microHAM micro2R u2R User Manual page 28

From transceiver headphone outputs to the operator headphones.
micro2R allows flexible audio selection of from both radios Audio from the transceiver headphone jack is
connected to the micro2R headphone input, (optionally) passed through a switching relays which select the
audio source connected to each earphone and allow the user to select a variable level of mixing from one
ear to the other.
The audio connections can be defined for each transmit and receive state. The audio selection is indicated
by the RX Focus LEDs on the front panel.
The RX R1 (16) and RX R2 (17) buttons allow fast, manual selection of Radio1, Both (Split/Mix), or Radio 2
audio.
When the RADIO1 and RADIO2 buttons are pressed simultaneously
and held for more than .5 seconds, the AUTO light will illuminate and
micro2R will switch to the AUTO switching mode. The AUTO mode
recognizes six (6) states and STEREO "priority" state:
RADIO1=RX & RADIO2=RX & RX focus=R1
●
RADIO1=RX & RADIO2=RX & RX focus=R2
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RADIO1=COMPUTER TX & RADIO2=RX
●
RADIO1=RX & RADIO2=COMPUTER TX
●
RADIO1=MANUAL TX & RADIO2=RX
●
RADIO1=RX & RADIO2=MANUAL TX
●
STEREO - set by the logging software.
●
The "Stereo" state overrides all other states.
Receive audio (headphone) selections can be set using the "Headphones" panel on the Audio tab. The
audio source (Radio 1 Left/Right, Radio1 Left/Radio 2 Left, Radio 2 Left/Right) for each state is selected
using the radio buttons and becomes effective immediately.
NOTE: Separate switching for TX and Computer TX (Latch) is enabled/disabled using the front panel
LATCH button.
Headphone ground loop isolation.
Even when both radios are properly grounded it is possible to get a
hum in the headphones. This hum can be caused by differences in
headphone ground potential between the radios. micro2R keeps
the headphone ground of each radio isolated from the other as well
as from the u2R ground. However, when dual receive (stereo/split)
is selected the headphone grounds must be connected together.
To avoid the possibility of a ground loop in this situation micro2R
includes isolation transformers in line with each headphone channel
from radio2. These transformers are enabled by default but can be
bypassed by moving five jumpers as shown in the picture.
NOTE: While the Isolation transformers have excellent IMD
and saturation parameters, they also have up to 2dB loss. You may need to increase the
volume on radio2 to get the same level as when the headphones are connected directly to
the radio.
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