[time-nuts] WWVB Chronverter TrueModulator

paul swed paulswedb at gmail.com
Tue Sep 25 16:37:02 EDT 2018


Hello to the group.
I wanted to share with you the chronverter modulator that I am using. It
works with cheap clocks and good grade Truetime and Spectracom clocks.

The The truemod supplies -5dbm to the antenna in the basement ceiling. A
single wire loop antenna of 20' X 10' with a 1.72uf cap to resonate the
loop. Feeding with RG6 coax 100 ft -.5db loss, telco wire -15db at 60 KHz.
Bad stuff.
The radiation efficiency of the antenna is -50 db. Or 150 uv.
So though it works through the walls and floors it doesn't get much further.
Additionally through multiple antenuators many coax clocks can be driven.
USE a Isolation cap on the output. Forgot to add those to the diagram.

The TrueModulator can use other divider schemes 15.36/256 etc. Nothing
really special and depends on what you have on hand. Though I used TTL and
66ma @ 5V it turns out in 2014 I built the same thing for the 60KHz
remodulator with cmos and a 15.36 MHz oscillator that draws 11ma. Should
have re-used that.

The whole system chronverter, neo6, and modulator draws 150 ma.
Used a dead bug approach on a copper pc board to build it. Its pretty small
and very fast to build.
So all set for the day that wwvb goes dark, or not. Actually really like
this arrangement. May stay on for ever as it beats wwvb here on the east
coast. Sets the clocks anytime of day.
Want to thank Bob and Alex for design suggestions.

Regards
Paul
WB8TSL
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