Some More Simple FM Transmitters - Page 4 - Electronic Circuits Projects Diagrams Free

GreenAce92 · 14th November 2007, 01:31 AM

What about the 72mhz transmitters? I just need to know how to make a simple transmitter + receiver which i can then plant into an rc vehicle. This is jsut to learn and its not for long. I am buying a real transmitter system but i just want to learn how it works and how to build one and modify to do what i want to do.

Any help would be appreciated.
Thanks.

audioguru · 14th November 2007, 01:59 AM

A simple transmitter and receiver are junk.

delta06 · 28th November 2007, 09:33 AM

Thanks audioguru, your transmitter will make a good project...

hariswj · 29th December 2007, 01:42 AM

Audioguru,
Do you have a coilless 27 Hhz AM transmitter schematic, I mean with X-tal. My experience, I have that schematic that was very simple but I lost it. My current project is building a 27 Hmz walkie talkie. Can you help me?
Thank's.

harries

audioguru · 29th December 2007, 01:57 AM

Every transmitter that I have ever seen except one, uses coils and capacitors in a tuned circuit to reduce harmonics that cause interference at other frequencies. The one that doesn't use a coil operates from the 9th harmonic of a 10.7MHz ceramic filter. It is very low power so its other harmonics don't cause too much interference.
Transmitters with a crystal also use a tuned circuit with a coil.

I just looked in Google for Walkie Talkie Circuits and found a few. It even had a link to a thread here about walkie talkie circuits.

hariswj · 29th December 2007, 02:38 AM

Audioguru,
I spent alo of times in Google for that, but not found yet. Ok now I understand that. Actually, I have a walkie talkie schematic attached. Receiver and oscilator coils are from 0,5mm on oscilator coil 8mm with 9 turns. RFC is from 0,5mm on 0.5cm free air coil with 33 turns.

my problems are :
1. I don't have a 27Mhz signal generator to tune that circuit. Can you help me?
2. The sound modulation is very low. How to solve this problem?
3. How to increase the distance?
Thank's for help.

audioguru · 29th December 2007, 03:12 AM

Your walkie talkie doesn't work well because it is cheap.
Its parts cost about $2.00. It cannot be tuned.

The schematic has an error: The collector of Q1 is supposed to connect to something with negative DC on it.

hariswj · 6th January 2008, 08:39 AM

Dear Audiguru,

I would like to build your FM Transmitter, but I have the dificulties to find transistor 2N3904 in my town. I would like to substitute Q1 with C829 for preamp mic, Q2 with C930 and Q3 with C930 or C1970. Is it possible to do?
Thank's

Hero999 · 6th January 2008, 11:51 AM

Try the 2N2222A, those transistors you suggested sound really old.

audioguru · 6th January 2008, 04:16 PM

The 2N3904 transistor is extremely common. Maybe it is not available in the Orient. A BC547 is almost the same but its pins are reversed.

The old Yapanese transistors are completely different.
The max allowed collector current for the 2SC930 is only 30mA.
The 2SC1970 power transistor has a huge range of hFE from 10 to 180 and its capacitance is too high.

hariswj · 6th January 2008, 11:48 PM

2N2222 sounds common for me. I'll try to find it. And is it possible to modify it as a PLL Transmitter with the PLL module from http://www.pira.cz/enpll.htm? How to connect it inside your Transmitter?
Thank's for help.

audioguru · 7th January 2008, 03:42 PM

My FM transmitter does not have a voltage-controlled oscillator. Usually they use a varactor diode which is tuned with the output voltage from the PLL circuit.

Why don't you make a kit or make your own Micromitter? It has a quartz crystal and a PLL and it is stereo.
http://electronics-diy.com/schematic...ransmitter.htm

tytower · 7th January 2008, 09:08 PM

Older thread -newer question

How long is the red wire antenna on your transmitter audioguru?f
From the point of attachment to the board.

Have you experimented at all with a very fine wire which will tend to sharpen the bandwith

audioguru · 7th January 2008, 09:20 PM

Quote:

Originally Posted by tytower

How long is the red wire antenna on your transmitter audioguru?f
From the point of attachment to the board.

I tried it with a quarter-wave length. 80cm.

