HELLs BELLs – Hellschreiber on a dsPIC



Hell’s Bell’s is a stand alone Hellscheiber and SSB TX exciter . It is the big brother of Scriber.

The assembly source code  available from the download link below, runs in a Microchip dsPIC 33EP64GS502, and with the addition of some simple filters, provides the audio functions required for an SDR SSB / Hellschreiber transmitter. It accepts an amplified mic input, a PTT line & RS232 control I/O and provides I/Q analogue outputs and TX select to drive the transmitter.

Hells Bells is a .s (ASCII) file and should load and assemble directly in Microchip’s X lab IDE and then download into the dsPIC chip via a PICKIT 3, it may also be viewed in Notepad. (For best reading in Note Pad, set the Format>Font to Lucida Console, 9pt). The source code file contains details of the minimal hardware required.

The output sample frequency is 1MHz, requiring only simple passive RC filters to provide clean baseband I/Q for use in direct up conversion transmitters. Additionally, the I/Q outputs may be frequency offset (via RS232) anywhere between Baseband (0Hz) and the Nyquist limit (500KHz) with 16Hz resolution. This provides a TX tuning range of up to 300KHz with fixed frequency I/Q up conversion or direct RF drive for LF & MF transmission (2200m/630m bands) and 455KHz mixer up conversion, but requires more complex anti alias filters than simple baseband use.

Please Note:  This software is under active development and as such is a Beta software release, ie. it works but has a few loose ends and minor bugs to be sorted, feedback is welcome via ‘the Contact pulldown.

HELLS BELLS v0.9 (beta)  →    Download