Please take a look and give feedback on my Personal Project mini FM radio transmitter

Thread Starter

lukekers

Joined Oct 17, 2015
13
MOVE the cap. As stated earlier. EVERYTHING is affected at 100 MHz.

Another question. Will the antenna be inside a plastic container of some sort or just be a live wire extended into space?
Because I will be making a tutorial for others I need to consider availability of components therefore It will simple be a live extended antenna, something you would find on kids remote control cars and remotes.
 

MrAl

Joined Jun 17, 2014
6,604
Hi,

Better off starting from something crystal based or the frquency will keep drifting. Most capacitors and transistor params drift to much over temperature and hand movement and silly stuff like that. Crystals dont vary that much and work very well for radio.

I did not do that much work in radio over the years as i was always involved in something else. but i did do a little work and the best i got with FM was with a crystal based oscillator and regular FM receiver. I got maybe 1/2 mile to 1 mile range with very little power, but my antenna was at least 20 feet up (half wave dipole i think).
You are allowed up to 100mw power transmission legally in the U.S. unless it blocks someone else's reception of something else and then you would have to switch to a different frequency.

As i said i did not do nearly as much work in radio as in other areas, but just a week ago i did do a small experiment with a friend where he transmitted over frequencies from about 2MHz to about 20Mhz and i was able to receive the carrier pretty well about 30 feet away. We used a DSP frequency generator which puts out precise frequencies due to the basic crystal oscillator it uses. The receiver had a digital turner too so i could tune to the exact frequency he was transmitting at. Antenna about 1 meter long.
That's about the simplest way to do it for the lower frequencies. If you dont need variation in frequency for different purposes then a single frequency crystal oscillator would work ok, but using a small commercial made receiver works better than anything you could probably build yourself.
 
Last edited:

Thread Starter

lukekers

Joined Oct 17, 2015
13
Hi,

Better off starting from something crystal based or the frquency will keep drifting. Most capacitors and transistor params drift to much over temperature and hand movement and silly stuff like that. Crystals dont vary that much and work very well for radio.

I did not do that much work in radio over the years as i was always involved in something else. but i did do a little work and the best i got with FM was with a crystal based oscillator and regular FM receiver. I got maybe 1/2 mile to 1 mile range with very little power, but my antenna was at least 20 feet up (half wave dipole i think).
You are allowed up to 100mw power transmission legally in the U.S. unless it blocks someone else's reception of something else and then you would have to switch to a different frequency.

As i said i did not do nearly as much work in radio as in other areas, but just a week ago i did do a small experiment with a friend where he transmitted over frequencies from about 2MHz to about 20Mhz and i was able to receive the carrier pretty well about 30 feet away. We used a DSP frequency generator which puts out precise frequencies due to the basic crystal oscillator it uses. The receiver had a digital turner too so i could tune to the exact frequency he was transmitting at. Antenna about 1 meter long.
That's about the simplest way to do it for the lower frequencies. If you dont need variation in frequency for different purposes then a single frequency crystal oscillator would work ok, but using a small commercial made receiver works better than anything you could probably build yourself.
Thanks for your feedback! Unfortunately my personal project is coming to an end and I have more or less finished building what I consider my final transmitter of which I will be making a video tutorial. I will probably try building a crystal radio for my own advantage. Fortunately, The country I live now, no one really cares about this law.
 

JoeJester

Joined Apr 26, 2005
4,126
Fortunately, The country I live now, no one really cares about this law.
I find that difficult to believe. No one cares about the law until one runs afowl of the law when the authorities come knocking on the door.

Your FM transmitter will be low power, typically less than 100 mW, which is generally authorized as long as you are not interfering with other services in the FM band.
 
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