Using Spectrum Lab with PERSEUS

PERSEUS is a direct sampling, software defined receiver covering 10 kHz to 30 MHz (or, without preselector, to 40 MHz). Technical details about PERSEUS are on the Microtelecom website .  

Since March 2008, Spectrum Lab directly supports this radio, based on the SDRDK (Software Defined Radio Development Kit), (c) Microtelecom s.r.l., Pavia di Udine, Italy . So thanks to IV3NWV, you don't need a bandwidth-limiting "virtual audio cable" between the original Perseus software and Spectrum Lab.

Installation

To use Spectrum Lab with PERSEUS, you will need the PERSEUS interface DLL and a few other files installed on your system. But if you have a PERSEUS connected to your PC, you will most likely already have the software which you receive with the radio (by Microtelecom) installed.

For various reasons, the files required to operate PERSEUS from SpecLab are not part of the installation archive. Download them from Microtelecom, or copy them from the CDROM which you received with the hardware. A list of the files which must be copied into the subdirectory "perseus_drv" is in this readme-file . (The directory "perseus_drv" is created in the SpectrumLab directory during installation, but it will be empty except for the readme-file).

After the Perseus USB driver is installed, and all necessary files are copied to perseus_drv, Spectrum Lab can talk "directly" to the radio. Because the USB connection to the radio can only be occupied by ONE application at a time, it is impossible to let Spectrum Lab and the original Perseus software running side-by-side (at least, not yet ;-)

To select PERSEUS for input (instead of the soundcard), open the "audio settings" tab in SL's configuration, and select "PERSEUS" in the list of "Audio Input Devices".
Note: SL doesn't check if the radio is really connected to the USB port in advance !

Alternatively, you can select one of the preconfigured PERSEUS settings in SpecLab (this is easier than configuring everything yourself):

• In the main menu, select Quick Settings..Image cancelling DC receivers (I/Q)..
  "PERSEUS, 125 kHz sampling, downconverter, adjustable audio filter"
• Wait until the receiver is initialized. The spectrum analyser (and, depending on which setting was selected, the audio output starts).

In this configuration, SL acts as a back-end for a software defined radio, including waterfall display and audio output (through the soundcard). How to set the receiver frequency is explained in the next chapters of this document. How to adjust the audio filter is explained in another document... but in short form, there are a few diamond-shaped controls on the frequency scale, which you can move around to change the audio bandwidth (for SSB and CW), the audio center frequency ("pitch"), and the RF center frequency ("VFO") within the current IF bandwidth.

SDR Control / Configuration Panel

To open the following control panel for the PERSEUS, select View/Windows / SDR Control Panel in SL's main menu:

SDR VFO tab / main control panel

Note: The control panel may look a bit different, because there are different radios, too ;-)

You can modify the radio's NCO (numeric controlled oscillator) in the "VFO" field. Either type the number, or click on one of the digits to place the cursor there. You can then increment / decrement the frequency with the cursor up/down keys, or with the mouse wheel (unlike SpectraVue, just pointing the mouse above the edit field isn't sufficient ! ).
The RF gain combo changes the preamp gain / attenuator. Some less frequently used settings (which are specific to the radio) must be set on the "cfg"-tab (config):

SDR Config tab

The radio's IF bandwidth (and, at the same time, the sampling rate) can be set on the "CFG" (config) tab of this control panel :

Notes:

• It may be necessary to stop and restart the external SDR before the new settings become effective. If SpecLab fails to do this automatically, or if the radio "stalls" when switching to the new settings, stop and restart it from SpecLab's main menu ("Start/Stop"..."Stop Sound Thread"..."Start Sound Thread").
• A sampling rate of 200 kHz (and more) creates a heavy load on the USB connection between the radio and the PC, and requires a relatively fast CPU. If you don't really need a large displayed bandwidth, select a lower sampling rate - especially when using a laptop running on batteries !

Other options on the SDR configuration tab are:

• SDR clock frequency ( and the [Calibrate]-button )
  This edit field contains the precise clock frequency of the A/D-converter inside the radio. For the PERSEUS, the nominal frequency is 80000000.0 Hz, but it can be calibrated if necessary. You can let the program calculate the precise value: Click the "Calibrate"-button, enter the frequency of a well-known reference (for example, Droitwich on 198.0 kHz in Europe), followed by the measured frequency. Use a large FFT, and a low sampling rate to get the best accurary of the frequency measurement.
  
• [ ] add VFO frequency in the spectrum display
  If this option is selected, the VFO frequency will be added to the frequency scales in the main spectrum display, and when modifiying the VFO frequency (via mouse wheel for example), the displayed frequency range in the spectrum display will be adjusted, too.
  Otherwise, the main spectrum display will only show the "audio" frequencies, and the display will not change when the VFO frequency changes.
• [ ] keep this panel on top of the main window (and other windows, too...)
  With this option, the small SDR VFO control panel will always be visible on top of Spectrum Lab's main window, even if it doesn't have the focus.
• "More..." (button)
  Opens a popup menu with the following options:
  
  • Use passband ripple compensation (for the FFT)
    (Not applicable for the PERSEUS yet).
  • Select FFT compensation file
    (Not applicable for the PERSEUS yet).

    
    

• "Apply" (button)
  Click this button to apply the changes (not required for the VFO frequency, which will be sent to the radio immediately).

Because the output sampling rates of PERSEUS are not integer multiples of the soundcard's standard sampling rates (like 11025, 22050, or 44100 Hz), you need Spectrum Lab's output resampling function if you want to send the (demodulated) signal to the audio output of the soundcard.