rectangular recess or notch 19 of sufficient depth and width to receive a circuit board 20 which holds the components of a radio transmitter of known design preferably the transmitter is a crystal controlled transmitter operating at a selected frequency within one of several vhf high band frequency ranges including the 140 174 megahertz range also in accordance with this invention the outer housing member 11 is further modified by the addition of a second internal wall or web 21 extending parallel to and spaced below the interior wall 18 wall 21 is formed with a rectangular recess or notch 22 of the same depth and width as the recess 19 in wall 18 as shown in fig6 the transmitter circuit board 20 near its upper end rests on the upper interior wall 18 at the bottom of its recess 19 and as shown in fig6 and 9 the transmitter circuit board near its lower end rests on the lower interior wall 21 at the bottom of its recess 22 in accordance with another important feature of this invention the inside of the outer wall 12 of the outer housing member 11 has a shallow recess 23 of generally rectangular outline the lower edge 24 of this.