Strange Antenna Mystery Revealed?? Partly...

So I posted yesterday about the strange antenna array on top of a mast in the grounds of Hyde Cricket Club up Werneth Low. I asked on Transmission1 forum and after a healthy debate, one user posted a link to the website of Caravan International Corporation which supplies a very similar set up for a fixed ground station and also for mobile use. The system they provide is the Direction Finder TC-5400 System. I've included some information from their website:

The TC-5400 Series of general purpose automatic direction finder systems are intended for use in a variety of military, commercial or civil government applications. The model TC-5400 Series DF systems may be configured with a series of internal or external receivers and are compatible with a wide range of simple or sophisticated RF receiving instruments to include surveillance or amateur radios, spectrum analyzers or communications service monitors. The TC-5400 Series DFF Processor may be configured with a wide range of associated general purpose or mission specific fixed station, mobile, shipboard or airborne Direction Finder Antennas.  

The TC-5400-1 DF Processor is a goniometer type direction finder that uses a variety of DF Antennas. The DF Antennas may be Monopole, Dipole, Log Periodic, Annular Slot or other beam former, or various combinations thereof.   

The received signal is AM modulated by the processor-generated sine wave, at each output (quadrant) of the antenna. The signals are combined and fed to a receiver where it is AM detected. The audio base band contains the 124.8 Hz and other received signal characteristics. The AM detected signal is fed to the TC-5400-1 processor that selects the 124.8 Hz component, measures the phase angle relative to the reference phase and converts it into bearing information.   

The processor then adds to the bearing information any offset programmed at the front panel, and displays the resultant bearing in a 3-digit readout and a corresponding relative compass pointer. The processor continues to measure and update the front panel display at the selected slow or fast rate until the received signal is no longer present. At signal loss, the processor 124.8 Hz component is no longer present. At the loss of the 124.8 Hz component, the display is frozen, displaying the last bearing calculated and the processor resets until a new signal is present.

Image and information © 2011 Caravan International.

So it appears that the array is a direction finding system possibly for aircraft although a member on the forum informs me that it is nothing to do with Manchester Airport. Perhaps it is for government and military use. What exactly it is monitoring is anyone's guess but it is certainly an interesting setup and definitely something I've never seen before.

Thanks for reading!

73's, Lewis, M3HHY.

Manchester, UK.