+R Vass Yes. And very short as well.

+R Vass I agree for sure!

+R Vass Really..The Best

Real world application is the only way I can learn. I pay attention and take notes during lectures, but seeing something in practice is just way easier for me. Thank god for youtubers.

yay I'm glad at least one person built it

@@Afrotechmods Yup, I built the AM transmitter too. One question if I may- could a novice design the PC board for the FM transmitter, just being careful to keep leads short and use a ground plane? Or were there other considerations necessary to avoid parasitics? Thanks again for a great channel.

It already sounds like you know enough to know what you are doing with the PCB so go for it

@@Afrotechmods Thanks again!

Yay! I am glad more people are making it.

+Vayun Biyani Thank you!

+h82sk8 simple is better

Thank you! I'm glad at least one person got it!

Hehe, I'm old enough to know what it was as well. Very nice touch.

okay. I just noticed a swer is already available here

+heckleru2 It's linked in the video description section...

+Afrotechmods Thanks! I should have clicked "show more" and looked there first.

+James Brindle Yeah you'll be fine as long as you aren't trying to be a prankster

I think he has added an aux input in the photo. He mentioned that he broke out the Tune pin for this purpose, and that the aux input has to be AC coupled and about 1mv.

For those who don't know, monoaural FM can be received by AM receivers by tuning them to a frequency that's slightly too high or low. For more advanced reception, run the antenna signal (preferably preamplified) into a bandpass filter for your range, then run that into a transistor. Choose another leg of the transistor to be the output, and run a _new_ frequency into the third leg: this is produced by the "local oscillator", and causes the transistor's output to be determined by the following formula: output frequencies = [ input frequency, local oscillator frequency, input frequency - local oscillator frequency, input frequency + local oscillator frequency ], for a total of four output frequencies from two inputs. Then you run the output through another filter to remove the frequencies you don't want (hint: what you DO want is input frequency - local oscillator frequency), and finally run the result into a decode module, which can be the diode stage from a crystal AM receiver (just as an example). Tuning is achieved by changing the local oscillator's frequency. There are caveats: if ( input freq - local osc freq ) is negative, then it will actually show up as ( local osc freq - input freq ), which can cause multiple stations to tune in at the same time, thereby necessitating an intermediate filter. A fairly sensible way to achieve this is to use multiple stages of this frequency mixing: the first will move the entire range of frequencies to a lower range (because filters work more sharply for lower frequencies), where the majority of the bandwidth will be filtered out (this can be achieved by either tuning the filter, or having a fixed filter and tuning the local oscillator so that the input frequencies you want to keep are placed into the pass band), and then using the frequency mixing trick again to get the isolated frequency down to the range that you want it in. Honestly, I'd suggest 3 frequency mixers, with the first and third, as well as all of the filters, being fixed, and actual tuning being obtained by using the 2nd frequency mixer to move the desired signal into the pass-band of your "channel select" filter. This allows the variable frequency element to be restricted to a single element (the second of 3 mixers), reducing both complexity and cost, and also allows you to obtain multiple elements from a single "channel" by duplicating the 3rd mixer (with a slightly changed frequency, and possibly filter characteristics) for each additional element that you want to obtain from the "channel": FM radio in the US commonly has at least 4 (2 audio for stereo, though the encoding is a bit more complex than just two audio tracks; a plain fixed frequency for stereo detection; and a digital text signal to provide things like song title and alternative station frequencies).

What for?

Use colpitts oscillator with varactor diodes...It'll be your VCO, rest is simple.

Well you know you could use a capacitor that drains in it's own loop and just use the voltage from that to control a BJT transistor with a high enough current rating

Is there any schematic you have? because i want to build it my own ;)

Hi Thanks for the interest. I done this many years ago when sketching circuits in the back of my high school books. Basically an inductor between B and C on a biased NPN bipolar creating a tank circuit. Oscillated at 100Mhz. Supply lead inductance may also have played a role since I wasn't particularly careful about such things :-) I'll have a play and if I re-create it, i'll let you know.

Were you able to recreate it? ;)

Hi. I have re-created the single transistor FM transmitter I mentioned. It easily transmits 30 metres without antenna (probably leakage from inductor). www.nickhill.co.uk/single_trans_FM_Xmit.html

+Brandon Martinez I use Digikey most of the time

+Brandon Martinez You can also find most of what you need on Ebay if you are willing to wait a while. The stuff from China is dirt cheap but takes about two weeks to get to the US.

He’s lying it’s almost impossible to track so the FCC and your teachers will just tell you it’s easy to track

Should be the same yeah

Hehe

Just had to scroll for two seconds to find people mentioning the cat...

They can cut them to pretty much any size you want if your circuit design fits in it. And then after they're made they (or you if they don't) can drill holes if you desire for mounting.

ScienceMarc you can get inductors from ebay.

+Fabianwew oh i found it myself. Where do you recommend buying the max2606?

+Fabianwew ok bought the chip. can i use any 390nh or this specific inductor? sorry for all the questions.

+Fabianwew Use the specific parts I describe in the BOM

+Fabianwew and where is the "jack" supposed to go. The microphone werent listed so what microphone should i buy?

Fabianwew Someone vandalized the Octopart BOM. Use the information in the .csv file

+leerman22 try it out

The BOM is in the description section...

@@Afrotechmods I just looked again and I don't see anything in the description of source for the inductor but thanks for replying.

if you put it through a resistor between it then it should be possible (he talked about swinging mV's so the resistor will pull it down to mV's)

Yes that is why I broke out TUNEPAD. Make sure your audio is AC coupled and divided down to be about 1mV

can you please do a video on this?