L4 20 tight turns # 26 Magnet wire – Same Form Digi-key Electronics 3368K-ND

18 1/2 Inches of small flexible stranded wire

I normally build this circuit using a Digi-Key Electronics Barrel Crystal (CA-301), 15 Mhz for a standard output frequency of 150.00 Mhz. If you want to customize the frequency, follow the directions below.

I usually build this circuit to operate between 150 to 165 Mhz. The Crystals I use Are The Digi-Key Electronics Barrel Crystals CA-301 Type which cost a couple of bucks per crystal. This circuit uses a X5 Multiplier and then a X2 Multiplier In the Final.

Example: If I use a 15 Mhz Barrel Crystal, the frequency at Q4s output is: Xtal X 5 Or: 75 Mhz into Q5. Q5 Multiplies 75 Mhz X 2 for an end frequency out of the final Q6 ( Desired Output Frequency ) of 150.00 Mhz.

Virtually any Fundamental Crystal between 14 and 17 Mhz will output a frequency of between 140 to 170 Mhz, if the crystal has a load capacitance of around 18 pf. If you wish to build this transmitter on A custom frequency simply use the X5 X2 formula below and order a custom cut crystal specifying an 18 pf CL.

Example: My Customer Desires this transmitter to function at an output frequency of: 158.250 Mhz?
( 1 ) Divide 158.250 times 2. This Equals 79.125
( 2 ) Divide 79.125 times 5. This Equals 15.825
I would order the crystal at a Fundamental frequency of 15.825 Mhz, tolerance of .001% and a Crystal Load Capacitance of 18 pf. When I tune my transmitter, my output transmit frequency would be: 158.250 Mhz.


Return To Our Home Page

5VT - 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,  primarly 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
 FM Transmitter Schematic  5VT


(C) 2012  radio-circuits .com
The 5VT Transmitter uses a small 1.5 V "N" battery or can use a hearing aid battery if you surface mount the device rather than use a "Thru-The-Hole" configuration. Operational in the upper VHF Band. Transmits both sides of the conversation. Low powered and can be used with a repeater. Some of the companies that I have farmed this design out to incorporate it into a pen using surface mount rather than thru the hole.

5VT - 1.5V Transmitter
2011 By John S. Wilson Jr

Parts List: Circuit # 5VT – “MicroBug” - Xtal Controlled

Resistors: 1/4 Watt – This unit can go with smaller values and also surface mount.

R1 = 2.2K
R2 = 1 MEG
R3 = 10K
R4 = 1 MEG
R5 = 100K
R6 = 470K
R7 = 22K
R8 = 10K pot or SMD for adjusting deviation
R9 = 10K
R10 = 470 Ohm
R11 = 33K
R12 = 4.7K
R13 = 100 Ohm
R14 = 10K
R15 = 220 Ohm

Capacitors: - Disc Or Electrolytic ( Electrolytic Shown with +/- )  All Low Voltage
C1 = .01
C2 = .001
C3 =  470 pf
C4 =  .01
C5 =  .01
C6 = 100 pf
C7 =  .001
C8 =  2.5 to 20 pf Trimmer ( Adjustable ) Small Surface Mount Type.
C9 =  10 pf
C10 = .1
C11 =  .001
C12 =  2.5 to 20 pf Trimmer ( Adjustable ) Small Surface Mount Type.
C13 =  10 pf
C14 = 18 pf
C15 =  .01
C16 =  .001
C17 = 2.5 to 20 pf Trimmer ( Adjustable ) Small Surface Mount Type.
C18 = 47 pf
C19 = 2.5 to 20 pf Trimmer ( Adjustable ) Small Surface Mount Type.

Q1, Q2, Q3 and Q4 = PN3904 NPN - Digi-key Electronics
Q5, Q6 and Q7 = BFS17 - Digi-key Electronics

NTE-613 Varactor Diode or a suitable replacement like the ( MV2107 - Digi-Key Electronics )

ON/OFF Switch:
Any, On / Off Switch Will Do - connecting the + side of the 1.5 volt battery to the circuit

1.5 Volts D.C.

Small Electret Microphone Element. Digi-key Electronics

L1, L2 and L3
Form: Digi-key Electronics Part Number 3368K-ND Fiber Washer.
8 spaced turns # 26 Magnet wire