The SDR-DUO has been on the bench in day to day use for about 2 months now so it’s time to talk about how it works out in “real world” use. The Italian made FDM-DUO has to be the most versatile, well designed, and well thought out SDR system currently on the market. With some of the major amateur radio manufacturers beginning to bring SDR systems to market, they would do well to take a look at what Elad has done here. The FDM-DUO can be used as a very pleasant and capable standalone transceiver as well as a very powerful SDR system when coupled with Elad’s brilliant FDM-SW2 SDR software. The FDM-SW2 software has to be hands down the best SDR programs out there featuring a wide array of useful features currently unmatched by other entries. It’s also nice to know that Elad isn’t resting on their laurels when it comes to software. Elad is continuously making improvements and adding new features to the FDM-S2 software. The FDM-DUO concept is exactly what a lot of radio hobbyist have been looking for. A pleasant easy to use standalone direct sampling SDR transceiver for times when you just want to turn it on and use it without fiddling with a computer, but has the option of being turned into a very capable SDR system when connected a computer. The FDM-DUO receives from1 0KHz – 54MHz and will transmit with about 5 to 8 Watts out on the Amateur radio bands. Another rather unique feature of the FDM-DUO is being able to use the radio standalone along with a 3rd party software application such logging software or digital software. In other words, you can simply connect your laptop to the FDM-DUO via two USB ports and use something like Fldigi to operate PSK without having to use the FDM-SW2 software.  Also when using the FDM-SW2 software, it is not always necessary to use virtual audio or serial cable programs since the FDM-DUOs’ CAT and Line in / out USB ports can be used. One less complication for people not experienced with setting up virtual audio and serial ports. In a lot of ways the Elad FDM-DUO is perfect for the radio hobbyist that wants to ease into SDR gradually. You can start off in the more familiar world of the legacy standalone mode type of operating, then very easily add digital operating modes software, and then gradually ease into full SDR use. Even very experienced users will find a lot to dig into with FDM-DUO the FDM-S2W software. Ok, what’s all this going to cost? In the USA the Elad FDM-DUO goes for a very reasonable $1149 from the US Elad Store. However you may have to get in line because they seem to go pretty quickly when they are in stock. Support is either provided directly from Elad or the Elad Yahoo user group.

Standalone radio:
Frequency range: 10KHz – 54MHz
Direct sampling receiver operating @ 122.88MHz ADC: LTC2165 16bit
DDC (Digital Down Converter) FPGA Xilinx Spartan.6 family down to 192Ksps
DDC, Filter & Demodulator ARM STM32F429 floating point microcontroller
Demodulation CW, LSB, USB, AM
LSB,USB Filters selectable 1600-3100Hz Bandwitdh with 100Hz step plus 4000-5000-6000 Hz Bandwitch
AM Filter selectable from 2500 to 6000Hz with 500Hz step
CW Filters 2600Hz-1500-1000-500-300-100Hz Bw plus 4 Cw peak filters applied after 100Hz Bw to obtain an overall filter of 20Hz Bw
Noise Reduction 10 levels
Noise Blanker 10 leves
VFO A, VFO B, 199 MEMORIES with Frequency/ Alphanumeric label visualization, programmable by FDM-SW2 memory manager
Programmable BAND selections: selectable up to 20 quick recallable memories from 180 to 199

DDS AD9957 with 368.64 MHz clock
Microphone input ADC 48KHz @16bit selectable gain -12dB to +12dB
Key and Paddle input for CW operation (Iambic A e Iambic B selectable)
5W min power output from 160m to 6m, 8 W typ output @14MHz
PTT Output connector to drive external amplifiers

All programmable components (ARM RX, ARM TX, Flash for FPGA, User Interface microcontroller and USB controller) are firmware upgradable
CAT input USB control interface with FTDI controller
Antenna connectors: RTX SO-239, RX SO-239
Monitor output: 0dBm SMA to be used as test equipment allow the use as a Digital RF Generator
LCD Backlight RGB programmable, depending on function can change the colour (RX, TX , PC remote control)
10MHz Reference input connector: SMA
Power supply: 2.1mm DC Plug 13.8VDC RX consumption 500mA typ (13.8V) TX: tbd
Size: Witdh 180mm (7.00″) x Depth 155mm (6.10″) including Knob and connectors or 130mm (5.10″) only enclosure x Height 70mm (2.75″)

Additional capabilities when used with the FDM-SW2 software :
Up to 9 simultaneous receivers combination ( 1 on center frequency stand alone, 4 FDM-SW2 in fist 192kHz channel and 4 in the second 192kHz channel
Each receiver on FDM-SW2 have a dedicated Audio Channel and a dedicated CAT to be usable from external application with Virtual serial ports and Virtual Audio Cables
Selectable  Band configuration from 192kHz to 6MHz DDC bandwith (192,384,768,1546,3072,6144Ksps) 2 channel 192Ksps, 2 channels 384Ksps
RX and TX SPLIT mode operation: VFO A for RX while VFO B used for TX (with FDM-SW2 simple click operation to change TX frequency)
CW skimmer integration management (DX Spot visualization & tuning capability)
Direct digital Modulation using USB soundcard based on CMedia chipset digitally interfaced with ARM floating point microcontroller and DDS

What you get in the box

The FDM-DUO comes well packed in a rather plain brown box. Inside the box, you will find the FDM-DUO and a handheld microphone. The mic is pretty basic with a PTT button and a couple of up and down buttons on the top that can be used for tuning the radio. The mic connects to the back of the radio via a RJ45 type connector. Also included is a very generous cable pack which includes 3 usb cables and a couple of stereo audio patch cables. You will also find the power cable that needs to be attached to a 13.8 volt power supply. There is also a smaller pack that includes some lesser used connectors such as not wired DB9 type connector for the accessory jack and a USB adapter cable used for firmware updates. You will also find a USB flash drive that contains the FDM-SW2 software, user manuals, and other software. You might want to hop on over to the Elad software download site and grab the latest FDM-SW2 software at some point.

5 thoughts on “Elad FDM-DUO – SDR Done Right!”
  1. Since I first saw this radio at Dayton in 2014, I thought that this was THE way to build a radio. I’ve had mine for over a year, and still discover hidden gems.

  2. Have had this radio since last christmas and I am very pleased. The undersampling and 0dBm out is a gem for the experementing ham ! The learning curve is a bit steep, hope someone writes a book (like Fred Cady´s on the KX3) for a more easy to read tutorial manual. So many good things in this box,but the crisp RX/TX audio and the filters are specially worth mentioning. And AT LAST a radio with no spurs tuning forward or backwards when exploring the bands,not even when hooked to a computer.
    In all very pleased, Carl , Sweden.

  3. With that additonal receiver antenna connector can you set the radio to listen on one antenna and transmit on another and have receiver muting automatic on QSK transmit?

  4. Only had this excellent rig a few days. It does take a little getting used to. The only negative for me at the moment is the audio from the Inbuild speaker. Obviously with a small speaker I don’t expect hi fi, but the volume output is very low even with GAIN turned up. With the phones plugged in…brilliant, but if I took it portable as a stand alone and forgot the phones…! In the shack I use the phones plugged into the phone socket of the PC powered speakers…excellent! Still experimenting with the great software.

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