push button ON.
The quality of construction for this headset is great because it was designed for military application. The balanced armature elements are sealed and very difficult to open (the inside view pictures of the headphone element were taken from same type of headset)
Please E-mail any questions you may have before you offer. It is
time to clean up the electronic related items in my garage, please keep an eye
out for my other sales! Thanks for looking!
make payment arrangements within 3 days. I accept PayPal. International payment
must be by PayPal only, in US dollars. Payment is expected within 10 days of
sale closing, or item will be released for sale. International buyer pays
$23.95 shipping charge for US Postal Service Priority Mail.