Some More Simple FM Transmitters - Page 3 - Electronic Circuits Projects Diagrams Free

Hero999 · 31st August 2007, 08:20 PM

Look up FM on Wikipedia.

AND_ECE · 15th September 2007, 06:45 AM

Quote:

Originally Posted by audioguru

Mine has a power amp stage and goes very far:

its that really working and what bout the range of that fm transmitter? an you explain the circuit to me.. so that i can understand thanks

audioguru · 19th September 2007, 12:19 AM

My FM transmitter has an RF amplifier on its output.
With a new 9V alkaline battery its range is more than 2km across a large river valley to my very sensitive home FM tuner and to my very sensitive car radio.
The range is about 300m to my Sony Walkman radio.

Hills, buildings and trees block the signal.

HiTech · 20th September 2007, 07:51 PM

I think I heard your broadcast of Gordon Lightfoot's song, The Edmund Fitzgerald. The transmission must have rode in on one of those Great Lakes gales that begin this time of year!!

BTW, sometime I want to discuss these Alberta Clippers that you folks send our way. That stuff has got to stop or we start sending you illegal Mexicans .... (and we have enough of them to cripple your economy!

audioguru · 20th September 2007, 08:06 PM

Canada gets its share of illegal foreigners. They do the "dirty" work that local people don't want to do. Boatloads arrive from China each year.

TinaiKevin · 30th October 2007, 08:31 AM

Does anyone have a circuit of a simple low power FM transmitter that uses crystal 1MHz and has a 105Mhz output? dont know how that is done but if anyone can help??

**Nigel Goodwin** · 30th October 2007, 10:01 AM

Trouble is it wouldn't be simple!.

TinaiKevin · 30th October 2007, 10:31 AM

You are right about it being not simple! Is there any other alternative to the programmable chip, by using dividers/multipliers(that are set) or flipflops. I am not that well versed with all programmable stuff.

Thanks

**Nigel Goodwin** · 30th October 2007, 11:03 AM

Quote:

Originally Posted by TinaiKevin

You are right about it being not simple! Is there any other alternative to the programmable chip, by using dividers/multipliers(that are set) or flipflops. I am not that well versed with all programmable stuff.

No, from a 1MHz crystal you have to use a PLL system, you couldn't even use multipliers - which would be complicated anyway.

mvs sarma · 30th October 2007, 01:49 PM

If you can use 15MHz crystal as oscillator and derive the 7th harmonic, perhps you may end up getting the required 105MHz. Mostly a single 74HCU04 and few pf caps and an inductor are all that are needed. It could work off 5Vsupply. A sample diagram is attached , thanks to G Baars the designer of SW radio capture.

audioguru · 30th October 2007, 03:25 PM

There is a similar FM transmitter that uses a 10.7Mhz crystal filter from the IF of an FM radio as its oscillator. Then Cmos inverters clip it into aquare-waves and its output at the 9th harmonic is at 96.3MHz.

I don't think an ordinary CD4069 inverter works at a frequency as high as 10.7MHz. Maybe a 74HC04 is needed with a 5V supply.

mvs sarma · 30th October 2007, 04:41 PM

I fear there is no filter that would select 9th harmonic, as such, we cant, say it would not interfere at many other frequencies.-- in the FM band
it will be seen as 9th harmonic -may be. the actualtransmitted energu may be perhaps 10.& only.
as 4069 is working with a 9V supply, it might cover upto 10 or 12 MHz

audioguru · 30th October 2007, 06:11 PM

Quote:

Originally Posted by mvs sarma

I fear there is no filter that would select 9th harmonic, as such, we cant, say it would not interfere at many other frequencies.-- in the FM band

It has a square-wave output so its even harmonics are low.
It has very low output power so it won't cause much interference.
Its higher harmonics are low level and might be on a TV channel's frequency.
Its 7th harmonic at 74.9MHz is not in the FM band but might be a TV channel in some countries.

GreenAce92 · 13th November 2007, 10:58 PM

Are those transmitters the same as the ones located in rc stuff like cars and stuff? Could anyone tell me the requirments to make one of these that can control motors for at least 20 ft?

audioguru · 13th November 2007, 11:53 PM

Quote:

Originally Posted by GreenAce92

Are those transmitters the same as the ones located in rc stuff like cars and stuff? Could anyone tell me the requirments to make one of these that can control motors for at least 20 ft?

These are wideband FM transmitters for the FM broadcast band.

Cheap RC transmitters are just a single transistor that has AM modulation and a single transistor "radio receiver" that is a super-regen receiver.

Good RC transmitters and receivers use a quartz crystal for frequency accuracy and many transistors and ICs for digital FM.

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31st August 2007, 08:20 PM	(permalink)
Hero999	Look up FM on Wikipedia. __________________ What's so bad about Microsoft? Get Opera it's simply a superb browser.

19th September 2007, 12:19 AM	(permalink)
audioguru	My FM transmitter has an RF amplifier on its output. With a new 9V alkaline battery its range is more than 2km across a large river valley to my very sensitive home FM tuner and to my very sensitive car radio. The range is about 300m to my Sony Walkman radio. Hills, buildings and trees block the signal. __________________ Uncle $crooge

20th September 2007, 07:51 PM	(permalink)
HiTech	I think I heard your broadcast of Gordon Lightfoot's song, The Edmund Fitzgerald. The transmission must have rode in on one of those Great Lakes gales that begin this time of year!! BTW, sometime I want to discuss these Alberta Clippers that you folks send our way. That stuff has got to stop or we start sending you illegal Mexicans .... (and we have enough of them to cripple your economy! __________________ Don't make me reach through this monitor to slap you a good one! Last edited by HiTech; 20th September 2007 at 07:54 PM.

20th September 2007, 08:06 PM	(permalink)
audioguru	Canada gets its share of illegal foreigners. They do the "dirty" work that local people don't want to do. Boatloads arrive from China each year. __________________ Uncle $crooge

30th October 2007, 08:31 AM	(permalink)
TinaiKevin	Does anyone have a circuit of a simple low power FM transmitter that uses crystal 1MHz and has a 105Mhz output? dont know how that is done but if anyone can help??

30th October 2007, 10:01 AM	(permalink)
Nigel Goodwin	Trouble is it wouldn't be simple!. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

30th October 2007, 10:31 AM	(permalink)
TinaiKevin	FM transmitter You are right about it being not simple! Is there any other alternative to the programmable chip, by using dividers/multipliers(that are set) or flipflops. I am not that well versed with all programmable stuff. Thanks

30th October 2007, 01:49 PM	(permalink)
mvs sarma	If you can use 15MHz crystal as oscillator and derive the 7th harmonic, perhps you may end up getting the required 105MHz. Mostly a single 74HCU04 and few pf caps and an inductor are all that are needed. It could work off 5Vsupply. A sample diagram is attached , thanks to G Baars the designer of SW radio capture. __________________ Regards, Sarma. Last edited by mvs sarma; 7th July 2008 at 12:14 PM.

30th October 2007, 04:41 PM	(permalink)
mvs sarma	I fear there is no filter that would select 9th harmonic, as such, we cant, say it would not interfere at many other frequencies.-- in the FM band it will be seen as 9th harmonic -may be. the actualtransmitted energu may be perhaps 10.& only. as 4069 is working with a 9V supply, it might cover upto 10 or 12 MHz __________________ Regards, Sarma.

13th November 2007, 10:58 PM	(permalink)
GreenAce92	Are those transmitters the same as the ones located in rc stuff like cars and stuff? Could anyone tell me the requirments to make one of these that can control motors for at least 20 ft?