FlexRadio 6400


The Flex6400

FLEX-6400 Software Defined Radio Transceiver:


Licence Required

Note: Licence Required
SmartSDR v2 requires a software license installed on the radio before it can be used with a FLEX-6000. All radios sold after May 19, 2017 All other radios require the purchase of a software license for the radio. Please see the section “Purchasing a SmartSDR Software License for your FLEX-6000” for instructions on how to purchase a license


Reference Documention

Directory Listing of Files for Download:

FLEX-6400 / FLEX-6600 HARDWARE REFERENCEVersion 2.1.3029 January 2018



Australian Distributor

Australian Distributor and Authorized Service Center is Future Systems (AUST.) Pty Ltd
3/40 Berriman Dr, Wangara WA, 6090
(08) 6336 9610


Front Panel Lights

Error Conditions:


Antenna Switching Matrix

The FLEX-6400 radios incorporate a unique smart antenna switching matrix to simplify connections from the radio to station antennas. ANT1 and ANT2 can be used for transceiver operation. The XVTR ports can be used for transverter operation or as an additional receive antenna port.
Atenna Switching Matrix.png



The transverter translates RF at one frequency to another for both transmit and receive. Generally, the transverters will have an RF side that is in the VHF or microwave region and an IF side in the HF or low VHF side. An example transverter block diagram is shown below:

This transverter converts from 10m RF signals (28MHz) to 1296MHz RF signals and back. The transverter shown in the picture has three RF connectors: RX IF - the 10m receive port TX IF - the 10m transmit port

RF - the RF input and output that goes to an antenna This type of transverter is known as a “Split IF” transverter since the IF side of the transverter utilizes both a receiver and a transmitter port. The other type of transverter is a “Common IF” transverter where a relay internal to the transverter is used to switch a single IF port between receive and transmit. Both the FLEX-6400 and FLEX-6600 are capable of either Common IF or Split IF operation.

Page 35 of 45 Copyright 2018 FlexRadio Systems. All Rights Reserved.FLEX-6400/FLEX-6600 Hardware Reference Manual https://www.flexradio.com/downloads/flex-6400-and-flex-6600-hardware-reference-manual-pdf/?wpdmdl=3104&refresh=5c9310c8c78ae1553141960

10.1 TRANSMIT POWER CONSIDERATIONS The default transverter output is 0 dBm (1.0 mW). The FLEX-6400/FLEX-6600 can produce an output on the XVTR port up to +15dBm for frequencies below 54MHz. If your transverter requires a higher-level input, it is recommended that you either modify the transverter for a lower power input or provide an amplifier to amplify the transmit signal before passing to the transverter. 10.2 RF CONNECTIONS - COMMON IF For a common IF configuration, the Common IF port of the transverter should be connected to the XVTR port on your FLEX-6400/FLEX-6600. This will be the only RF connection between the transverter and the radio. 10.3 RF CONNECTIONS - SPLIT IF For split IF transverters, the TX IF of your transverter should be connected to the XVTR port on the FLEX-6400/FLEX-6600. The RX IF port should be connected to either RX-A or RX-B (FLEX-6600 only). While it is technically feasible to use the ANT1 or ANT2 ports for receive, this is not recommended since these ports can produce high-power RF at any time that could damage your transverter. 10.4 PTT CONNECTIONS The radio will need to provide a PTT signal to place the transverter into transmit mode. Most transverters will have a grounded-PTT input. This should be connected to a FLEX- 6400/FLEX-6600 TX1, TX2 or TX3 output to cause the transverter to transmit. Depending on the design of the transverter, a weak pull-up may be required. 10.5 SEQUENCERS In some transverter applications, notably those that include a split RF output, preamplifiers and/or power amplifiers, a sequencer may be used. The specific details of connecting and configuring a sequencer are beyond the scope of this document, but the TX1, TX2 or TX3 output from the radio are generally used as an input to the sequencer to allow it to properly switch and enable/disable each component in your lash-up.


Digital Mode

There are two options for operating digital modes:

  1. Physical sound card connection
    1. preferred method
    2. does not use a physical sound card connection;
    3. uses DAX (Digital Audio eXchange) streamed digitally by Ethernet connection via the IP/UDP protocol.
    4. eliminates unnecessary analog to digital and digital to analog
      conversions which degrades signal to noise ratio (SNR) performance. The basic audio schematic is used to connect a FLEX-6400 to a PC sound card: • • PC Sound Card Mic / Line In <---> FLEX-6400/FLEX-6600 Audio Output PC Sound Card Line Out / Speaker Out <---> FLEX-6400/FLEX-6600 Audio Input FLEX-6400/FLEX-6600 Inputs: • • • Rear panel microphone connector [MIC] (1/8” TRS) Rear Balanced Input [BAL] (1/4” TRS connector) - FLEX-6600 only Rear Accessory input [ACC] (15-pin D-sub connector) FLEX-6400/FLEX-6600 Outputs: • • • Rear panel headphone [PHONES] connector (1/8” TRS connector) Rear Powered Speaker connector [PWR SPKR] (1/8” TRS connector) Rear Accessory output (15-pin D-sub connector)


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    DB25 Accessory Connector

    DB25 Accessory Connector
    The accessory connector is a high-density HD-15 female connector.
    1. Do not connect to VGA monitor.
    2. All Accessory inputs are 3.3VDC MAX Input


    Rear Panel Connectors




    Glenn Lyons VK4PK
    Ver:gnl20190330 - pre published v0.9