Version 3.0.24 supports the FDM-DUO Transceiver.

Start the DUO with the 1.536 MHz bandwidth, this is best for lowest receive latency. Read the rest of the description on this page to properly operate the DUO.

Configuration

When you connect the FDM-DUO to your computer a playback sound device FDM-DUO Audio v1.04 is added, this is used by SDR Console to send IQ (transmit) data to the DUO. The device properties must be configured as below.

ELAD Menu

  • Elad menu item 30 TX Enable must be set to on.
        

Open The Sound Settings

  1. Open the Windows settings,
  2. Either select System, Sound or enter Sound in the Find a Setting field,
  3. In the Sound window select Sound Control Panel (highlighted).

Default Device

If  FDM-DUO Audio v1.04 has been selected as the default output device then you must select another device as the default output device.

Device Properties

In the Sound Control Panel:


  1. Open the  FDM-DUO Audio v1.04 properties (double-click on the entry).
  2. Select Levels , make sure the value is set to 100 (maximum).
  3. Select Advanced and make sure the default format is:
  • 2 channel,
  • 16-bit,
  • 48000 Hz (DVD Quality).
  1. Select Spatial sound and make sure the selection is set to Off .


Status Check

Confirm that the device has been opened:

  1. From the Console's Radio panel click Options, this opens the FDM DUO Options.
  2. Select then Transmit page.
  3. Check the device is shown as open.


Make sure the USB audio device (above) is correctly configured with the Level set at 100.

Settings

There are two ares of SDR Console where you configure the operation of the DUO:

  • Radio Panel - specific to the to DUO only,
  • Common - for example equalisation and gain.


DUO

The main options are selected from the Radio panel.
  • Rx Ant Enables a separate receiving antenna, connected to the SO259 RX connector.
  • Attn Enable attenuation of the received signal, Tx enables the attenuator while transmitting.
  • Filter Enable a low-pass and/or pre-selection filter.
  • Split Always set to Standalone (will be removed in a future kit).
  • Tx o/p Use either the SO259 RX/TX connector (max power 10W) or the SMA RF connector (max power 0 dBm, 1 milliwatt).
  • Tx pwr Maximum output power when High pwr is selected.
The transmit indicators at the bottom are
  • TX Overload,
  • FIFO size in milliseconds,
  • Input level, value is shown in dB relative to the theoretical maximum.

Common

See also the common Transmit options. Select Transmit options either by pressing ••• in the Transmit pane or by selecting Options from the Ribbon Bar, Transmit pane.

Shown below:
  • Master gain settings, you may need to boost the microphone by up to 20 dB, typically only 10 dB is required.
  • Envelope symmetry, normally the output from a microphone is not 100% symmetric
  • Equaliser, shown here is a high-shelf filter which boosts the output above 600 Hz.
  • RX Mute, this mutes the receiver while transmitting as the DUO runs in full duplex.

Microphone

When you select a microphone the output is shown in the Spectrum window.

In the example on the right the level is good without any extra processing, adding processing increases the output level, too much processing will result in distortion.

You should be able to modulate well without adding extra processing, if the level is too low you can boost the output by up to 20dB (see Gains, above). Adding Equalisation will also boost the output.

Digital Modes
When using digital modes do not use the processor.

Starting

The recommended bandwidth is 1.536 Mhz, this has the lowest latency and enough bandwidth for most ham bands.


SDR Console interfaces to the ELAD FDM-DUO:

  • DUO is set to Split, standalone
  • VFO-A is the receive frequency as shown on the DUP and corresponds to the center frequency of the waterfall
  • VFO-B is the transmit frequency
  • SDR Console sends IQ (SDR raw format) data to a USB soundcard which is created on your computer when you connect the DUO (see Configuration below)
  • The transmit mode (LSB, USB, AM, ...) is independent of any mode which may be shown on the DUO front panel, the DUO' VFO-B is set to USB so it can receive the IQ (above)


Latency

DUO delivers different samples per packet for each sample rate, so to determine the interval between data packets received take this size and divide by the sample rate.

From the table on the right a sample rate of 1,536 kHz will deliver a 'smoother' data flow, resulting in fewer audio pops and associated stuttering as well as lowest latency.

Buffering
Data received from the ELAD is buffered, the buffer is read at a steady rate by the main threads in the program to ensure a steady data flow.

About Sample Rates
All ELAD sample rates are native to the ELAD and supporting API, they are not created as a result of extra processing by this software

Latency

Sample Rate Sample Size Interval
192 kHz 12,288 64 ms
384 kHz 12,288 32 ms
768 kHz 12,288 16 ms
1,536 kHz 12,288 8 ms
3,072 kHz 49,152 16 ms
6,144 kHz 49,152 8 ms

Notes

Microphone

Using a microphone connected to the DUO is not supported, remember the DUO is under computer control.

PTT

PTT using a foot switch connected to the DUO is not supported, remember the DUO is under computer control. If you want foot switch / external PTT support see https://www.sdr-radio.com/ptt .

Power Output

If you select Maximum output power the DUO will deliver up to 10 watts. The output power is shown in the meters, the IQ level sent to the DUO relative to the maximum possible is shown in the radio panel.

Video