Crazy George wrote:
"I think Steve would be interested in hearing a methodology for DFing a
non-stationary signal, as would I."

Terman says on page 1050 of his 1955 edition:
"The errors in bearing caused by downcoming horizontally polarized sky
waves can be eliminated by replacing the loop antenna with an Adcock
antenna, which in its simplest form consists of two spaced vertical
antennas, connected as shown in Fig. 26-28."

The ARRL Antenna book also gives information and says construction is
not critical.

Best regards, Richard Harrison, KB5WZI