FM Transmitter

Author	Views	Views Today	Rank	Comments
	518,363	236		379

Here is the schematic, PC board pattern, and parts placement for a low powered FM transmitter. The range of the transmitter when running at 9V is about 300 feet. Running it from 12V increases the range to about 400 feet. This transmitter should not be used as a room or telephone bug.

Schematic

PC Board Layout and Parts Placement

Parts

Part	Total Qty.	Description	Substitutions
C1	1	0.001uf Disc Capacitor
C2	1	5.6pf Disc Capacitor
C3,C4	2	10uf Electrolytic Capacitor
C5	1	3-18pf Adjustable Cap
R1	1	270 Ohm 1/8W Resistor	270 Ohm 1/4W Resistor
R2,R5,R6	3	4.7k 1/8W Resistor	4.7K 1/4W Resistor
R3	1	10k 1/8W Resistor	10K 1/4W Resistor
R4	1	100k 1/8W Resistor	100K 1/4W Resistor
Q1, Q2	2	2N2222A NPN Transistor	2N3904, NTE123A
L1, L2	2	5 Turn Air Core Coil
MIC	1	Electret Microphone
MISC	1	9V Battery Snap, PC Board, Wire For Antenna

Notes

L1 and L2 are 5 turns of 28 AWG enamel coated magnet wire wound with a inside diameter of about 4mm. The inside of a ballpoint pen works well (the plastic tube that holds the ink). Remove the form after winding then install the coil on the circuit board, being careful not to bend it.

C5 is used for tuning. This transmitter operates on the normal broadcast frequencies (88-108MHz).

Q1 and Q2 can also be 2N3904 or something similar.

You can use 1/4 W resistors mounted vertically instead of 1/8 W resistors.

You may want to bypass the battery with a .01uf capacitor.

An antenna may not be required for operation.

A thanks goes out to Mike_Springer@iname.com for cleaning up the original image once displayed on the page. It looks a lot better now!

Related Circuits

Comments

Add A Comment

RAHUL FM Transmitter Wednesday, August 18, 2010 8:09:30 AM

HEY WORKING REALLY GOOD...!! BUT HAS VERY SHORT RANGE... FOR THOSE WHO ARE HAVING PROBLEM ... REGARDING INDUCTOR: 1.BUY ENAMEL COATED MAGNETIC WIRE TO BUILD INDUCTOR. 2. CUT WIRE INTO TWO PIECES : 8cm EACH. REMOVE ENAMEL COATING FROM BOTH ENDS OF WIRES.& CHECK THE CONTINUITY 3. TAKE A PEN REFILL (LEXI,CELLO ,TECHNO TIP.ETC ) WHICH HAS OUTER DIAMETER OF 3.2mm approx. 4. WIND WIRE ON REFILL (5 TURNS). 5. DONT BEND WIRE WHILE WINDING, REGARDING CAPACITOR: 1. IF YOU DONT HAVE VAR. CAPACITOR THEN CONNECT ANY FIXED CAPACITOR (disk) BETWEEN RANGE OF 3-18pf. REGARDING ANTENNA: 1.YOU CAN CONNECT SIMPLE WIRE ALSO. REGARDING RECEIVER. 1, IT WORKS VERY..WELL WITH CELL PHONE RADIO RECEIVER DUE TO HIGH SELECTIVITY.( VERY CLEAR.) TUNE IT IN AUTOMATIC MODE. 2.WORKS VERY VERY POOR WITH TRAD. RADIO RECEIVERS. REGARDING TRANSISTOR: ...I USED 2N2222A . DRAWBACK: 1.SHORT RANGE. BEST SOLUTION: 1.BUY LESS TOLERENCE COMPONENTS. FOR MORE COVERAGE.. 1. PUT POWER AMPLIFIER BEFORE ANTENNA. (FOR POWER AMPL. .....SEARCH ON GOOGLE ).

anonymous FM Transmitter Wednesday, June 16, 2010 11:14:01 PM

For those asking to further the range. You can easily amplify the signal, but after grabing a certain distance the fcc will get on your tail.

fm TRASCE FM Transmitter Thursday, June 10, 2010 2:47:38 AM

DOES NOT WORK!!!! i have put 18 AWG coils! What to do!

anonymous FM Transmitter Thursday, June 03, 2010 11:38:36 PM

Im a thirteen year old and i want to build 1

anonymous FM Transmitter Monday, May 24, 2010 12:45:07 PM

Is their anyway to test the circuit without having to search through every radio frequency? A fast reply would be greatly appreciated.

anonymous bbn Thursday, May 13, 2010 4:10:56 AM

i try 1.3watt fm transmitter amplifier with 2sc1970 & c2053 its the best .... check google search

anonymousnerd FM Transmitter Tuesday, April 13, 2010 5:38:03 PM

Hi, My brother and I are planing to make two for a intercom, is this to powerful for indoor use? Or is it just that you do not want people using it as a bug? Thanks a lot, AnonymousNerd

K FM Transmitter Tuesday, April 13, 2010 7:58:13 AM

I am not an enginer, I do not know how to build a transmitter but I need someone who can get me one. Thank you.

