Buck, N4PGW wrote:
"Is it something duplicable with Radio Amateurs in general or does it
require some special type of equipment?"

Much British success in WW-2 in eavesdropping on German transmissions
had as much to do with information processing as it had to do with its
interception.

Germans used an "Enigma Machine" which was easily reset for a new code.
They often changed the code and it was quite complicated. Germans used
the machines to encode and decode their confidential messages. Early in
the war, an Enigma Machine was captured. British code experts worked
long, hard, and smartly to determine how the machine worked and broke
its codes. Afterwards, the British were silent parties on the German`s
war partyline. The British sometimes feigned ignorance so as not
announce their access to Germany`s most secret information. It was a big
factor in victory.

Stationary direction finding can take the directional antenna arrays
used for transmitting and use them for receiving insteaad. Reciprocity
means that the reception pattern is identical to the transmitting
pattern. I have no idea what the British did in their enemy reception
stations in WW-2. For HF, they could have used Yagi-Uda`s on rotators
and indicators. They also could have used crossed loops or Adcocks,
feeding a goniometer and not rotated the antenna. Terman shows how this
is done on page 1051 of his 1955 edition.

During the "Cold War", when I worked in HF broadcasting, Radio Free
Europe diligently monitored, recorded, and processed broadcasts from
behinnd the "Iron Curtain". All the Communist news and commentary that
was fit to broadcast from their point of view. To pick the desired
transmissions from among the babble, some RFE receiving stations had the
appearance of medium-wave multi-tower broadcast stations. Towers were
tuned and phased to null interference and to grab the desired
transmission. Other stations used sizeable loops. Some had air for a
core and some had huge ferrite cores. Whatever proved best was used in
any case..

Hams can surely use directional antenna systems.

Best regards, Richard Harrison, KB5WZI