Auckland Radio at Musick Point had a medium-wave direction-finding antenna of the Marconi-Adcock type, erected at the high point of the present golf course, where the road curves around to the eastern side.
There were four 100 ft steel stayed masts standing on porcelain insulators and connected to a coupling box in the centre, which had a wire cage sense antenna suspended from the triatic stays.
There was also an extensive earth mat radiating out from the masts.A multi-coaxial cable ran to the receiving station where the DF receiver was installed.
The receiver was a four stage TRF following the radiogoniometer, which was a rotating loop inside four quadrature coils. The loop was turned on a scale to indicate the direction of the received signal.
The tuning range of the receiver was in the 200 to 600 kc/s range. There was a heterodyne oscillator to give an audible beat note.
The sensitivity on the receiver and antenna system was such that it was possible to hear Australian broadcast stations at the bottom end of the band during daylight hours.
The whole receiver was housed in an enormous console along side the 500 kc/s watch position. This console was last known to be at MOTAT, but is now lost.A daily calibration check was made by the operators on a known station, and three-monthly calibrations were made by the technical staff by setting up a 5 watt oscillator-amplifier at surveyed points on the land area around the station at a distance of two to four miles.
The seaward sector was carried out by using a Navy or Marine Department vessel which carried field staff and circled the station from Cockle Bay at Howick to around Bean Rock, while a surveyor noted the direction of the boat with a theodolite and called it to stop when one of the calibration points was reached.
The boat then headed towards or away from the masts while making the calibration signal on CW.During one land sector calibration, a newer technician who had not been on this excersise before was in the field and was called on the 2045 kc/s phone link to make the transmission on 500 kc/s. The transmitter was heard: Z-L-E- silence.
Then a plaintive voice was heard on 2045, “What’s ‘Y’ in morse?”
On the decommissioning of the MW DF, the masts and concrete anchor blocks were sold to a local amateur radio operator who later erected one of the masts at his Pakuranga property and was to use the others to make bridges over a stream on his farm.
During the lowering operation one of the masts got out of control and came down with such a crash that it flattened one of its square sides, it was however later straightened.
The anchor blocks were sold as boat moorings.
There was also a short wave DF hut and mast not far away from the MW DF which was used for aircraft positioning along with another at Waiuku operated by CAA.
The SW DF could not be operated from the receiving station and the operator had to cycle up to the hut when a fix was requested. This DF had its own remote controlled calibration oscillator.
The hut was located near the group of trees half-way along the road towards the MF DF site.
Thanks to Eric ZL1ADE for this information.