Haystack Sample Es Ionogram

X-axis: vertical incidence in MHz, Y-axis: virtual height in km

The above clearly shows the effects of "blanketing" Es where any VI access to
the F-layers are blocked.  Notice also the multiple Es echoes caused by the
ionosonde pulses "vibrating" back and forth between the earth and the layer.

The foEs here is only about 5.5 MHz, giving a simple Secant Law MUF of
just around 30 MHz.