[time-nuts] More ES100 WWVB Measurements

[brucekareen at aol.com]

On Mon, 31 Dec 2018 17:47:56 -0800 Wayne Holder <wayne.holder at gmail.com> wrote:

Interesting thought. I wonder if anyone has tested WWVB reception in a
deep underground location such as a sub sub level in a building or parking
garage?

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Many years ago when the San Francisco rapid transit system (Bart) was getting ready to open a tunnel under San Francisco Bay, a radio station I was affiliated with, operating on 560 kHz, was preparing to do an underground broadcast at the east end of the tunnel.  Radio reception was desired for timing and coordination as telephone lines, other than the broadcast circuit, were not yet available.  Portable radios produced no trace of a signal -- only noise.  I took down what I called a resonant-ring antenna, basically a three-food diameter ring of one-inch copper pipe with mica capacitors in the gap and tuned to 560 kHz.  The feed connections were loaded with resistance to produce a 10 kHz bandwidth as the natural response of this loop was only about 1 kHz between 6 dB points.  With the loop underground, bringing a transistor radio within a couple of feet of the loop produced a strong clear signal.
I believe a similar loop would provide underground WWVB reception.
Bruce, KG6OJI