Tracking Transmitter Circuit - Stealth Carrier Demodulator

Silent or Pulsed Carrier To "Beep" Converter

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Silent Carrier To "Beep" Converter (Stealth Demodulator) - DDC

Resistors: 1/4 Watt
R1 = 10 OHM - ( Use A 1/2 Watt Resistor Here )
R2 = 10K
R3 = 1 MEG
R4 = 10K
R5 = 470 OHM
R6 = 10K
R7  = 1K
R8 = 10k
R9 = 500 OHM Pot
Capacitors: - Disc Or Electrolytic ( Electrolytic Shown with +/- ) 
All Low Voltage
C1 = .1
C1A = 22 MFD
C2 = .01
C3 = 6.8 MFD
C4 = .1
C5 = 6.8 MFD
Transistors:
Q1, Q2 = PN918  Digi-Key Electronics
BATTERY:
9 V.D.C. - Use a standard SPST switch for the on/off switch. The Positive  Side Of The on/off switch
connects to the circuit, the negative side of the battery to ground as shown on the schematic.
D1 and D2:
1N34A - Diodes
CHIP1:
LM555CN - Standard Timer Chip. Jumper Wires between pins 2 to 6 and pins 4 to 8
SPK:
Any 8 Ohm Speaker
J1:
This is a standard 1/8" mono female audio jack. Use a patch cord to the earphone or external speaker
connection, of your receiver or scanner.


audio converter circuit
There are many ways to modulate a Tracking Transmitter. Most of the time they are simple RF carrier transmitters. Modulation can be a warble picked up at the receiver end, a continuous tone such as 1000Hz, an up and down tone or any of a dozen ways. The problem here is that when you operate such a device in the normal scanner bands, modulated in that manner, someone - somewhere will intercept its signal.

I have engineered quite a few beacon ( Tracking ) transmitters over the years using the Stealth Method of being able to conceal a silent carrier using a pulse without modulating it in the standard scanner bands, thereby defeating the chance of anyone intercepting or locking onto its signal by using the device below.

My method of choice, was conceived many years ago when, in the field working as an Investigator we often would signal each other thru a series of clicks on the mike button - what is called "Breaking Squelch."

I came up with this device that allowed those series of clicks to turn into a series of beeps or an audible tone.

In later years I applied the circuit to silent carrier Tracking Transmitters. It works by turning a silent or pulsed carrier into a beep at the receiver. It only requires a patch cord from the scanner ear port to this device. Operation of this unit is detailed on this page.


Operation Of This Unit:

Turn the squelch off on your scanner ( adjust it to
where you hear noise coming from its speaker
(Scanner ). Plug a patch cord into J1 from this unit
into the ear port and the volume up on your
scanner. Turn the on/off switch of this unit on. You
will hear nothing from this unit out of it's 8 ohm
speaker. When your scanner detects a silent carrier
( such as used in carrier make/break transmissions
) - this unit will sound off thru it's speaker as a
"BEEP." In other words, when a transmitter is
keyed with only a carrier, your scanner squelch is
interrupted with silence - and the DDC unit,
reverses that and emits an audio tone.