Tracking transmitters are not that hard to make. The schematic, above, is for an animal tracking transmitter that generates a pulsed continuous wave (CW).
The complete transmitter, including the battery, weighs only 8 to 10 grams (less than two nickels) and is only slightly larger than a man's thumb nail. The ground range is 3/8 to 1/2 mile with a good receiver and antenna system -- less if the antenna on the transmitter is reduce or eliminate and the receiver is a simple radio box (as is the Deben receiver)
This transmitter design is from the American Institute of Biological Sciences Bioinstrumentation Advisory Council information module M15 prepared by William W. Cochran, December 1, 1967.
It is hard to be sure, but I believe this is the "original" Deben collar. Here are the parts:
X = Crystal, type FM1. 3rd overtone for 145-160MHz, 5th overtone for 220 MHz
Q = Transistor, Amperex type A415 (original type specified). Others that can be used include NTE 107, MPS6507, and 2N3904.
R2 = 1500 ohm, 1/8 watt
R1 = between 80K and 600K, 1/8 watt. This resistor determines the "beep" rate and is effected by battery voltage and the transistor selected.
C1 = Subminiature 15 mmf capacitor
C2 = Subminiature .001 mf capacitor
C3 = 2mf subminature capacitor
ant = 12 inch
L1 = 12.5 to 13 turns of #36 enameled wire wound on a 1/8 inch form and removed.
L2 = 4.5 turns of #32 enameled wire wound on a 1/8 inch form and removed.
wire = wire used to provide capacity to the animal
B = Battery, mercury type, 1.5volt
A photocopy of the out-of-print original publication for the M15 Animal Tracking Transmitter can be had for $5 from: http://www.jbgizmo.com/page5.html All of the components can be had for about $15.
For anyone that wants to play with a ready-made bug or tracker, the folks at hobbytron.net sell a 3v FM bug transmitter for just $20 (picture below), while full instructions for building an FM tracker can be read at FM Tracking intructions from JB Gizmo at http://www.jbgizmo.com/page21.html