Quote:

Have you experimented at all with a very fine wire which will tend to sharpen the bandwith

The tuned circuits and the amplitude of the modulation determine the bandwidth, not the wire gauge of the antenna.

tytower · 9th January 2008, 09:18 PM

Quote:

Originally Posted by audioguru

The tuned circuits and the amplitude of the modulation determine the bandwidth, not the wire gauge of the antenna.

I take it you are not a radio ham?
Wire cross -section of the antenna is quite a factor at HF

14th November 2007, 01:59 AM	(permalink)
audioguru Experienced Member	A simple transmitter and receiver are junk. __________________ Uncle $crooge

29th December 2007, 01:57 AM	(permalink)
audioguru Experienced Member	Every transmitter that I have ever seen except one, uses coils and capacitors in a tuned circuit to reduce harmonics that cause interference at other frequencies. The one that doesn't use a coil operates from the 9th harmonic of a 10.7MHz ceramic filter. It is very low power so its other harmonics don't cause too much interference. Transmitters with a crystal also use a tuned circuit with a coil. I just looked in Google for Walkie Talkie Circuits and found a few. It even had a link to a thread here about walkie talkie circuits. __________________ Uncle $crooge

29th December 2007, 03:12 AM	(permalink)
audioguru Experienced Member	Your walkie talkie doesn't work well because it is cheap. Its parts cost about $2.00. It cannot be tuned. The schematic has an error: The collector of Q1 is supposed to connect to something with negative DC on it. __________________ Uncle $crooge

6th January 2008, 11:51 AM	(permalink)
Hero999 Experienced Member	Try the 2N2222A, those transistors you suggested sound really old. __________________ What's so bad about Microsoft? Get Opera it's simply a superb browser.

6th January 2008, 04:16 PM	(permalink)
audioguru Experienced Member	The 2N3904 transistor is extremely common. Maybe it is not available in the Orient. A BC547 is almost the same but its pins are reversed. The old Yapanese transistors are completely different. The max allowed collector current for the 2SC930 is only 30mA. The 2SC1970 power transistor has a huge range of hFE from 10 to 180 and its capacitance is too high. __________________ Uncle $crooge

14th November 2007, 01:31 AM	(permalink)
GreenAce92 New Member	What about the 72mhz transmitters? I just need to know how to make a simple transmitter + receiver which i can then plant into an rc vehicle. This is jsut to learn and its not for long. I am buying a real transmitter system but i just want to learn how it works and how to build one and modify to do what i want to do. Any help would be appreciated. Thanks.

28th November 2007, 09:33 AM	(permalink)
delta06 New Member	Thanks audioguru, your transmitter will make a good project...

29th December 2007, 01:42 AM	(permalink)
hariswj New Member	Audioguru, Do you have a coilless 27 Hhz AM transmitter schematic, I mean with X-tal. My experience, I have that schematic that was very simple but I lost it. My current project is building a 27 Hmz walkie talkie. Can you help me? Thank's. harries

6th January 2008, 08:39 AM	(permalink)
hariswj New Member	Dear Audiguru, I would like to build your FM Transmitter, but I have the dificulties to find transistor 2N3904 in my town. I would like to substitute Q1 with C829 for preamp mic, Q2 with C930 and Q3 with C930 or C1970. Is it possible to do? Thank's

6th January 2008, 11:48 PM	(permalink)
hariswj New Member	2N2222 sounds common for me. I'll try to find it. And is it possible to modify it as a PLL Transmitter with the PLL module from http://www.pira.cz/enpll.htm? How to connect it inside your Transmitter? Thank's for help.

7th January 2008, 03:42 PM	(permalink)
audioguru Experienced Member	My FM transmitter does not have a voltage-controlled oscillator. Usually they use a varactor diode which is tuned with the output voltage from the PLL circuit. Why don't you make a kit or make your own Micromitter? It has a quartz crystal and a PLL and it is stereo. http://electronics-diy.com/schematic...ransmitter.htm __________________ Uncle $crooge

7th January 2008, 09:08 PM	(permalink)
tytower Experienced Member	Older thread -newer question How long is the red wire antenna on your transmitter audioguru?f From the point of attachment to the board. Have you experimented at all with a very fine wire which will tend to sharpen the bandwith __________________ I Hate Microsoft-the site below says it well http://www.vanwensveen.nl/rants/micr...eMS_intro.html

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