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MFJ-434B Instruction Manual Voice Keyer
13
keyer. The shield of the 8 conductor cable is connected to both the switch box chassis and voice
keyer chassis.
Do not connect the shield to the signal ground at either end, or erratic operation
may result.
STOP
MSG1
MSG2
MSG3
MSG4
MSG5
XMIT
GND (signal)
REMOTE BOX
IDC PLUG
Shield
NC
Computer Interface
The MFJ-434 selects memories through a buffered CMOS or TLL compatible interface. While
this interface is relatively immune to ground loops (it takes almost 3 V RMS ripple to cause
erratic control), it is still a good idea to use careful wiring techniques.
We recommend using the interface circuit shown below to protect the computer from external
RF. Each 2N3904 transistor should be driven into saturation for reliable control. This normally
requires at least 5 mA of base current.
Locate the driver transistors at the computer, and fully shield all circuitry. Be sure to ground the
emitters to the keyer's
signal ground
on the Voice-Keyer’ IDC plug only! Keep chassis ground
and signal ground separate, or erratic operation may result.
Содержание MFJ-434B
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