DAB in L Band
Since we have this WBX daughterboard in our hands it was not possible to miss a quick test on the L band ! Thanks to the wide coverage of this little nice board. We could not forget from where the MMBtools suite is coming …. Canada ! In this country they have allocated 23 channels starting from 1452 MHz until 1491.184 MHz. The DAB system in Canada is officially designed as DRB for Digital Radio Broadcast. (EN 50248) Australia is using this band too.
In other area like Europe the L band is possible (1467.5 – 1492.0, divided in two sub band recommended for terrestrial, T-DAB and satellite S-DAB)
This little test was done on the channel 12 in the middle of the DRB band: 1472.000 Mhz Replacing the frequency in the command line and having a gain of 20 dB (g = 20) the card is giving a stable 2 mW.
The output at this frequency will generate upper harmonics higher that the inboard filter but to reduce in general any out band noise and spurious we recommend anyway to use additional filters if you plan to feed any external power stage.
Looking in the stock of old RF parts we found some good filters (taken years ago from old analog satellite modulators and placed before a Ku band up-converter). After a quick tuning, the filter is adjusted in the middle of the band with a 38 MHz bandwidth (band-pass). We could be more restrictive but this let us some room when playing around with the channels, as we stay on dummy load we don't take any risk to jam anybody.
The filter retrieved from old spares parts
The filter response in the middle of the band (Center = 1472 MHz)
The spectrum (from 20 MHz until 3 GHz)
The OFDM group on the channel 12 @1472.00 Mhz