HAM ATS3a digital

Posted on Feb 7, 2014

I have managed to let the stock ATS-3A transceiver transmit nice BPSK31 `cq ok1iak`. The firmware of ATS-3A was modified to allow serial line control, which is performed over the DASH paddle pin in straight key mode. That means paddle will not work if in remote control mode. To enable both remote control and paddle woul

HAM ATS3a digital
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d need hardware modification of the stock ATS-3A. The only way to shape the BPSK31 envelope on a stock ATS is to key the transmitter on/off. The envelope is far from raised cosine, but the signal is not wider than of CW and the sidelobes will be hopefuly negligible at QRP levels. I tested common windows PSK31 programs how they will cope with that non ideal envelope. MIXW32, MultiPSK, DigiPan and PocketDigi worked well, WinPSK had occasional drop outs. Here is the screenshot of BPSK31 signal received on RadioShack DX-398. On the lower part of the screenshot the receiver may have been overloaded. RTTY or MFSK16 modulation patterns may be generated by ATS perfectly. Olivia uses symbol shaping, but I bet hard keying like in the case of MFSK16 will work good enough. The serial line hardware protocol is 1200Bd asynchronous, 8bit, 1 start, one stop bit. Because I am targeting mainly handheld computers, the serial stream is generated by a sound card in the 202 format and transformed to the 0/3. 3V digital levels by an external FSK decoder. The two tones are 1200Hz mark and 2200Hz space. The tones are converted to 0V for space and 3. 3V for mark. I did not implement ATS support into PocketDigi yet, I only wrote a simple C+ application to generate WAV sound files with various commands. Those WAV files may be played on a PC, Pocket PC or even on a mobile phone or MP3 player. I will be happy to provide modified ATS-3A firmware source...

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