How to lower watt output

Thread Starter

Honnzoun

Joined Aug 13, 2021
7
Hi, I am kinda new to this stuff but I have 16mA 3.3V AC output wich is 0.0528 watts but I need to get it to 50nW (0.05 microwatts) I tried finding something butndont really know so how do I do it?
 

Thread Starter

Honnzoun

Joined Aug 13, 2021
7
In czechia we are allowed to transmit FM radio on maximum at 50nW so odk how to get it from 16mA 3.3V to output 50nw
 

Juhahoo

Joined Jun 3, 2019
215
The transmit regulation means your RF power, not the supply power...You need to dig deep to the PA circuit to be able to alter its output power. Easiest is to add simple antenna attenuator or build one, but this is quite challenging.
 

Thread Starter

Honnzoun

Joined Aug 13, 2021
7
I am sure about the 50nW and I want to use raspberry pi with gpio pin wich outputs at 3.3v 16amp and than connect anthena (simple 20-40cm wire) with some resistors
 

Juhahoo

Joined Jun 3, 2019
215
Actual start for the thread makes no sense at all, now we are already building an FM transmitter out of R-Pi when we just wanted to lower the power from the output...:rolleyes:
 

Audioguru again

Joined Oct 21, 2019
3,632
Years ago, Silicon Chip magazine in Australia had a project and a kit called Micromitter which was an FM stereo transmitter.
It had an attenuator on its RF output to reduce its transmitting power output (I do not know how much) for a range of only 20m.
 

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Thread Starter

Honnzoun

Joined Aug 13, 2021
7
Can someone just tell me how many Ohms I need to get 50nW i calculated 2178 mega ohms but that seems huge so I wanna know if its right.
 

BobTPH

Joined Jun 5, 2013
3,769
Your calculation of the power is flawed. The IO port might be able to supply 18 mA but, connected to a wire as an antenna, it will not produce anywhere near that current.

Also, my research inducates that the fastest you can toggle a GPIO pin is 25MHz. You might be able to get into the FM band with harmonics, but.this would be transmitting at higher power at the fundamental frequency, which is likely not legal.

There are many good one FM transmitter circuits out there using only a few components. Build one of those instead.

Bob
 
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