FlexRadio Systems FLEX-6400 Quick user guide

Copyright 2018 FlexRadio Systems. All Rights Reserved. FlexRadio Systems is a registered trademark and SmartSDR is a
trademark of FlexRadio Systems. All other brands or names are trademarks of their respective owners.
FLEX-6400 / FLEX-6600 HARDWARE REFERENCE
Version 2.1.30
29 January 2018

FLEX-6400/FLEX-6600 Hardware Reference Manual
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Copyright 2018 FlexRadio Systems. All Rights Reserved.
TABLE OF CONTENTS
1INTRODUCTION.................................................................................................................... 5
1.1 Welcome................................................................................................................... 5
1.2 Manual Layout.......................................................................................................... 5
1.3 Notices to the User................................................................................................... 6
2WARRANTY INFORMATION............................................................................................. 7
3IMPORTANT NOTICE –READ BEFORE OPERATING THIS UNIT .......................... 8
3.1 Precautions............................................................................................................... 8
3.2 Legal Notices ............................................................................................................ 9
3.3 Copyright Information........................................................................................... 11
4SPECIFICATIONS................................................................................................................ 13
4.1 General.................................................................................................................... 13
4.2 Transmitter ............................................................................................................ 13
4.3 Receiver.................................................................................................................. 14
5UNPACKING AND INSPECTATION................................................................................ 15
5.1 Unboxing................................................................................................................. 15
5.2 Visual Inspection.................................................................................................... 15
5.2.1 General .............................................................................................................. 15
5.2.2 Radio.................................................................................................................. 15
5.2.3 Included Accessories........................................................................................ 15
5.2.4 Additional Items Not Included but Required................................................. 16
5.3 Reporting Damage ................................................................................................. 16
6FRONT PANEL CONTROLS AND CONNECTIONS ..................................................... 17
7REAR PANEL CONNECTIONS......................................................................................... 19
7.1 DC Power Input....................................................................................................... 19
7.1.1 Fused Internally at 30 Amps ........................................................................... 20
7.2 Transceiver Antenna Ports [1,2] .......................................................................... 20
7.3 Powered Speakers ................................................................................................. 21
7.4 CW Key/Paddle Jack.............................................................................................. 21
7.5 Balanced Audio Input (FLEX-6600 only)............................................................. 22
7.5.1 MIC vs. LINE Use............................................................................................... 22
7.5.2 Line Level .......................................................................................................... 22
7.6 Accessory Connector ............................................................................................. 23
7.6.1 Pin 1: Line In..................................................................................................... 23
7.6.2 Pin 2: Line1 Out ................................................................................................ 23

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7.6.3 Pin 3: Line2 Out ................................................................................................ 23
7.6.4 Pin 4: KEY In ..................................................................................................... 23
7.6.5 Pin 5, Pin 6, Pin 7, Pin 8 and Pin 10: GROUND............................................... 24
7.6.6 Pin 9: +5VDC ..................................................................................................... 24
7.6.7 Pin 11: Accessory TX........................................................................................ 24
7.6.8 Pin 12: SDA I/O................................................................................................. 24
7.6.9 Pin 13: Accessory TX REQ................................................................................ 24
7.6.10 Pin 14: PTT in ................................................................................................... 24
7.6.11 Pin 15: SCL I/O.................................................................................................. 24
7.7 PTT Input................................................................................................................ 24
7.8 TX Request Input (interlock)................................................................................ 24
7.9 External Amplifier ALC Input ............................................................................... 25
7.10 Remote Power On Input........................................................................................ 25
7.11 GPS Antenna Input (w/GPSDO option)................................................................ 25
7.12 10MHz Reference Output (w/GPSDO option)..................................................... 25
7.13 Ethernet Connector ............................................................................................... 26
7.14 USB 2.0 Ports.......................................................................................................... 26
7.15 External Display...................................................................................................... 26
7.16 10 MHz Input .......................................................................................................... 26
7.16.1 Radio Oscillator Startup................................................................................... 26
7.17 TX Relay Outputs [1,2,3] ....................................................................................... 26
7.18 RX-B RF Input (FLEX-6600 only) ......................................................................... 27
7.19 XVTR-B Transverter Port (FLEX-6600 only)....................................................... 27
7.20 Microphone Jack .................................................................................................... 27
7.21 XVTR-A Transverter Port...................................................................................... 28
7.22 RX in/RX-A RF Input.............................................................................................. 28
7.23 Headphone Jack ..................................................................................................... 28
7.24 Chassis Ground ...................................................................................................... 28
8INSTALLATION................................................................................................................... 30
8.1 Safety ...................................................................................................................... 30
8.2 Radio Placement .................................................................................................... 30
8.3 Environmental Considerations............................................................................. 30
8.4 Connecting to a PC ................................................................................................. 30
8.4.1 Ethernet Cabling Requirements...................................................................... 30
8.4.2 Direct PC Connection (Link-Local) ................................................................. 31
8.4.3 Connecting via a Local Network...................................................................... 31
8.4.4 Installing SmartSDR ......................................................................................... 32

