Amplitude, Phase, and Doppler Effects on WWV Reception

Here's a Lissajous pattern plotting reception of WWV's 5 MHz carrier (Y-axis) against a local frequency standard (X-axis).

Shifts in phase evidenced by changes in the eccentricity of the ellipse are due to changes in the ionospheric propagation path between WWV's transmitter in Colorado and my receiver in NJ.

What is fascinating (although not too evident in this video) are the quick 180 degree phase reversals that frequently occur after the signal comes out of a sudden deep fade.

Category:

Science & Technology

Tags:

• amateur
• radio
• wwv
• shortwave

[5UP7]

Yes, the video implies that brief and deep fades on HF are the result of the signal splitting into multiple paths that arrive at the receiver at equal amplitude, but opposite phase.

Occasionally, the signal "peaks" very suddenly as the amplitude of the signals add perfectly in phase.

Since VHF/UHF mobile picket fencing is a product of multipath reception, it might result in a similar amplitude and phase plot.

[uploadJ]

Rayleigh Fading - maximum signal peaks of about 6 dB, but fades that have nulls that can be 30 or more dB in depth; seems to be what happens with HF fading too. 5/5

[msf60khz]

When two signals nearly cancel, the residual signal is in quadrature. There is always a rapid 180 shift associated with a null, in antenna patterns, transmissions lines etc etc. In the WWV case, if signal strength variation occurs there are probably two paths . However, even if just one path, as it varies in length it will cause the ellipse to vary from circle to straight line.

[hyvahyva]

Very interesting... I'm guessing the deep fades are probably due to changes in the ionosphere's level or movement of reflective nodes?

I kept thinking this looked a lot like the 'picket fencing' you get when the signal begins to flutter on a vhf/uhf mobile.