Legal FM Transmitter?

[audioguru]

I plan stripboard layout on grid-paper then cut the copper tracks to length with a drill-bit.
The copper tracks form most of the wiring and the parts and a few short jumper wires complete the wiring.

 

[kolisson]

This link works better.

SparkFun Electronics - FM Radio Transmitter Module - NS73M

klaus

 

[audioguru]

The SparkFun FM stereo transmitter module is extremely tiny. It might be impossible for a hobbiest to connect to. They say it transmitted 6 feet or 60 feet (there is a typo in their range claim).

 

[kolisson]

in fact the chip itself is very very tiny but if you buy it together with the breakout board
its quite easy to solder.

SparkFun Electronics - FM Radio Module Breakout Board - NS73M

the output power is selectable 0,5 / 1 / 2 mW.
so the range will be much more than 6feet.

but keep in mind that you will need a small microcontroller (attiny) to do the initialisation during power up (setting the desired frequency and so on).

regards klaus

 

[TheNewGuy]

in fact the chip itself is very very tiny but if you buy it together with the breakout board
its quite easy to solder.

SparkFun Electronics - FM Radio Module Breakout Board - NS73M

the output power is selectable 0,5 / 1 / 2 mW.
so the range will be much more than 6feet.

but keep in mind that you will need a small microcontroller (attiny) to do the initialisation during power up (setting the desired frequency and so on).

regards klaus

The SparkFun FM stereo transmitter module is extremely tiny. It might be impossible for a hobbiest to connect to. They say it transmitted 6 feet or 60 feet (there is a typo in their range claim).

My god that is small!

 

[TheNewGuy]

I don't know why, but all of the sudden my transmitter has stopped working. I have no idea, I've tried everything I know...

 

[Hero999]

Did any of the components get hot?

 

[mbarazeen]

Try the attached one, i made it as hobby 15 yrs before and the frequency stability was not so bad and the range was in commercial FM band. can be tuned easily.

there is a Ferdie bed transformer same as IF transformer having two windings as in the drawing. that can be varied to bring to the required frequency or the 2-10pf capacitor can change the frequency.

on eBay i have purchased tiny modules with FM stereo modulation, programmable to some discrete frequencies.

Edit: L3 is 10 turns 36 wire

 

[TheNewGuy]

R1 is a 1,000 Ω pot and R2 is a 100 Ω resistor. Would this be on the FM Band?

EDIT: None of the components got hot

 

[atferrari]

Maybe it had time to cool down.

 

[TheNewGuy]

I've done a little reaserch:

Could I get better quality if I remade my FM Transmitter and based it off of a Colpitts oscillator using the same 2N3904? I even have a collapsible antenna like in the video.

Also: is 50 MHz on the FM Band?

I found this video and was curious:

 

[TheNewGuy]

If I can get my hands on the parts, I want to do a micromitter. But for now, I'm just experimenting with the 2N3904 and 2N3906 I have.

 

[mneary]

That quality should not be difficult to duplicate

no, 50MHz is not in the US FM broadcast band. It's near the bottom edge of the 6 meter HAM band. Since hams on 6 meters like to use sensitive receivers to pick up weak signals, you would be extremely likely to annoy someone.

 

[mbarazeen]

see the circuit on my post #29, use the 2N3904 and solder it, you may get a good result.

 

[audioguru]

Also: is 50 MHz on the FM Band?

The video is probably a fake.
Simply look at the dial of an FM radio to see that its frequencies are from 88MHz to 108MHz.

 

[JimB]

The signal displayed on the scope is far from a sinewave, to mee it looks more like a triangle with rounded corners, in which case it will have a large harmonic content.
2 x 50Mhz is 100Mhz, right in the middle of the VHF FM band.

Just another poxy little half baked noise toy.

JimB

 

[audioguru]

A 'scope with a lower bandwidth will show a near-perfect sine-wave when looking at the triangle-wave..

 

[JimB]

A 'scope with a lower bandwidth will show a near-perfect sine-wave when looking at the triangle-wave..

Quite right AG, but the point I was trying to make was that while the bandwidth of the scope is unknown, it is displaying a waveform which is something between a sinewave and a triangle wave.
As it is not a sinewave, there must be harmonics in there, one of which will be in the FM broadcast band.

JimB

 

[TheNewGuy]

I can't figure out why in the world the thing wont transmit anymore!

I don't think it is the transistor, because I'm only powering the circuit (the one in my original post) with a 9V battery. Also, it never got hot enough to burn out (I think).

Something tells me that the value of the resistors are creating a frequency off the FM Band or I have something backwards...should I get out my camera and take pictures? My reasoning is that if something burnt out, it would at least make some noise on the radio I'm not getting anything.

 

[TheNewGuy]

Try the attached one, i made it as hobby 15 yrs before and the frequency stability was not so bad and the range was in commercial FM band. can be tuned easily.

there is a Ferdie bed transformer same as IF transformer having two windings as in the drawing. that can be varied to bring to the required frequency or the 2-10pf capacitor can change the frequency.

on eBay i have purchased tiny modules with FM stereo modulation, programmable to some discrete frequencies.

Edit: L3 is 10 turns 36 wire

This circuit looks cool, if I get the parts for it I'll build it. The reason why I built the one in the OP is because I had the parts.