Please help me find a good FM transmitter schematic

rrrremus · 2nd September 2010, 07:38 AM

Hello everyone. I searched the nets but did not find anything that fits my needs.
I need to build myself an stable stereo FM transmitter that is capable of delivering good audio quality in the 87-108 Band and digital controlled + LCD.
I have a few schematics of such devices but they are mostly old designs and i cannot find specific ICs anymore.
Power is not important since i have a 100W linear RF amp at my disposal.
Thank you.

Speedskater · 2nd September 2010, 03:33 PM

Transmitter kits are available from a US company Ramsey Electronics:
Ramsey Electronics

Many decades ago when I was in radio broadcast engineering a guy built a FM transmitter using Sam's Books training books. So he built a unit that was identical to the exciter in our transmitter. Late one night we connected it to our 5000W transmitter and it worked great!

bob91343 · 2nd September 2010, 04:32 PM

Years ago I built a stereo multiplex generator, solid state, that worked fine. It used a 19 kHz crystal. It's a simple matter to use the output of such a unit to modulate an oscillator and achieve FM suitable for radiation.

One thing to do is make sure you are not violating any rules, regulations, or laws concerning building and using a transmitter. Here in the US there are limits on how much power is to be used without a license. And with a license, equipment must be type approved (or type accepted, not sure).

jpr_pt · 2nd September 2010, 04:36 PM

Take a look at North Country Radio Home Page

wakibaki · 05:16 PM

There are a lot of these available off-the-shelf for sending your MP3 player or WHY to your car radio.

Far be it from me to discourage anybody from building a transmitter, but the cost is trivial from e.g. DealExtreme: Cool Gadgets at the Right Price - Site-Wide Free Shipping - DX, you could just bust it open, they come with LCD frequency displays and remotes in some cases.

You may have a hundred watt linear amplifier available, but be aware that putting out anything more than a very small amount of power (50 nanowatts in the EU) is strictly illegal in just about every jurisdiction worldwide.

w

gmphadte · 7th September 2010, 10:42 AM

Bh1417

rrrremus · 25th September 2010, 08:52 AM

Thank you all. I will try not to violate any laws. The power output can be controlled. I will just need good signal in the range of 100 meters.

2nd September 2010, 07:38 AM	#1
rrrremus diyAudio Member Join Date: Sep 2009 Location: Timisoara	Please help me find a good FM transmitter schematic Hello everyone. I searched the nets but did not find anything that fits my needs. I need to build myself an stable stereo FM transmitter that is capable of delivering good audio quality in the 87-108 Band and digital controlled + LCD. I have a few schematics of such devices but they are mostly old designs and i cannot find specific ICs anymore. Power is not important since i have a 100W linear RF amp at my disposal. Thank you.

2nd September 2010, 03:33 PM	#2
Speedskater diyAudio Member Join Date: Sep 2002 Location: Lakewood, Ohio	Transmitter kits are available from a US company Ramsey Electronics: Ramsey Electronics Many decades ago when I was in radio broadcast engineering a guy built a FM transmitter using Sam's Books training books. So he built a unit that was identical to the exciter in our transmitter. Late one night we connected it to our 5000W transmitter and it worked great! __________________ Kevin

2nd September 2010, 05:13 PM	#5
wakibaki Banned Join Date: Jan 2008 Blog Entries: 2	There are a lot of these available off-the-shelf for sending your MP3 player or WHY to your car radio. Far be it from me to discourage anybody from building a transmitter, but the cost is trivial from e.g. DealExtreme: Cool Gadgets at the Right Price - Site-Wide Free Shipping - DX, you could just bust it open, they come with LCD frequency displays and remotes in some cases. You may have a hundred watt linear amplifier available, but be aware that putting out anything more than a very small amount of power (50 nanowatts in the EU) is strictly illegal in just about every jurisdiction worldwide. w Last edited by wakibaki; 2nd September 2010 at 05:16 PM.

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2nd September 2010, 04:32 PM	#3
bob91343 diyAudio Member Join Date: Mar 2010	Years ago I built a stereo multiplex generator, solid state, that worked fine. It used a 19 kHz crystal. It's a simple matter to use the output of such a unit to modulate an oscillator and achieve FM suitable for radiation. One thing to do is make sure you are not violating any rules, regulations, or laws concerning building and using a transmitter. Here in the US there are limits on how much power is to be used without a license. And with a license, equipment must be type approved (or type accepted, not sure).

2nd September 2010, 04:36 PM	#4
jpr_pt diyAudio Member Join Date: Dec 2008	Take a look at North Country Radio Home Page

7th September 2010, 10:42 AM	#6
gmphadte diyAudio Member Join Date: Jul 2003 Location: Dona paula, Goa	Bh1417

25th September 2010, 08:52 AM	#7
rrrremus diyAudio Member Join Date: Sep 2009 Location: Timisoara	Thank you all. I will try not to violate any laws. The power output can be controlled. I will just need good signal in the range of 100 meters.

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