ARDOPOFDM is an experimental extension to ARDOP2. The higher speed PSK and QAM modes of ARDOP2 are replaced with OFDM modes. There are two bandwidths, 500 and 2500 and 4 modes within each bandwidth (2PSK, 4PSK 8PSK and 16PSK or 16QAM). The mode uses a modulation rate and carrier spacing of 55.555 Hz. The 500 mode uses 9 carriers and the 2500 mode 43 carriers. 

The code runs on Windows, Linux and my Teensy TNC.

ARDOPOFDM has one new configuration parameter, ENABLEOFDM, with a default of TRUE. Apart from the new data frames it has two new CONREQ frames, OCONREQ500 and OCONREQ2500 and a new ACK, OFDMACK. If ENABLEOFDM is set it will use and accept the OCONREQ frames and the OFDM data frames. For compatibility with ARDOP2 stations if it receives a normal CONREQ frame it will disable the use of the OFDM data frames. If ENABLEOFDM is set to FALSE it will use normal CONREQ frames and reject OCONREQ.

I haven't been able to evalutate it under a wide range of radio conditions, but initial testing looks promising. Under ideal condtions it is a bit over twice as fast as normal ARDOP (about 80% of the speed of VARA). Data frame length is a little under 5 seconds. Under ideal conditions performance in 2500 mode is

16OFDM 80 bytes/carrier, 3440 bytes per frame, approx 4600 BPS Net
 8OFDM 60 bytes/carrier, 2580 bytes per frame, approx 3440 BPS Net
 4OFDM 40 bytes/carrier, 1720 bytes per frame, approx 2300 BPS Net
 2OFDM 20 bytes/carrier,  860 bytes per frame, approx 1150 BPS Net

For Comparison 16QAM.2500.100

120 bytes/carrier, 1200 bytes per frame, approx 2225 BPS Net

As mentioned earlier this a experimental and modulation details and frame formats are likely to change as testing proceeds. It is really only suitable for people who a used to testing software.