MFJ-1708SDR Instruction Manual Transmit/Receive Switch
2
INTRODUCTION
Software Defined Radios are becoming commonplace, and often have to work
in conjunction with radio transceivers. Some means of protecting the SDR
input is required while the rig is transmitting. Not all radios have an RF out
(protected) jack, and those that do often require some sort of loopback
connection to completethe receive audio path. Radios with IF outputs do not
allow the full spectrum to be monitored. Some means of antenna sharing is often
required which will isolate the SDR during transmit operations. The MFJ-
1708SDR Transmit/Receive Switch will solve this.
TECHNICAL DESCRIPTION
The MFJ-1708SDR T/R switch uses a relay, which switches from transmit to
receive mode. When no power is applied to the unit, it is in the transmit mode.
Once power is applied the relay switches on and the unit is in receive mode.
When the unit senses RF or the control line is grounded from a keyer or PTT
switch, it switches the relay off and the unit is in transmit mode.
The delay adjustment allows you to change how fast the relay switches back to
the receive mode. It is adjustable from 0 to 2 seconds.
The MFJ-1708SDR T/R Switch requires 12 VDC or 110 VAC with MFJ-1312D
power supply.
CONTROLS
Power……………2.1mm Coaxial power input jack with center pin positive and
shield negative
PTT….…………..RCA input jack
Delay…………….Controls time delay for switching
Radio….…………SO-239 Coaxial connector
Antenna………….SO-239 Coaxial connector
SDR….…………..SO-239 Coaxial connector