Mk2R Operation; Setting Audio Levels; Configuring Mk2R For Your Radios - microHAM MK2R Manual

For optimum operation of MK2R and MK2R+, the audio levels must be set properly. The function of each control
was described in the AUDIO MIXER and DVK sections of the manual.
About microphones and MK2R: In order to configure MK2R correctly, it is absolutely necessary to understand
the difference between electret and dynamic microphones.
A dynamic microphone consists of a small moving coil and a magnet. As sound moves the diaphragm,
the magnetic field in the coil changes producing a very small AC current which results in about 15
millivolts peak-to-peak at the of the typical transceiver. If a small voltage is applied to a dynamic
microphone, it requires more sound pressure to move the diaphragm and the output of the mic is
reduced. If the current through the coil is not limited, a dynamic mic can be damaged.
An electret mic consists of a capacitor with an electrostatically charged dielectric attached to the
diaphragm and a small amplifier. The voltage variation caused by sound on the electret capacitor is so
small that the amplifier is required before the output can be used. The amplifier requires a small DC
voltage ("bias") to operate and provides an audio signal of about about 500 millivolts peak to peak.
While dynamic and electret microphones each have their strong points, they are not directly
interchangeable. Where an electret mic will not work without a DC supply, a dynamic mic can be
damaged by that voltage. In addition, signal levels are very different with the typical electret mic
producing signal levels 20-60 times greater than that from a dynamic mic. Because of the differences,
one can not interchange dynamic and electret microphones without special consideration.
Most amateur transceivers are designed for use with dynamic microphones - this includes those made
by Elecraft, Kenwood, TenTec and Yaesu. On the other hand, Icom transceivers are designed for use
with electret microphones. When compared to other transceivers, Icom radios typically required a larger
audio input and have a DC voltage on their microphone line. Note: the Elecraft K3 can be configured for
either electret or dynamic microphones.

Configuring MK2R for your radios:

1. Open the top cover of MK2R and check position of the jumpers for the
three internal microphone preamps. The first preamplifier (RECORDING
– LIVE MIC) is used ONLY when the microphone is switched to the
sound card ("C" audio settings). The other two, (RADIO1 and one for
RADIO2) are used ONLY when the microphone is connected directly to
the radio ("A" audio settings).
2. RECORDING – LIVE MIC: This preamplifier is designed for use with
dynamic microphones including the Heil HC-4 or HC-5 elements. It
makes the relatively low output of the dynamic microphones compatible
with the mic input of most sound cards (including the USB Voice
CODEC in MK2R+). Jumpers for the Recording preamplifier are located
on the upper circuit board behind and slightly to the right of the Mix
control. This preamp is enabled at the factory.
3. RADIO1, RADIO2: These preamps allow using dynamic microphones (including the Heil HC4 and HC5
elements) with older Icom radios. The RADIO1 and RADIO2 preamplifier jumpers are located on the
right side of the upper circuit board behind the Recording/Digital controls. These preamplifiers are
bypassed at the factory.
WARNING: Never mix microphone types with MK2R. Use the same type of mic (electret or dynamic) at
both the front panel mic connection and the RJ-45 MIC jack.
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6 - MK2R OPERATION

Setting Audio Levels

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