I would find two of the best Audio ADCs I could lay my hands on. Some of these are incredibly good by any standard. Sampling the mixer outputs at approximately 96kHz with 16 bit effective resolution is well within the possible.
All the repeated steps of amplification/limiting to find the zero crossing can be almost entirely replaced by a a single FFT. You are not limited by the 96kHz sampling frequency in the timing of the resulting zero crossing, because you can interpolate between the sample points. On a Loran-C signal, I have been able to do zerocrossing measurements with 1nsec resolution, despite the fact my sampling clock was only 10MHz. You can calibrate out almost all the asymetries by simply flipping the input signals and pretty much all of them if you can also do A/B switching on which mixer feeds which ADC. I wouldn't at all be surprised if this is how TSC does it. Obviously, damn good electronics is still necessary to control cross-talk etc. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
