The Yaesu MD-100A8X Desktop Dynamic Microphone.

 
 
This Dynamic Microphone is designed for base station operation with the latest Yaesu HF transceivers, which in my case is the FT-450. It features selectable low-cut filtering and high-emphasis active filtering that  allows one to tailor the response for optimum voice clarity or DX punch.
The output Impedance is 500 Ohms.
The frequency response is 100Hz - 5KHz.
The Audio characteristic controls are:
LOW CUT Switch - OFF position: standard frequency response. [Shown in Green].
                                 Position 1: -3dB rolloff from 1000Hz to 150Hz. [Shown in Blue].
                                 Position 2: -3dB rolloff from 1000Hz to 300Hz. [Shown in Black].
HIGH EMPHASIS Switch on: +6dB @ 3000Hz. [Shown in RED]


One can understand what each Switch does clearly by looking at the Circuit diagram below.

Main Filter Switch SW01 (THRU position) bypasses all the internal audio filters.
When set to the FILT position, the filters are activated depending on the position of the Low Cut Switch, (SW03).
The Low Cut Switch has three functions: OFF, Position 1 and Position 2.
The OFF position provides a flat-audio characteristic transmitted audio.
Position 1 attenuates low tones for improved clarity in moderate band conditions, or if one has a naturally deep voice.
Position 2 attenuates low frequency tones more than position 1, for improved clarity in noisy band conditions.
The HIGH EMPHASIS filter switch (SW02) provides even crisper audio and is intended to be used when working CONTEST PILEUPS.
The Low Cut Switch is ignored when the HIGH EMPHASIS switch is ON and also when the Main Switch is set to the THRU position.

                             John has set the internal Audio Settings of his FT-450 Transceiver to:
                             DSP Microphone Equalizer to Flat (0) and Microphone Gain Level to NOR.
                           All filters are selected by the switches located on the base of the MD-100.

 
The base of the Microphone includes a large push-to talk switch and latching button.

Another feature is a Scanning Control, that allows one to TUNE the Transceiver upwards or downwards in frequency. This is an excellent feature as one doesn't have to turn the VFO knob manually on the Transceiver when checking a band with little activity. 

The Microphone Input Socket on the Yaesu FT-450 requires a Cable fitted with an JR-45 Plug; this is supplied with the MD-100A8X.

 
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G3NGD - May 2014.