[time-nuts] Spectracom 8161 "Standard Frequency Receiver -, Oscillator" for WWVB (and question...)

[Martin VE3OAT]

jimlux wrote :

 > And, just as with Omega (10-15 kHz) the height of the ionosphere
 > changes the effective height of the "waveguide" through which
 > the surface wave propagates.

Exactly!  Folks, this isn't simple "reflections" between the earth and 
the ionosphere.

At VLF frequencies the wavelength is comparable to the height of the 
ionosphere (D layer, 70-90 km above earth's surface), so we have 
"waveguide propagation" in the "earth-ionosphere waveguide".  The WWVB 
phase changes occurring during sunrise and sunset transitions are 
caused by the change in the dimensions of the waveguide.

Quite a different situation from what we are used to at HF/VHF.

... Martin   VE3OAT