Audio type RDF powered by a 9 volt battery.
Attach it to your transceivers antenna out put.
In noisy environments use a head set.
You listen for a null or no tone and the handle becomes the line of site of the hidden transmitter. The down fall is that its pointing to or away from the transmitter. With a little practice this wont be an issue.

Click on photo
to enlarge

NOTE: DO NOT TRANSMIT INTO THIS UNIT
YOU COULD DAMAGE BOTH THE RDF UNIT AND YOUR TRANSCEIVER.

        When you are at the final stage of some fox hunts you need gear to locate the hidden transmitter as quick as possible. I built an audible unit that is inexpensive to build and is not too large to carry around. Plumbers 1/2" CPVC pipe was used for the frame. A 555 timer is used to switch the antennas. I decided to use a loaded dipole antenna to shorten the total height. A 9 volt battery is used for power as the circuit has a small current draw.

The PCB lay out is very simple and there are not a lot of components. This project should be enclosed in an aluminum project box to protect it from the elements.

Click on the PCB photo to enlarge.

PCB Layout

The photo on the left of the resistor and diode show the physical connection. Try to make the diode leads the same length for each antenna. I used a lug to solder the diode to, so a connection to the bolt could be made. The same goes for the shield of the coax to the other 8x32 bolt.

Resistor Diode

The dipole elements are wrapped around 1/2" CPVC.
The out side diameter of this CPVC is 5/8".
I used 12 gage aluminum wire for the antenna elements.
These dimensions in the photo should get you very close to the 2 meter frequency. The wire wraps under the nut for a secure connection.

Antenna Element

Click here to view and down load schematic