Bruce Griffiths wrote: > Your original loop antenna should have a lower phase tempco > (particularly if a lower TCE coil former than a plastic lid is used) > than any ferrite antenna, particularly so if the antenna is resonated. > Quartzlock have abandoned the use of ferrite antennas and substituted a > balanced shielded loop antenna for this reason for their VLF phase > tracking receivers. >
When I built a DCF77-DO (selective I/Q front end, the rest a software radio in an AVR), I ran into this problem of phase tempco. A loop was better, but it was unhandy, and I still had phase drift in the amplifiers, filters and mixer propagation delay. My fix was to have a tiny transmitter loop near the antenna (just the feeder cable termination resistor). Once in a while the microcontroller generates a 77.519kHz carrier, gets a phase measurement using the same frontend and I/Q mixer, and uses this for compensation. DCF77 does wiggle quite a bit at dawn, plus there is the occasional 1us phase adjustments at the transmitter end. http://n1.taur.dk/dcf/ (~100km NNW of PHK) I recall having seen better than this with Loran? /Kasper Pedersen _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
