Make a simple AM transmitter

Make a simple AM transmitter that will cost you less than $5.

Step 1 Stuff you need

A crystal whos frequency is between .9000 and 1.2000 MHz.
Some wire
A male headphone jack
A breadboard or experimental circuit board (optional)

Comments

[electronicz]

I have a 1.00 MHz crystal like bmlbytes, how high of a voltage can this crystal withstand?

[account3r2]

if i make my own transmitters and receivers using a 50 MHz crystal, since the crystal isnt in the FM or AM range, would the FCC rules apply to it?

[gspeed0689]

That is in the Amateur Radio range, and this circuit does not have enough power to really go far. Low power projects like this aren't enforced by the FCC, it's much like one of those mp3 audio devices that broadcast your mp3 player on a radio station in your car.

If you were to boost the power, you would then be subject to FCC rules.

[nodoubtman]

do you need an audio transformer for this? i have a 600: 600 ohm 1 to 1

Thanks!

[nodoubtman]

what kind of antenna do you use ?

thanks!

[David97]

Just some wire shold do it.

[drbill]

I've never seen a transmitter this simple !

[nodoubtman]

I have a crystal of 1.8432 Mhz , is it okay?

thanks!

[nqzdepofltr]

Any crystal will work. All you have to do is get the crystal of the frequency you want ;)

[nodoubtman]

what does this circuit does in reality??

thank you! :)
marC:)

[Bot1398]

Your username says nodoubtman but look you have a doubt!!! :P

[almamater]

ahhhh very good!!

[account3r2]

between .9 and 1.2? :P all i have are 9 crystals that are 50MHz and a mysterious 2 legged one labeled 33.8688

[atonix]

I think that we can increase its power by using an audio transformer .

[jgabrielian]

how can i increase power?

[Wesley666]

Also what if I want FM not AM?

[trashman1990]

like i said below, fm is modulated different compared to am, the transmission frequency of fm is based of off amplitude or as the amplitude of the audible sound wave increases the frequency of the transmission increases, but with am, as the amplitude of the audible sound wave increases so does the amplitude of the transmitter though the transmission and audible sound dont have matching waveforms... i think i explained that right (hope so)

[fgul]

Can we use an NE555 based oscillator instead of a crystal oscillator for this`AM transmitter circuit?

[trashman1990]

You would not be able to replace the crystal with a 555 timer for this specific circuit, but... you can make a much better transmitter if you base the oscillator off of a 555 circuit, although it would be a lot more complicated than this. I would try to get a basic understanding of amplifier circuits (not just opamps) and learn what signals look like before and after it had been modulated for am transmission, before I would dive into a 555 based transmitter. It would be a lot of fun and a good learning experience tho. ....Maybe I should maybe make a how to sometime....

[Wesley666]

OK thanks

[ReCreate]

get a 100MHz oscillator ...and tune your radio to 100MHz FM

[Wesley666]

so I would tune a radio to 33.3 FM if I had a 33.33 MHz oscillator. (The only oscillator I have is 33.33 MHz) Also how would you build a receiver for a specific Frequency? (Preferably 33.33 MHz!)

[ReCreate]

well first fm is from 87MHz to 108MHz what you have there is close to the range of remote controlled airplanes,49 i suppose you might be able to modify a radio to recive 33MHz (try by turning the little "screws" on the radio's circuit board?) also,since it is not in the am or FM range,you could broadcast it for MILES,ive hear of someone sending morse code from one side of the country to the other at 20something MHz

[M0HIZ]

Firstly, FM and AM and not bands of frequencies, they are types of modulation. Secondly, do not try to modified a radio to receive on a different frequency as you will almost certainly change the tuned circuits to something totally different to what you want. Finally, it is very common for people to talk to poele or send Morse code to people on different continents or the other side of the world. This is one of the many aspects of ham radio.

[Wesley666]

very cool. I found it in a computer motherboard or whatever and I tested it and it worked and I have never touched it since. I was hoping to build a receiver specifically for 33.33 MHz and I was wondering how I would go about that, and if it helps I have a crystal (two pins) with the same 33.33 MHz range if that helps. Thanks

[ReCreate]

if you find a crystal(2-legged) in a computer,it is used for timing,thats why replacing the crystal in a gameboy color speeds up the game. it speeds up the timing,making time trials unfair,crystals are used to keep track of time in computers,but oscillators...i have no clue why that would be inside a computer

[trashman1990]

crystals are a very important part of an oscillator, normally they are used in a oscillator circuit to set the frequency, and yea, the crystals on mobo are for timings, the 33.33 mhz crystal on the motherboard is to control the timings on pci slots, may pci cards also have 33mhz crystals on them,

[Wesley666]

this isn't a crystal its a oscillator, so it gives off a signal at that frequency, crystals don't give off signals, plus I have never seen a computer with another one in it ever and the computer it came out of had no 33.33 MHz crystals in it any how, they were all 14.6 MHz.

[trashman1990]

i assumed it was a crystal because he said 2 pin, never heard of a 2 pin ocillator. most new motherboards have digital oscillators so you can set the pci bus clock in the bios, so you might not see many crystals (if any) on new boards, im not sure what 14.6 mhz would time

[Wesley666]

well the computer it came out of was older then the dinosaurs but the frequency is 33.33 MHz and all the other crystals were 14.6 MHz so I have no idea what it was doing.

[account3r2]

i still have my windows 3.1 computer up in my garage somewhere... it used to run DOS so im sure my computer has plenty of crystals

[Wesley666]

I have seen many crystals (two legged) in a computer but I have only ever had this one with an oscillator in it. Very unusual.........

[computergeek]

Really neat idea! But do you have to worry about the FCC Because you are transmitting radio signal?

[bmlbytes]

Not if its not too powerful

[fgul]

Can't we use NE555 IC based oscillator?

[computergeek]

Thanks! Also I found a copy of the FCC Rules and regulations available here. See section 15.23 home built devices.

[static]

If your intent is to act as a low power broadcaster, I believe FCC regulations other than Part 15 may apply. In the event there isn't the following would be the applicable portion of part 15;

---

Section 15.219 Operation in the band 510 - 1705 kHz.

(a) The total input power to the final radio frequency stage (exclusive of filament or heater
power) shall not exceed 100 milliwatts.

(b) The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3
meters.

(c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at least 20 dB below the
level of the unmodulated carrier. Determination of compliance with the 20 dB attenuation specification
may be based on measurements at the intentional radiator's antenna output terminal unless the intentional
radiator uses a permanently attached antenna, in which case compliance shall be demonstrated by
measuring the radiated emissions.

---

The above "jives" with what I have read on the topic since 1968. Fairly restrictive, doesn't allow for a very effective antenna in the AM broadcast band

[______]

Do youy have a pic of yours fully assembled, can you post it?

[the.texas.trucker]

I'm assuming a 46000.00 KHz crystal would be way too high a frequency to use with a standard radio, correct? That would be something like AM 4600 right?

[bmlbytes]

First of all, that is 46MHz and yes, that is out of a standard radio range.