The FUNcube Dongle Pro+ has the same design aims as the original FUNcube Dongle, but we’ve taken on board many of the comments about the original FCD, and improved both the performance and the functionality. Indeed, although from the outside it might look similar, it’s an entirely new design.

On the performance side, we’ve added 11 discrete hardware filters to the front end, including narrow SAW filters on amateur 2m and 70cm bands. This has a hugely beneficial effect on front-end blocking, particularly at VHF.

There’s also a new LNA used with far better performance, improving the OIP3 to 30dBm (was about 10dBm). In addition, the RF stages are at 3.15V compared to the original FCD’s 1.5V, innately improving dynamic range.

Also added is a TCXO rated at 0.5ppm, althogh typically in practice tests show the accuracy at 1.5ppm (the original FCD used 20ppm crystals).

For functionality improvements, we also took the opportunity to extend the frequency range to add HF, MF and LF, and to provide complete coverage of the amateur 23cm band. The receiver range is now 150kHz to 240MHz and 420MHz to 1.9GHz. In our first 20 units, all have covered 150kHz to 260MHz and 410MHz to 2.05GHz.

Similarly, the sample rate is increased to 192kHz.

Internally the ADC depth used is 32 bits. Initial firmware will provide access to 16 bits of ADC resolution.

The local oscillator phase noise is far less than the original FCD, and typically once an antenna is connected the once-familiar 0Hz spike disappears into the noise. The LO resolution is also down to about 0.5Hz, even at L band.

Some quick stats…

o 240 parts (original FCD: 100)
o 100 BOM lines (original FCD: 28)
o Parts mounted on both sides (original FCD: parts on one side)
o Six layer PCB, two are solid ground planes (original FCD: double sided)
o 21 ICs, 122 capacitors, 49 inductors… on the same space as a 40pin DIP package