[time-nuts] WWVB remod works with spectracom 8170 and netclock/2 other updates

paul swed paulswedb at gmail.com
Sat Jun 22 17:44:01 EDT 2013


Thanks to Dave on Time-nuts I have been able to verify that the wwvb
remodulator works fine with the netclock/2 or the spectracom 8182. On the
8182 if you use it with the remodulator it senses the antenna. You need a
1.8K resistor to ground to make the rcvr believe an antennas there. Its
actually a bit fussy about this value.

Quite a bit of other information learned today.
The xtal can be adjustable and you can get it above the frequency. The
series resistor that controls the drive seems to be key. Higher lowers
drive increases isolation from the inverter output capacitance. I mean a
change from 20K to 270K. That said this creates a longer startup period
normal for low freq oscillators. So I don't have the best solution yet. But
I was able to add a 2-10pf trimmer and adjust above and below 60Khz.
Easiest way to adjust is by a dual trace scope and another 60 KHZ source.
Counter will work but its a lot slower process.

Output section delivers -65 db for a high and -82 for a low. Pretty good
guess. I changed it to a 10 db spread. The clocks don't like that at all.
Turns out a higher spread is better.

Have had the system operational at 3V and am back at 5 for now till I get
the oscillator figured out.
Needed to add a inductor in the power supply lead between the rcvr and the
digital section had feedback creep in.
Regards
Paul
WB8TSL


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