Well, our Telefunken curtain arrays have a typical gain of 20-23 dB.

TeleSource has just installed two TCI (Technology for Communications
International) 611VS curtains at 270 and 305 degrees for the low band
(6-12 MHz) here on Tinian. 3db azimuthal beamwidth is variable between
20-36 degrees, and they are vertically slewable in 4x4 and 4x6 mode.
Gain is between 16.6 to 24.1 dBi, and tower height is about 470 feet.

I would daresay if a 3-5 degree beamwidth had ever been made, it is
probably experimental. The physical size makes it prohibitively
expensive as well as mechanically improbable.

Al in CNMI
IBB Station engineer (contract)

I wonder if shortwave broadcast antennas have been used for
signals/communications intelligence?

RG