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9FHM-X MICROPHONES..................................................................................................... 33
9.1 FHM-2 Specifications ............................................................................................. 33
9.2 Connecting the FHM-2 Microphone....................................................................... 33
9.3 Best Practices .......................................................................................................... 33
10 TRANSVERTER SETUP...................................................................................................... 35
10.1 Transmit Power Considerations .............................................................................. 36
10.2 RF Connections - Common IF ................................................................................ 36
10.3 RF Connections - Split IF........................................................................................ 36
10.4 PTT Connections..................................................................................................... 36
10.5 Sequencers............................................................................................................... 36
10.6 Multiple Transverters.............................................................................................. 36
11 DIGITAL MODE SETUP (SOUND CARD INTERFACE).............................................. 37
12 ANTENNA CONSIDERATIONS ........................................................................................ 39
12.1 Antenna Selection.................................................................................................. 39
13 ANTENNA TUNER UNIT (ATU)........................................................................................ 41
13.1 Specifications .......................................................................................................... 41
14 OPTIONAL GPS DISCIPLINED OSCILLATOR (GPSDO) SETUP ............................. 42
14.1 GPSDO Introduction .............................................................................................. 42
14.2 GPS Antenna Placement ........................................................................................ 42
14.3 GPSDO Lock Sequence and Status Indicators...................................................... 42
15 CALIBRATION..................................................................................................................... 44
15.1 Frequency Calibration............................................................................................. 44
16 KEY CONTACTS.................................................................................................................. 45
16.1 Headquarters / USA ................................................................................................ 45
16.2 Outside of the USA ................................................................................................. 45

FLEX-6400/FLEX-6600 Hardware Reference Manual
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Copyright 2018 FlexRadio Systems. All Rights Reserved.
1INTRODUCTION
1.1 WELCOME
Thank you for purchasing the FLEX-6400/FLEX-6600 direct sampling software defined
radio (SDR) from FlexRadio Systems. The FLEX-6400 and FLEX-6600 are top performing
HF/6m transceivers that make use of the latest SDR technology using direct digital
sampling at the RF input for exceptional performance and distortion free reception.
Direct sampling technology eliminates analog mixing and amplification to minimize
spurious output and in-band intermodulation distortion to ensure ultra-clean RF
transmission.
The FLEX-6400 and FLEX-6600 along with the SmartSDR software “ecosystem” represents
the ultimate operating experience for amateur radio operators.
1.2 MANUAL LAYOUT
The FLEX-6400/FLEX-6600 Hardware Reference Manual is designed as a guide for use
while installing, configuring, and integrating your FLEX-6400/FLEX-6600 into your amateur
radio station. This manual expands on the FLEX-6400/FLEX-6600 Quick Start Guide
regarding connection details and hardware configuration including basic connectivity
information for interfacing with the more common types of third-party hardware. It is
designed for use in conjunction with the SmartSDR Software User’s Guide. References to
the SmartSDR Software User’s Guide will be provided to assist you.
Throughout this manual, important references will be highlighted for your information
and safety. The following symbols and styles will be used:
! –WARNING: THIS MEANS THAT THERE IS A POTENTIAL SAFETY HAZARD IF THE RADIO
IS CONFIGURED OR OPERATED IMPROPERLY. PAY SPECIAL ATTENTION TO ALL “!”
WARNINGS.
Δ –CAUTION: This is a precautionary statement to acknowledge there is a risk to
damaging your radio or operating it in an unintended manner. Pay special attention to
the “Δ” symbol to get the most from your FLEX-6400/FLEX-6600.
I –Information: Important information will be highlighted with the “i” symbol. Read
these notes for helpful hints and details about your FLEX-6400/FLEX-6600.

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1.3 NOTICES TO THE USER
IMPORTANT NOTICE - READ BEFORE OPERATING THIS UNIT
WARNING!
This radio has been configured to operate in your country according to your nation's
regulations. It will operate on frequencies which are not allowed for public use. You are
required to have a valid amateur radio license of an appropriate class from your
government to have the privileges to operate on amateur radio frequencies.
Except those actions which have been described in the FLEX-6400/FLEX-6600 Quick Start
Guide, FLEX-6400/FLEX-6600 Hardware Reference Manual, and SmartSDR Software
User’s Guide, no other manipulations to the radio are allowed. The unit must only be
opened and/or serviced by a qualified technician. Unauthorized repairs may damage the
radio and void the manufacturer’s warranty.
Please study the FLEX-6400/FLEX-6600 Quick Start Guide and the FLEX-6400/FLEX-6600
Hardware Reference Manual and SmartSDR Software User’s Guide prior to operating the
unit. These documents contain important information for safe operation.
For any questions due to misunderstanding, translation errors and alike, please refer to
the FLEX-6400/FLEX-6600 Hardware Reference Manual and SmartSDR Software User’s
Guide first.
Radio frequency energy (RF) from transmitters can interact with some electronic devices,
such as cardiac pacemakers and defibrillators. Please refer to the implanted pacemaker
or defibrillator manufacturer's instructions with respect to precautions to be taken in the
vicinity of an amateur radio transmitter. If any interaction or interference with a
pacemaker or implanted defibrillator is suspected, STOP transmitting immediately.

