XMT - Crystal Controlled FM Transmitter
The Original Circuits Below Were Built and Sold - In The Thousands To Law Enforcement. Their Original Research and Development Cost , By Today's Standards, Would Total - Well Over A Million Dollars.
The Quality and Performance Of Any Electronic Circuit, primarily the crystal controlled transmitter circuits shown here - depends on the quality of the Electronic Components used in its assembly.
Digi-Key Electronics is a quality supplier of Electronic Components and there is - no minimum order amount required. Digi-Key Electronics is the recommended electronic component supplier for all of the Crystal Controlled Transmitter Circuits listed here on Radio-Circuits.Com
|he XMT Transmitter Generates 125 MW of RF Power and Is operates in the upper VHF band. It can be received on a normal scanner. Narrowband Frequency Modulated with No-Drift. Long Battery Life and normally used as a "Concealed" FM Room Bug. Can be received up to a thousand feet away - and "Transmits Everything" it picks up. Works with just about any crystal you plug into it - so extremely versatile. Can also be worn on the body. About the size of a matchbox.|
Parts List: Circuit # XMT - Xtal Controlled - 125 Mw
Resistors: 1/4 Watt
R1 = 10K
R2 = 1 MEG
R3 = 10K
R4 = 1 MEG
R5 = 2.2K
R6 = 47K
R7 = 10K
R8 = 470 Ohm
R9 = 33K
R10 = 4.7K
R11 = 10 Ohm
R12 = 10 Ohm
R13 = 470 Ohm
R14 = 10 Ohm
R15 = 22 Ohm
RM1 = 150 Ohm
Capacitors: - Disc Or Electrolytic ( Electrolytic Shown with +/- ) All Low Voltage
C1 = .05
C2 = .001
C3 = .05
C4 = 220 MFD
C5 = .01
C6 = 100 pf
C7 = .01
C8 = 2 to 22 Pf Trimmer ( Adjustable ) Small Surface Mount Type
C9 = 2 to 22 Pf Trimmer ( Adjustable ) Small Surface Mount Type
C10 = .01
C11 = .01
C12 = 2 to 22 Pf Trimmer ( Adjustable ) Small Surface Mount Type
C13 = .001
C14 = 12 to 70 Pf Trimmer ( Adjustable ) Small Surface Mount Type
C15 = 2 to 22 Pf Trimmer ( Adjustable ) Small Surface Mount Type
Q1, Q2, and Q3 - 2N3904 - Digi-Key Electronics
Q4, Q5 2N3866 - Digi-Key Electronics
MIC: Electret Element
.Digi-key Electronics sell some very small and sensitive ones.
NTE-613 Varactor Diode or a suitable replacement such as the Digi-Key Electronics MV2107
Any, On / Off Switch Will Do - connecting the + side of the 9 volt battery to the circuit
9.0 Volts D.C. The Negative Side Of The Battery Connects To The On/Off Switch to ground
20 1/2 Tight Turns of # 30 Magnet Wire Wound tight on a Digi-key Electronics 3368K-ND Fiber Washer. The Inductance of this coil is .150 uH
L2:13 1/2 Tight Turns of # 24 Magnet Wire Wound tight on a Digi-key Electronics 3368K-ND Fiber Washer. The Inductance of this coil is .067 uH
9 Tight Turns of # 26 Magnet Wire Wound tight on a Digi-key Electronics 3368K-ND Fiber Washer
2 Turns of # 24 Magnet Wire Air Wound around a .155 Drill Bit. Width between turns = 1/8"
18 Inches of small flexible stranded wire
XT1: ( CRYSTAL )
This Circuit was a pure Accident - But The Damn thing works, and works great! It functions with virtually any crystal you insert into it. I designed this unit for a young kid on a Task Force down in Georgia, and accidently - thru a mistake - prototyped it with the wrong crystal.
I started plugging various crystals into it, tuning the unit up, and then listening to it's output on a scanner. The quality was great and you only need experiment with it.
With various Digi-Key Electronics CA-301 Barrel Crystals and several Junk Box Crystals - Here are some of the end frequencies ( Transmit ) I came up With:
50.0 Mhz Xtal = Transmitted at 166.953 Mhz. 49.8 Mhz Xtal = Transmitted at 166.430 Mhz. 55.0 Mhz Xtal = Transmitted at 165.160 Mhz. ( Junk Box Crystal - 143.7640 Mhz ) = Transmitted at 164.116 Mhz. 46.0 Mhz Xtal = Transmitted at 153.568 Mhz. 42.0 Mhz Xtal = Transmitted at 154.224 Mhz.
In All Cases, when tuned - the output was measured @ 2.5 Volts RF into a 50 Ohm Load - Or an actual RMS Output of 125 Mw