FLEX-6400/FLEX-6600 Hardware Reference Manual
Page
25 of 45
Copyright 2018 FlexRadio Systems. All Rights Reserved.
going to transmit. The TX Request Input can be enabled with a 3.3V to 5V logic signal
(when in Active High mode) or connecting to ground (when in Active Low mode). The
circuit is a 74LVC14 CMOS Schmidt trigger logic input with a 2.7k pullup to +3.3V. The IC
is 5V tolerant, so you can drive it with TTL levels as well. It can also be driven with an
open collector transistor or open drain MOSFET. Grounding the center pin of this
connector will prevent transmit from engaging (when in Active Low). Refer to the
SmartSDR documentation for information about how the interlock system works and how
to determine what is preventing transmit.
The SmartSDR for Windows Software User’s
Guide also includes details on how to interlock two radios from simultaneous transmit for
a Multi/2 operation.
7.9
EXTERNAL AMPLIFIER ALC INPUT
This RCA connector is provided to receive an ALC signal from an external amplifier. The
shell is ground, and the pin is a negative going DC voltage, zero to -4 Volts.
!
–
VOLTAGES BELOW -4VDC MAY DAMAGE THE ALC INPUT.
Δ –
Please note this input is provided as a safety measure for external amplifiers. It is
NOT meant to be used in regular operation as an active power control input or to
modify the “attack” of an external amplifier. Almost all modern HF amplifier
manufacturers discourage the use of ALC in normal operation. In fact, many amplifiers
do not have ALC implemented. The
SmartSDR Software User’s Guide
describes the
recommended method for setting the power level on an external amplifier on a per-
band basis.
7.10
REMOTE POWER ON INPUT
This RCA connector is provided for remote power-on functionality. When the Remote
Power ON feature is enabled, shorting this input to ground will activate the radio -
opening this connector will disable power on the radio. Refer to the SmartSDR
documentation for information on how to configure this input. (Note: 3.3VDC Max Input.)
7.11
GPS ANTENNA INPUT (W/GPSDO OPTION)
If the radio is equipped with the optional GPSDO, this female SMA connector is for
connecting the included GPS antenna. The GPSDO provides DC bias for the antenna
preamp. It can work with antennas that require either 3.3 Volt or 5 Volt DC bias.
7.12
10MHZ REFERENCE OUTPUT (W/GPSDO OPTION)
If the radio has the optional GPSDO, the 10 MHz reference output is a buffered 3.3V p-p
output of the 10 MHz oscillator in the GPSDO. The signal can be used to provide a
reference signal for external equipment. The connector is a female SMA.