Genesis FM Transmitter Monday, March 29, 2010 3:16:57 PM

How can i produce a desired frequency?? What parameters should i change to get a lower frequency radio wave?

amor FM Transmitter Wednesday, March 24, 2010 4:28:42 AM

what is the substitute for 3-18pf adjustable cap??

The last 10 comments are currently shown. Show All Comments. Add A Comment

If you would like to leave a comment, you can do so using the form below. Comments can be things like suggestions, successes or failures, improvements, similar circuits, error reports, an answer to a previous commenter's question, or anything in between. However if you would like to ask a question it is suggested that you use the forum instead. The forum provides a more robust environment for discussion.

Important: If you post a technical question here, there is no guarantee it will be answered. All technical questions should be posted to the forum. The owner of this site generally does not answer questions in comments.

All comments are subject to approval before they are displayed here, so your comment will not appear immediately. This is done mainly to prevent spam and other abuse. If you wish to remain anonymous, simply enter "anonymous" for your name and/or email.

Name:
Email:
Subject:
Comments:
Anti Spam Code:	Please enter the exact text shown in the image above into the box below. Browser cookies must be enabled to comment on circuits.

Privacy Policy

RAHUL	FM Transmitter	Wednesday, August 18, 2010 8:09:30 AM
HEY WORKING REALLY GOOD...!! BUT HAS VERY SHORT RANGE... FOR THOSE WHO ARE HAVING PROBLEM ... REGARDING INDUCTOR: 1.BUY ENAMEL COATED MAGNETIC WIRE TO BUILD INDUCTOR. 2. CUT WIRE INTO TWO PIECES : 8cm EACH. REMOVE ENAMEL COATING FROM BOTH ENDS OF WIRES.& CHECK THE CONTINUITY 3. TAKE A PEN REFILL (LEXI,CELLO ,TECHNO TIP.ETC ) WHICH HAS OUTER DIAMETER OF 3.2mm approx. 4. WIND WIRE ON REFILL (5 TURNS). 5. DONT BEND WIRE WHILE WINDING, REGARDING CAPACITOR: 1. IF YOU DONT HAVE VAR. CAPACITOR THEN CONNECT ANY FIXED CAPACITOR (disk) BETWEEN RANGE OF 3-18pf. REGARDING ANTENNA: 1.YOU CAN CONNECT SIMPLE WIRE ALSO. REGARDING RECEIVER. 1, IT WORKS VERY..WELL WITH CELL PHONE RADIO RECEIVER DUE TO HIGH SELECTIVITY.( VERY CLEAR.) TUNE IT IN AUTOMATIC MODE. 2.WORKS VERY VERY POOR WITH TRAD. RADIO RECEIVERS. REGARDING TRANSISTOR: ...I USED 2N2222A . DRAWBACK: 1.SHORT RANGE. BEST SOLUTION: 1.BUY LESS TOLERENCE COMPONENTS. FOR MORE COVERAGE.. 1. PUT POWER AMPLIFIER BEFORE ANTENNA. (FOR POWER AMPL. .....SEARCH ON GOOGLE ).
anonymous	FM Transmitter	Wednesday, June 16, 2010 11:14:01 PM
For those asking to further the range. You can easily amplify the signal, but after grabing a certain distance the fcc will get on your tail.
fm TRASCE	FM Transmitter	Thursday, June 10, 2010 2:47:38 AM
DOES NOT WORK!!!! i have put 18 AWG coils! What to do!
anonymous	FM Transmitter	Thursday, June 03, 2010 11:38:36 PM
Im a thirteen year old and i want to build 1
anonymous	FM Transmitter	Monday, May 24, 2010 12:45:07 PM
Is their anyway to test the circuit without having to search through every radio frequency? A fast reply would be greatly appreciated.
anonymous	bbn	Thursday, May 13, 2010 4:10:56 AM
i try 1.3watt fm transmitter amplifier with 2sc1970 & c2053 its the best .... check google search
anonymousnerd	FM Transmitter	Tuesday, April 13, 2010 5:38:03 PM
Hi, My brother and I are planing to make two for a intercom, is this to powerful for indoor use? Or is it just that you do not want people using it as a bug? Thanks a lot, AnonymousNerd
K	FM Transmitter	Tuesday, April 13, 2010 7:58:13 AM
I am not an enginer, I do not know how to build a transmitter but I need someone who can get me one. Thank you.
Genesis	FM Transmitter	Monday, March 29, 2010 3:16:57 PM
How can i produce a desired frequency?? What parameters should i change to get a lower frequency radio wave?
amor	FM Transmitter	Wednesday, March 24, 2010 4:28:42 AM
what is the substitute for 3-18pf adjustable cap??