FLEX-6400/FLEX-6600 Hardware Reference Manual
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Copyright 2018 FlexRadio Systems. All Rights Reserved.
2WARRANTY INFORMATION
FLEX-6400 / FLEX-6600 Signature Series 2-Year Limited Hardware Warranty
This Limited Warranty is effective as of the date of first purchase by the consumer.
Original equipment hardware warranties and manufacturer support for FlexRadio
Systems products applies only to the original purchaser and are not transferable unless a
Warranty Transfer agreement is purchased from FlexRadio Systems. Before sending in
your product for service, it is recommended that you query the FlexRadio Community to
make sure your issue is not easily resolved. If you still have an issue, submit a request for
support via the FlexRadio HelpDesk. Once you are assigned an incident or ticket number,
one of our Technical Support Engineers will determine if the issue your product is
experiencing requires service or repair and will either issue you an RMA (Return Material
Authorization) number for service in Austin, TX or refer you to another authorized Service
Center. Any product returned for service that is out of warranty or has had its warranty
voided is subject to a one (1) hour diagnostic bench charge. This charge will be applied to
any work performed.
What is Covered:
During the first thirty (30) days after the date of shipment, FlexRadio Systems will fully
repair or replace a defective product at their discretion. For the remaining two (2) years
after the date of shipment, FlexRadio Systems will replace defective parts free of charge
(post-paid) for transceiver components only. Any replacement hardware parts will be
warranted for the remainder of the original warranty period or ninety (90) calendar days
from the date of installation or repair, whichever is longer. FlexRadio Systems will also
correct any failure caused by defective parts and materials. You must send the unit at
your expense to FlexRadio Systems. FlexRadio Systems will pay return shipping to the
country of purchase.
What is Not Covered:
This Limited Warranty as it pertains to the transceiver or radio components does not
cover repair or damage caused by (1) misuse, negligence or user modifications; (2) any
performance or operational malfunctions involving non-FlexRadio Systems accessory
equipment; (3) connection to improper or unstable voltage supply; (4) improper
execution of hardware calibration or test routines; (5) the incorrect installation of any and
all cables connected to the radio by the user; (6) the use of third-party software
applications or hardware that directly or indirectly controls radio functions and/or
operating state by utilizing a communication or control protocol, such as, but not limited
to CAT or I2C commands or (7) random acts of nature such as flood, fire, water, weather
related storm, lightning or electrostatic discharge damage.

FLEX-6400/FLEX-6600 Hardware Reference Manual
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Copyright 2018 FlexRadio Systems. All Rights Reserved.
Limitation of Incidental or Consequential Damages:
This warranty does not extend to non-FlexRadio Systems equipment or components used
in conjunction with our products. Any such repair or replacement is the responsibility of
the customer. FlexRadio Systems shall not be liable or responsible for reimbursement for
any special, indirect, incidental or consequential damages, including but not limited to
any loss of business or profits, loss of property, loss of revenue, loss of use, loss of data,
inconvenience or cost of unauthorized service.
3IMPORTANT NOTICE –READ BEFORE OPERATING THIS UNIT
3.1 PRECAUTIONS
! –THIS UNIT IS NOT A TOY. IT MUST NOT BE HANDLED BY CHILDREN NOR
PLACED/OPERATED WITHIN REACH OF CHILDREN.
! –DO NOT LEAVE PACKING MATERIAL FOR THIS UNIT UNATTENDED. IT MAY BE
HARMFUL TO CHILDREN IF MISUSED.
! –THIS UNIT CONTAINS SMALL PARTS THAT COULD BE A CHOKING HAZARD TO SMALL
CHILDREN. DO NOT LEAVE ACCESSORIES UNATTENDED.
! –DO NOT OPERATE THIS UNIT IN POTENTIALLY EXPLOSIVE ENVIRONMENTS.
! –NEVER ATTEMPT TO INSERT WIRES OR ANY TOOLS INTO THE INTERIOR OF THIS UNIT
DURING OPERATION. THIS MAY CAUSE FIRE OR ELECTRIC SHOCK.
! –THIS UNIT MUST ONLY BE OPERATED WITH THE ELECTRICAL POWER DESCRIBED IN
THE FLEX-6400/FLEX-6600 QUICK START GUIDE. NEVER CONNECT THE +13.8VDC
POWER CONNECTOR DIRECTLY TO AN AC OUTLET. THIS MAY CAUSE A FIRE, INJURY, OR
ELECTRICAL SHOCK.
! –NEVER CONNECT OR DISCONNECT ANTENNAS WHILE IN TRANSMIT MODE. THIS
MAY CAUSE ELECTRICAL SHOCK OR RF BURNS TO YOUR SKIN AND DAMAGE TO THE
UNIT.
! –THIS UNIT GENERATES RADIO FREQUENCY (RF) ENERGY. USE CAUTION AND
OBSERVE PROPER SAFETY PRACTICES REGARDING YOUR SYSTEM CONFIGURATION.
WHEN ATTACHED TO AN ANTENNA, THIS RADIO IS CAPABLE OF GENERATING RF
ELECTROMAGNETIC FIELDS WHICH REQUIRE EVALUATION ACCORDING TO YOUR
NATIONAL LAW TO PROVIDE ANY NECESSARY ISOLATION OR PROTECTION REQUIRED,
WITH RESPECT TO HUMAN EXPOSURE!
Δ - This unit must only be opened and/or serviced by a qualified technician. Opening
the unit may void the manufacturer’s warranty
Δ - Do not operate this unit in areas of extreme humidity.
Δ - Avoid operating this radio in direct sunlight or other areas of extreme heat,
excessive vibration, or mechanical force.
Δ - When using earphones, use caution when adjusting the volume to prevent any harm
to your hearing.

