Relaxing kit build: FM transmitter

Another relaxing and easy kit build - this time it's an FM transmitter.
This one went together quite easily and actually worked first try.
If you want one of your very own, here are a few links:
eEbay: pileofstuff.ca...
Banggood: pileofstuff.ca...
Aliexpress: s.click.aliexp...
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This isn't the only way to do it.
It's probably not the best way to do it.
But it's how I did it.

[@craftymulligar]

Build something similar but was completely homemade and different design. It had trimmer cap instead and you would expand the coil to change frequency.

[@matambale]

@6:43 "I apologize for the [?] I won't let it happen again" . Nulling? Knowing? Kent, what? It's driving me nuts. Ok, a short trip.

[@pileofstuff]

en.everybodywiki.com/Knolling

[@tinygriffy]

@@pileofstuff didn't know there was a word for it :) Indeed "we" are not comfortable with you knolling around so much :D

[@onecircuit-as]

Oh, I was wondering about that as well! I heard it as “knowing” and thought “it’s ok to know stuff!” 🤦🏼‍♂️

[@matambale]

@@pileofstuff Thank you. And keep knolling.

[@Mr.Unacceptable]

I built a few of these a couple of years back. Now I use them to play a couple of stations everyone enjoys. I live in a valley with CBC and Monotonous FM for radio. I wish you could modify these for 15-50W signals. No competition so no need for a licence. The entire dial is empty. I put on a talk radio a classical station a rock station and Alt rock station and let people listen. I broadcast upto a mile around me. So nice having choices now. I plug them into old 7inch laptops playing streaming stations. I found plastic cases I covered in copper tape that work well for shielding.

[@TheEmbeddedHobbyist]

Should be fun while we still have an FM band. we are slowly being pushed digital, first TV and next radio. If they can sell the FM band off to somebody the buggers will, in the UK anyway

[@MC-emmcee]

The "planned" switch off is 2032 (has already been put back from 2030) . So ten more years (at least) of UK FM. If it is found that a lot of listeners still use FM it may even be put back further. It will also really depend on the technical quality and, more importantly, the accessability of the digital service.

[@pileofstuff]

We still don't have anything like DAB here in North America. I doubt FM (or AM) broadcast are going anywhere here for a while yet.

[@eldontyrellcorp]

I have already built 2 FM transmitters (stereo ones). My next project will be to connect an esp32 radio to it, to broadcast whatever online radio I want. Because, clearly, very soon, there won't be any FM radios left given my country (and probably all of Europe countries) has decided to push dab+ and to drop FM in the short term. So I'll be able to continue to use all my radios (and I have a ton of them at home, from tube radios to 70's hifi and 80's boomboxes)

[@AnotherMaker]

That's a really fun project. I really could see a bunch of little semi-practical uses for that. Pretty fun. The first thing that comes to mind would be to give one of those old computers that loads stuff off a cassette "wifi" where the cassette broadcasts and then you output the radio headphone jack into the cassette port (with some filtering). Or some pirate radio.

[@GnuReligion]

Nice! Amazed you know how that circuit works. Its all magic to me. Its a little sad the kit does not provide film caps for the audio signal path. I cheated at put a wire on a Raspberry Pi pin to play with transmitting FM once. All software. Think I sent you an msop10 FM receiver chip over a year ago, with the needed ferrites, in a little baggie. You are well on your way to a walkie-talkie. We all live under the constant drone of that 60-cycle hum.

[@Error42_]

What I want to know is if that little hand on the end of a stick turns into an hour glass when you have to stop and think about something?

[@pileofstuff]

Things aren't nearly that advanced around here.

[@Error42_]

@@pileofstuff That's not necessarily a bad thing 🙂 I do like the pointy stick anyhow.

[@Johadart]

Kent, awesome build video, keep up the great work mate 🤙🏼🇦🇺

[@albanana683]

Thank you for your "kid in a sweet shop" joy at having it squawk first time - made my day.

[@Franktek12]

Perfect thing for monitoring my laundry room. Thanks!

[@captcraig777]

Very nice! I have been asking about this. Glad to see that you have taken the time to build it. Thanks for the content!

[@SpeccyMan]

The power LED IS on the schematic! 😉

[@RicardoPenders]

pretty cool, this can be used as a listening bug. What distance does the signal go?

[@HazeAnderson]

"No static at all ... " 😏👉

[@pileofstuff]

fffff mmmm!

[@frankowalker4662]

I got one of these a couple of years ago. It worked fine, but short range and mono. So I got a stereo kit version with higher power output, coupled it with an SD Card reader/player and a small stereo amp with tiny speakers and put the whole lot in an enclosure. It transmits upto 100 meters. LOL

[@tinygriffy]

I find it pretty mind blowing that this half hand full of discrete components actually is a FM radio transmitter. I wonder what the range could be .. with a nice antenna and maximum voltage .. better than wifi ? then it would probably useful to transmit sensor data from a far away esp or something .. neighbours wondering about the new channel on 87,3 with the strange 80's modem noises all the time :)

[@pileofstuff]

The range is probably at best

[@michaeltempsch5282]

Might want to check out the guy with the Swiss accent (Andreas Spiess) for transmitting stuff over distances with microcontrollers...

[@tinygriffy]

@@michaeltempsch5282 I don't really have a far away ESP I need to get sensor data from, but thanks ! I know Andreas Channel, I think it is one of my oldest subscriptions ;). I guess it would be LoRa then anyways :D

[@Elnufo]

That was a good result, well done.

[@fredflintstone1]

Nice video would be great if it had a small receiver kit matched to it you could have a little radio mike then HA HA! would be crap quality though🙂

[@pileofstuff]

Funny you should mention that... I do have such a kit. I'm sure it'll surface one of these days.

[@strayling1]

The Banggood listing linked above has a transmitter/receiver pair in one of its related links.

[@BrianBoniMakes]

The last wireless mic you had was illegal, is this one okay to use?

[@pileofstuff]

As long as it's power is low enough. And this one seems to be weak enough to be acceptable.

[@tenminutetokyo2643]

DOOD!

[@onecircuit-as]

What a great build and the explanation of the circuit was very edifying - I reckon radio is your superpower! One question - what is the nature and length of the antenna and does it matter? 🤔

[@pileofstuff]

It's been decades since I exercised my antenna theory, but... The length of the antenna should *optimally* be an even fraction of a wavelength (full, half, quarter, eighth...) for maximum efficiency. In this case with 80Mhz, 1 wavelength would be 3.747406 Meters, The provided antenna wire is only about 15CM, so won't be a particularly good match. But in this case, "close enough" is close enough. At a higher power, the impedance mismatch could cause reflected power and possible harm the amplifier.

[@onecircuit-as]

Interesting! Do you have any recommendations for books or sites to explore this a little further? My finance minister is also very unhappy that I had to order the kit to make sure it was all legit. 😬

[@pileofstuff]

@@onecircuit-as Not sure if my old college textbooks are still in print... This site seems to have a lot of the theory laid out pretty well (if you ignore the colour scheme) Warning: its a very math heavy topic www.antenna-theory.com/tutorial/smith/smithchart5.php www.antenna-theory.com/antennas/shortdipole.php

[@onecircuit-as]

Who doesn't like lots of math! 😜 Thank you so much. 👍

[@markusallport1276]

I love building these little kits. I just finished the FM radio kit with silly lights but great reception. USB powered, fun stuff.