The OFDM signals that the SSTV folks use with programs such as WinDRM
have three pilot tones at 725, 1475 and 1850 Hz. Perhaps they do
something similar to what you suggest since it uses the same basic
modulation scheme of DRM. They are called (FAC's) frequency acquisition
carriers and use phase information of the tones.
73,
Rick, KV9U
Walt DuBose wrote:
>I was exchanging E-mails with one of the individuals who was initially
>involved
>in writing the MIL-STD that created multine tone modems and the use of a
>single
>tone with no modulation in PSK modes to track and correct for doppler shift.
>
>They could not understand why "hams" did not just add another tone with no
>modulation to compensate for doppler on HF paths? They mentioned that surely
>it
>wouldn't take up that much more bandwidth and would add so much to the
>robustness of our PSK modes.
>
>73,
>
>Walt/K5YFW
>
>
>
>