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Copyright 2018 FlexRadio Systems. All Rights Reserved.
Δ - If this unit is intended for use in commercial applications, special safety regulations
and cautions may apply to prevent accidents.
Δ - If any defect, abnormal result, or other observations occur that are not covered by
the Quick Start Guide; immediately cease operation and contact the manufacturer or
local distributor for operational advice or repair of the unit.
I- No other physical modification of this radio is allowed. Any other use or modification
(including software changes that affect operational characteristics) will void the
manufacturer’s warranty.
I- Ensure proper ventilation around the radio; this includes 2” clearance on the sides and
back.
I- If you operate this unit in conjunction with a linear amplifier, always make sure your
output power is below the maximum input limits of the amplifier. Consult your
amplifier owner’s manual for proper connection and operation.
3.2 LEGAL NOTICES
©2013-2018 FlexRadio Systems. All rights reserved. FlexRadio Systems®, FLEX-6000™
SmartSDR™, SmartLink™ and related trademarks, names, and logos are the property of
FlexRadio Systems and are registered and/or used in the U.S. and countries around the
world.
All other trademarks are the property of their respective owners.
This documentation including all documentation incorporated by reference herein such as
documentation provided or made available at support.flexradio.com/downloads is
provided or made accessible "AS IS" and "AS AVAILABLE" and without condition,
endorsement, guarantee, representation, or warranty of any kind by FlexRadio Systems
and FlexRadio assumes no responsibility for any typographical, technical, or other
inaccuracies, errors, or omissions in this documentation. In order to protect FlexRadio
proprietary and confidential information and/or trade secrets, this documentation may
describe some aspects of FlexRadio technology in generalized terms. FlexRadio reserves
the right to periodically change information that is contained in this documentation;
however, FlexRadio makes no commitment to provide any such changes, updates,
enhancements, or other additions to this documentation to you in a timely manner or at
all.
This documentation might contain references to third-party sources of information,
hardware or software, products or services including components and content such as
content protected by copyright and/or third-party web sites (collectively the "Third Party
Products and Services"). FlexRadio does not control, and is not responsible for, any Third-
Party Products and Services including, without limitation the content, accuracy, copyright
compliance, compatibility, performance, trustworthiness, legality, decency, links, or any
other aspect of Third Party Products and Services. The inclusion of a reference to Third

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Copyright 2018 FlexRadio Systems. All Rights Reserved.
Party Products and Services in this documentation does not imply endorsement by
FlexRadio Systems of the Third-Party Products and Services or the third party in any way.
EXCEPT TO THE EXTENT SPECIFICALLY PROHIBITED BY APPLICABLE LAW IN YOUR
JURISDICTION, ALL CONDITIONS, ENDORSEMENTS, GUARANTEES, REPRESENTATIONS,
OR WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING WITHOUT
LIMITATION, ANY CONDITIONS, ENDORSEMENTS, GUARANTEES, REPRESENTATIONS OR
WARRANTIES OF DURABILITY, FITNESS FOR A PARTICULAR PURPOSE OR USE,
MERCHANTABILITY, MERCHANTABLE QUALITY, NON-INFRINGEMENT, SATISFACTORY
QUALITY, OR TITLE, OR ARISING FROM A STATUTE OR CUSTOM OR A COURSE OF
DEALING OR USAGE OF TRADE, OR RELATED TO THE DOCUMENTATION OR ITS USE, OR
PERFORMANCE OR NON-PERFORMANCE OF ANY SOFTWARE, HARDWARE, SERVICE, OR
ANY THIRD PARTY PRODUCTS AND SERVICES REFERENCED HEREIN, ARE HEREBY
EXCLUDED. YOU MAY ALSO HAVE OTHER RIGHTS THAT VARY BY STATE OR PROVINCE.
SOME JURISDICTIONS MAY NOT ALLOW THE EXCLUSION OR LIMITATION OF IMPLIED
WARRANTIES AND CONDITIONS. TO THE EXTENT PERMITTED BY LAW, ANY IMPLIED
WARRANTIES OR CONDITIONS RELATING TO THE DOCUMENTATION TO THE EXTENT
THEY CANNOT BE EXCLUDED AS SET OUT ABOVE, BUT CAN BE LIMITED, ARE HEREBY
LIMITED TO NINETY (90) DAYS FROM THE DATE YOU FIRST ACQUIRED THE
DOCUMENTATION OR THE ITEM THAT IS THE SUBJECT OF THE CLAIM.
TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW IN YOUR JURISDICTION, IN
NO EVENT SHALL FLEXRADIO SYSTEMS BE LIABLE FOR ANY TYPE OF DAMAGES RELATED
TO THIS DOCUMENTATION OR ITS USE, OR PERFORMANCE OR NON-PERFORMANCE OF
ANY SOFTWARE, HARDWARE, SERVICE, OR ANY THIRD PARTY PRODUCTS AND SERVICES
REFERENCED HEREIN INCLUDING WITHOUT LIMITATION ANY OF THE FOLLOWING
DAMAGES: DIRECT, CONSEQUENTIAL, EXEMPLARY, INCIDENTAL, INDIRECT, SPECIAL,
PUNITIVE, OR AGGRAVATED DAMAGES, DAMAGES FOR LOSS OF PROFITS OR
REVENUES, FAILURE TO REALIZE ANY EXPECTED SAVINGS, BUSINESS INTERRUPTION,
LOSS OF BUSINESS INFORMATION, LOSS OF BUSINESS OPPORTUNITY, OR CORRUPTION
OR LOSS OF DATA, FAILURES TO TRANSMIT OR RECEIVE ANY DATA, PROBLEMS
ASSOCIATED WITH ANY APPLICATIONS USED IN CONJUNCTION WITH FLEXRADIO
SYSTEMS PRODUCTS OR SERVICES, DOWNTIME COSTS, LOSS OF THE USE OF FLEXRADIO
PRODUCTS OR SERVICES OR ANY PORTION THEREOF OR OF ANY COST OF SUBSTITUTE
GOODS, COSTS OF COVER, FACILITIES OR SERVICES, COST OF CAPITAL, OR OTHER
SIMILAR PECUNIARY LOSSES, WHETHER OR NOT SUCH DAMAGES WERE FORESEEN OR
UNFORESEEN, AND EVEN IF FLEXRADIO HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGES.
TO THE MAXIMUM EXTENT PERMITTED BY APPLICABLE LAW IN YOUR JURISDICTION,
FLEXRADIO SYSTEMS SHALL HAVE NO OTHER OBLIGATION, DUTY, OR LIABILITY
WHATSOEVER IN CONTRACT, TORT, OR OTHERWISE TO YOU INCLUDING ANY LIABILITY
FOR NEGLIGENCE OR STRICT LIABILITY.

