Hello.
I've made a FM transmitter from this schematic:
The problem is that ....
Let's say I am tuning the capacitor and I begin broadcasting at 100Mhz (I can hear my music). As soon as I remove my ALL PLASTIC screwdriver from the rotor of the tuning capacitor, the frequency of the tank circuit changes. It seems as if when I am tuning the capacitor, I become the antenna or the reactance of my body is affecting the tank.
I've tried so many things. I'm not even frustrated anymore, I'm angry .
During my first prototype I used a regular breadboard then I moved onto a PCB board but I still have the same problem.
So I take the FM transmitter to my car and tune the capacitor until I hear something on 89.5Mhz. When I hear my music and remove my screwdriver from the capacitor rotor, I get the same thing, a change in frequency.
Now this is what really pisses me off, and it only happens in my car, not on my clock radio. So now I have to go up or down a few frequencies to find my broadcast, but as soon as I move my body or the transmitter, the frequency changes AGAIN!
What can I do? I am aware that I can just buy a premade FM transmitter but my goal is to learn something.
I appreciate all help.
Also, something I've considered is removing the tuning capacitor and just use a regular fixed value capacitor. Will this solve all my problems? I haven't tried it yet since I would have to de-solder the tuning capacitor. I've wasted at least 16 hours doing this (past three days) and don't want to waste any more time without getting some advice.
I bought this tuning capacitor from a HAM radio website...why would they make the rotor conductive?
I've made a FM transmitter from this schematic:
The problem is that ....
Let's say I am tuning the capacitor and I begin broadcasting at 100Mhz (I can hear my music). As soon as I remove my ALL PLASTIC screwdriver from the rotor of the tuning capacitor, the frequency of the tank circuit changes. It seems as if when I am tuning the capacitor, I become the antenna or the reactance of my body is affecting the tank.
I've tried so many things. I'm not even frustrated anymore, I'm angry .
During my first prototype I used a regular breadboard then I moved onto a PCB board but I still have the same problem.
So I take the FM transmitter to my car and tune the capacitor until I hear something on 89.5Mhz. When I hear my music and remove my screwdriver from the capacitor rotor, I get the same thing, a change in frequency.
Now this is what really pisses me off, and it only happens in my car, not on my clock radio. So now I have to go up or down a few frequencies to find my broadcast, but as soon as I move my body or the transmitter, the frequency changes AGAIN!
What can I do? I am aware that I can just buy a premade FM transmitter but my goal is to learn something.
I appreciate all help.
Also, something I've considered is removing the tuning capacitor and just use a regular fixed value capacitor. Will this solve all my problems? I haven't tried it yet since I would have to de-solder the tuning capacitor. I've wasted at least 16 hours doing this (past three days) and don't want to waste any more time without getting some advice.
I bought this tuning capacitor from a HAM radio website...why would they make the rotor conductive?
Last edited: