The AN/TRD-4 is a complete transportable radio direction finding station that covers the frequency range from from 540 kHz to 30 MHz with separate facilities for direction finding, intercept reception, communication reception, field telephone communication and frequency measurement. All these are housed in a  S44A/G shelter and are arranged around three individual operating positions - one each for  D/F, intercept  and communication operators. Special tools , test instruments and field spares are stored in bins and chests within the shelter. Two separate Adcock arrays are required to cover the frequency range of the set. The low frequency array covers 540 kHz to 10 MHz while the high frequency array covers 8 to 30 Mhz.   

A MOPA (Master Oscillator Power Amplifier) permits communication up to a range of 1 mile. 

This general diagram shows the low frequency Adcock array with ground mesh, the exterior of the shelter and the three operating positions. In the distance is the power generator. (US Army Image)

Low and high frequency Adcock arrays. (US Army Photo)

The D/F receiver consists of (top to bottom): Transmission Line Switch,  Goniometer, CRT based Azimuth Indicator and the R-390/URR receiver. (US Army Photo)

The is the left view of the shelter whose exterior dimensions measure 139 inches by 74 inches square.  Click on image to enlarge. (US Army Image)

Credits and References:

1) TRD-4 Reference Manual TM11-688. Provided by US Army,  Ft. Monmouth, NJ.

Aug 10/06