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Copyright 2018 FlexRadio Systems. All Rights Reserved.
THE LIMITATIONS, EXCLUSIONS, AND DISCLAIMERS HEREIN SHALL APPLY: (A)
IRRESPECTIVE OF THE NATURE OF THE CAUSE OF ACTION, DEMAND, OR ACTION BY YOU
INCLUDING BUT NOT LIMITED TO BREACH OF CONTRACT, NEGLIGENCE, TORT, STRICT
LIABILITY OR ANY OTHER LEGAL THEORY AND SHALL SURVIVE A FUNDAMENTAL
BREACH OR BREACHES OR THE FAILURE OF THE ESSENTIAL PURPOSE OF THIS
AGREEMENT OR OF ANY REMEDY CONTAINED HEREIN; AND (B) TO FLEXRAIO AND ITS
AFFILIATED COMPANIES, THEIR SUCCESSORS, ASSIGNS, AGENTS, AUTHORIZED
FLEXRADIO DISTRIBUTORS AND THEIR RESPECTIVE DIRECTORS, EMPLOYEES, AND
INDEPENDENT CONTRACTORS.
IN ADDITION TO THE LIMITATIONS AND EXCLUSIONS SET OUT ABOVE, IN NO EVENT
SHALL ANY DIRECTOR, EMPLOYEE, AGENT, DISTRIBUTOR, SUPPLIER, INDEPENDENT
CONTRACTOR OF FLEXRADIO SYSTEMS OR ANY AFFILIATES OF FLEXRADOI HAVE ANY
LIABILITY ARISING FROM OR RELATED TO THE DOCUMENTATION.
Prior to subscribing for, installing, or using any Third-Party Products and Services, it is
your responsibility to ensure that the supplier has agreed to support all of their features.
Installation or use of Third Party Products and Services with FlexRadio System’s products
and services may require one or more patent, trademark, copyright, or other licenses in
order to avoid infringement or violation of third party rights. You are solely responsible
for determining whether to use Third Party Products and Services and if any third-party
licenses are required to do so. If required, you are responsible for acquiring them. You
should not install or use Third Party Products and Services until all necessary licenses have
been acquired. Any Third-Party Products and Services that are provided with FlexRadio’s
products and services are provided as a convenience to you and are provided "AS IS" with
no express or implied conditions, endorsements, guarantees, representations, or
warranties of any kind by FlexRadio and FlexRadio assumes no liability whatsoever, in
relation thereto. Your use of Third Party Products and Services shall be governed by and
subject to you agreeing to the terms of separate licenses and other agreements
applicable thereto with third parties, except to the extent expressly covered by a license
or other agreement with FlexRadio Systems.
The terms of use of any FlexRadio product or service are set out in a separate license or
other agreement with FlexRadio applicable thereto. NOTHING IN THIS DOCUMENTATION
IS INTENDED TO SUPERSEDE ANY EXPRESS WRITTEN AGREEMENTS OR WARRANTIES
PROVIDED BY FLEXRADIO SYSTEMS FOR PORTIONS OF ANY FLEXRADIO PRODUCT OR
SERVICE OTHER THAN THIS DOCUMENTATION.
3.3 COPYRIGHT INFORMATION
Copyright © 2013-2018 FlexRadio Systems
All rights reserved
Information in this document is subject to change without notice and does not represent
a commitment on the behalf of FlexRadio Systems. No part of this publication may be

