Aerial Coupling Equipment J enables Wireless Set No. 22 to be used under cover at a distance of 50ft from the aerial. The equipment was provided for use with vertical aerials up to 34ft. A plug-in RF Ammeter 1 Amp No. 3 (or a tuning lamp) is used when tuning the Aerial Unit J. Note that this particular unit has a tropical finish and consequently designated 'T'.
Inside view of Aerial Unit J showing the variable inductor similar as used with Wireless Set No. 22.