FLEX-6400/FLEX-6600 Hardware Reference Manual
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Copyright 2018 FlexRadio Systems. All Rights Reserved.
reproduced, stored in a retrieval system, or transmitted in any form or by any means,
electronic, mechanical, photocopying, recording or otherwise, for any purpose other than
the purchaser’s personal use, without the prior express written permission of FlexRadio
Systems.

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Copyright 2018 FlexRadio Systems. All Rights Reserved.
4SPECIFICATIONS
4.1 GENERAL
Specification
FLEX-6400
FLEX-6600
Frequency Range (Transmitter)
•Rated Output Power @ 100W
nominal
160m - 6m (Amateur bands
only by country) MARS
optional
160m - 6m (Amateur bands
only by country) MARS
optional
•Transverter (XVTR) IF Output Port
100 KHz - 54 MHz
100 KHz –54 MHz
Frequency Range (Receiver)
•Low Band (First Nyquist Zone)
30 kHz –54 MHz
30 KHz to 54 MHz
•High Band (Second Nyquist Zone)
NA
NA
Emission Modes*
A1A (CW), A3E(AM), J3E (SSB),
F3E (FM)
A1A (CW), A3E(AM), J3E (SSB),
F3E (FM)
Frequency Stability
•Standard
0.5ppm TCXO
0.5 ppm TCXO
•With GPSDO Option (GPS Locked)
5x10-12 over 24 Hours
5x10-12 over 24 Hours
Antenna Impedance - Unbalanced
50 Ohms
50 Ohms
Antenna Tuner Load Range - Unbalanced
8.3 - 300 Ohms (80m –10m)
6.7 - 150 Ohms (160m and 6m)
8.3 - 300 Ohms (80m –10m)
6.7 - 150 Ohms (160m and 6m)
Standard Supply Voltage
+13.8 VDC +/- 15%
+13.8 VDC +/- 15%
Supply Current (Receive/Transmit)
1.7A Receive Typ., 23A
Transmit Max.
2A Receive Typ., 23A Transmit
Max.
Operating Temperature Range
0 to +50C, +32 to +122F
0 to +50C, +32 to +122F
Dimensions
•With Feet
7” (17.8 cm) H, 14” (35.5 cm)
W, 12” (30.5 cm) D
7” (17.8 cm) H, 14” (35.5 cm)
W, 12” (30.5 cm) D
•Weight
10.5 lbs., 4.8 kgs
11.1 lbs, 5.0 kgs
* - Other modes may be available through the addition of third-party waveform plug-ins.
4.2 TRANSMITTER
Specification
FLEX-6400
FLEX-6600
Transmitter Architecture
Direct Digital Up Conversion
Direct Digital Up Conversion
TX DAC Resolution
16-bit
16-bit
TX DAC Sampling Rate
122.88 Msps
245.76 Msps
Output Power CW/SSB/RTTY/FM (AM) at
13.8 VDC (nominal)
100W (25W)
100W (25W)
XVTR Port Power Output
0 dBm Typ.,
+10 dBm Max.
0 dBm Typ.,
+10 dBm Max.
Modulation
DSP Generation
DSP Generation
Spurious Emissions
HF: -55 dBc, 6m: -65 dBc
HF: -55 dBc, 6m: -65 dBc
Carrier Suppression
-80 dBc below peak output
-80 dBc below peak output
Unwanted Sideband Suppression
-80 dBc below peak output
-80 dBc below peak output
Transmit Frequency Response
Default 100-2900 Hz (Variable
50-10 kHz)
Default 100-2900 Hz (Variable
50-10 kHz)
Microphone Impedance
600 Ohms Nominal, 200-10k
Ohm
600 Ohms Nominal, 200-10k
Ohm

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Copyright 2018 FlexRadio Systems. All Rights Reserved.
4.3 RECEIVER
Specification
FLEX-6400
FLEX-6600
Receiver Architecture
Direct Down Conversion
Direct Down Conversion
Spectral Capture Units
1
2
Maximum Slice Receivers
2
4
Maximum Spectral Displays (Panadapters)
2
4
ADC Resolution
16-bit
16-bit
ADC Sampling Rate
122.88 Msps
245.76 Msps
Reciprocal Mixing Dynamic Range
1 KHz 110 dB, 2 KHz 116 dB
1 KHz 110 dB, 2 KHz 116 dB
Amateur Band Preselectors
3rd order
7th order contest bands, 3rd
order other bands
Spurious and Image Rejection Ratio
>80 dB
>100 dB
External Powered Speaker Output
Impedance/Level
10 kOhm / 2.6Vpp max.
10 kOhm / 2.6Vpp max.
Headphone Output
16 Ohm Minimum Load @ 21
mW
16 Ohm Minimum Load @ 21
mW

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Copyright 2018 FlexRadio Systems. All Rights Reserved.
5UNPACKING AND INSPECTATION
5.1 UNBOXING
FLEX-6400/FLEX-6600 radios are double packed to protect your investment. To remove
the radio, carefully cut the tape on one end of the outer carton and open the end flaps to
expose the inner carton. Remove the inner carton by placing one hand on the inner
carton while using the other hand to invert the outer box so the open end is facing down.
Carefully place the inner carton on a flat surface then remove the outer carton by pulling
up on the sides. Use caution not to let the inner carton slip out and fall.
Position the inner carton to the FLEX-6400/FLEX-6600 label is facing up. Carefully cut the
tape and open the flaps exposing your radio. Remove the upper packing foam and set it
aside.
I - Be sure to keep the carton and all packing material in case you ever need to ship your
FLEX-6400/FLEX-6600.
5.2 VISUAL INSPECTION
5.2.1 General
Note the orientation of the radio in the packing foam. It is important that the front of the
radio be properly aligned to prevent damage if further shipment is required. Remove the
radio from the foam and the poly bag. Retain this bag if further shipment is required.
! - WARNING: POLY BAGS CAN BE A SUFFOCATION HAZARD. DO NOT LEAVE THIS BAG
UNATTENDED AROUND SMALL CHILDREN!
Δ –CAUTION: THE POLY BAG IS VERY IMPORTANT TO PROTECT YOUR RADIO’S FINISH
SHOULD YOU EVER NEED TO SHIP IT. DO NOT SHIP THE RADIO IN THE PACKING FOAM
WITHOUT FIRST PLACING IT IN THE INCLUDED POLY BAG.
5.2.2 Radio
Inspect your FLEX-6400/FLEX-6600 radio for any physical damage due to rough shipment.
Remove the protective cover from the front display.
5.2.3 Included Accessories
•One (1) FLEX-6400 or FLEX-6600 Transceiver
•One (1) FHM-2 Electret Hand Microphone
•One (1) 6 ft. (1.8m) CAT 5 Ethernet cable
•One (1) DC power cord with Anderson Powerpole™ connectors
•One (1) SmartSDR for Windows installation and documentation CD

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Copyright 2018 FlexRadio Systems. All Rights Reserved.
•One (1) FLEX-6400/FLEX-6600 Quick Start Guide
5.2.4 Additional Items Not Included but Required
In addition to the supplied accessories, software and cables supplied with the FLEX-
6400/FLEX-6600, you will need to provide the following:
•An HF-Antenna or dummy load.
•An RF ground (if possible).
•Powered stereo speakers (computer type) or stereo headphones.
•A stabilized 13.8V DC power supply, capable of 25A or greater continuous duty.
•A Personal Computer (PC) running Windows 7 or above. Both 32 and 64-bit
operating systems are supported (64-bit recommended).
•A 100/1000BaseT Ethernet Access –either an open port on your computer or on
your local area network (LAN) Ethernet switch.
5.3 REPORTING DAMAGE
Please report any missing items or shipping damage to FlexRadio or your Distributor
immediately. It is helpful to take digital pictures of the damage to assist in resolving the
issue with the shipper. See the CONTACT US web page FlexRadio contact information.
You can always open a HelpDesk Ticket at https://helpdesk.flexradio.com

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Copyright 2018 FlexRadio Systems. All Rights Reserved.
6FRONT PANEL CONTROLS AND CONNECTIONS
The front panel of the 6400/6600 contains only the Power button and the radio’s
backlights. The Power button is used to turn the radio on and off and is illuminated with
a number of colors to indicate the radio’s operational state:
•FLASHING GREEN: Radio is starting or shutting down
•SOLID GREEN: Radio is in receive mode
•FLASHING RED: See Error Conditions below
•SOLID BRIGHT RED: Transmitting on PA
•SOLID DIM RED: Transmit engaged, but transmit interlocks are not ready. Refer to
the SmartSDR documentation for description of the transmit interlocks.
•SOLID ORANGE: Transmitting on XVTR port with low power
•SOLID PURPLE: Radio is performing a software update
•FLASHING WHITE: Radio is performing a reset to factory defaults
•OFF: Radio is off
When the optional GPS Disciplined Oscillator is installed:
•SOLID AMBER: Radio is off, GPSDO is powered for stability
•FLASHING YELLOW: GPSDO is warming up
•SOLID YELLOW: GPSDO is “holdover” mode (has lost satellites)
•SHORT FLASH BLUE: GPSDO is locking
•LONG FLASH BLUE: GPSDO is in “hold phase” mode
•SOLID BLUE: GPSDO is locked

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Copyright 2018 FlexRadio Systems. All Rights Reserved.
The power control is a “soft power control” that performs multiple functions depending
on the state of the radio. If the radio is powered off, momentarily pressing and releasing
the button will start the radio software. The radio takes approximately sixty seconds to
become fully functional.
Momentarily pressing and releasing the button when the radio is running will start an
orderly shutdown of the radio software. When the button is pressed, the button will
slowly flash green. At the conclusion of the shutdown, the button will either turn off or
turn solid amber if a GPSDO is installed. A full shutdown can take up to 10 seconds. It is
advisable to allow the radio to shut down in this way. During a shutdown, the radio will
save its settings, so ending the shutdown early by removing power from the radio may
cause a loss of settings.
Avoid removing power from the radio when it is performing a software update (power
button is solid purple). Doing so may result in the radio becoming unresponsive.
Holding the power button down for 4+ seconds while the radio is running will trigger an
immediate shutdown. This skips the database writing procedure, so any changes will not
be saved. This is not a recommended shutdown procedure for regular use.
Reset Procedure
With the radio powered off, press and hold down the power button for approximately 5
seconds until the Power LED flashes white, then release the power button. The radio will
start and will set all of its internal settings to their default values.
Error Conditions
Certain hardware and software error conditions cause the radio to stop operating and
display an error code by flashing the Power button light as follows:
•One red flash: Fan malfunction
•Two red flashes: Software crash
•Three red flashes: Boot failure
•Four red flashes: Input power over voltage
•Five red flashes: CPU overcurrent
•Six red flashes: Input power under voltage
In the case of a software crash, the error code repeats for about 15 seconds, then the
radio will reboot. In the other cases, the error code repeats until the Power button is
pressed, then the radio shuts down. An additional press of the Power button is needed to
restart the radio.

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Copyright 2018 FlexRadio Systems. All Rights Reserved.
7REAR PANEL CONNECTIONS
7.1 DC POWER INPUT
The FLEX-6400/FLEX-6600 is designed to operate from a 13.8 volt nominal DC supply
capable of supplying 25 amps of continuous current to the radio.
! –This unit must only be operated with the electrical power described in this manual.
NEVER CONNECT THE +13.8VDC POWER CONNECTOR DIRECTLY TO AN AC OUTLET. This
may cause a fire, injury, or electrical shock.
Δ –The FLEX-6400/FLEX-6600 requires 13.8 VDC @ 25 amps measured at the radio in
order to transmit maximum wattage. Multiple power cable connections between the
power supply and the FLEX-6400/FLEX-6600, a poorly regulated power supply,
undersized power cable and very long power cable lengths will result in a voltage drop,
especially under load. Any voltage deviation from 13.8 VDC will result in lower power
output that the 100W nominal specification.

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Copyright 2018 FlexRadio Systems. All Rights Reserved.
I - For best results, select a linear or switching power supply that is well regulated and
free of internally generated radio frequency noise. “Birdies” generated by a poorly
filtered supply can often appear as signals in the SmartSDR Panadapter display.
The Anderson Powerpole™ connector contains 45 Amp pins to minimize voltage drop
during transmit. The RED connection should be connected to the positive (+) lead of the
power source. The BLACK connection should be connected to the negative (-) lead of the
power source.
I - If you choose to use your own Powerpole cabling, be sure to properly size the wire
and the Powerpole connector to minimize voltage drop during transmit. Excessive
voltage drop can cause lower transmit power output levels.
7.1.1 Fused Internally at 30 Amps
The power input has a protective 30 Amp automotive “blade type” fuse inside the radio
case. In the event you ever need to replace the internal fuse, remove the top cover and
locate the fuse in the rear corner of the PA board just inside the case adjacent to the
Anderson Powerpole connector.
! –NEVER USE A FUSE WITH A CURRENT RATING HIGHER THAN 30 AMPS! FAILURE TO
PROPERLY USE THIS SAFETY DEVICE COULD RESULT IN DAMAGE TO YOUR RADIO,
POWER SUPPLY, OR CREATE A FIRE RISK.
7.2 TRANSCEIVER ANTENNA PORTS [1,2]
Transceiver antenna ports are SO-239 50 ohm connectors. Refer to SmartSDR
documentation for explanation on how to select which port is active.
! - WARNING: THE FLEX-6400/FLEX-6600 ARE CAPABLE OF GENERATING RF POWER
LEVELS OF 100 WATTS. HIGH RF LEVELS WILL CAUSE SEVERE RF BURNS. NEVER TOUCH
THE TRANSCEIVER ANTENNA PORT, AN EXPOSED COAXIAL CABLE END, OR A
CONNECTED ANTENNA WHILE THE RADIO IS IN THE TRANSMIT MODE.
! –NEVER CONNECT OR DISCONNECT ANTENNAS WHILE IN TRANSMIT MODE. THIS
MAY CAUSE ELECTRICAL SHOCK OR RF BURNS TO YOUR SKIN AND DAMAGE TO THE
UNIT.
! –THIS UNIT GENERATES RADIO FREQUENCY (RF) ENERGY. USE CAUTION AND
OBSERVE PROPER SAFETY PRACTICES REGARDING YOUR SYSTEM CONFIGURATION.
WHEN ATTACHED TO AN ANTENNA, THIS RADIO IS CAPABLE OF GENERATING RF
ELECTROMAGNETIC FIELDS WHICH REQUIRE EVALUATION ACCORDING TO YOUR
NATIONAL LAW TO PROVIDE ANY NECESSARY ISOLATION OR PROTECTION REQUIRED,
WITH RESPECT TO HUMAN EXPOSURE!