**Project: FM-to-AM Converter Circuit – Need Complete, Functional Schematic (Like My AM-to-FM Version)**

Hello everyone, I am an old hobbyst 86 years old and excuse me for mistakes.....

I'm working on a project where I need to **convert FM signals (88–108 MHz) into AM signals (~1 MHz)** so that they can be received on a standard AM radio. I’ve already built an AM-to-FM converter using a single transistor oscillator, and now I want to create the reverse: an FM-to-AM converter.

### Goal:
- Receive a **standard FM radio station**
- Extract the **audio signal**
- **Modulate** that audio onto a **1 MHz AM carrier**
- Output it as a low-power AM signal receivable by an AM radio

---

### What I Want:

I need a **complete, working schematic** that:

- Is built using **real, discrete components** (no modules, no black boxes)
- Uses common parts like **BF494, 2N3904, NE612, LM565**, or similar
- Includes:
- FM tuning input stage (L1 + C1)
- FM demodulator (PLL or simple ratio detector)
- Audio amplifier (if needed)
- AM modulator (transistor-based)
- AM oscillator (~1 MHz, L2 + C3)
- Power supply (3V–9V)
- Antenna connections (FM in, AM out)

### ️ Components I’ve considered:

| Component | Value/Type | Purpose |
|-----------|------------|---------|
| Q1 | BF494 / 2N3904 | FM RF Amplifier |
| L1 | 5 turns (24 SWG, 5mm diameter) | FM tuning |
| L2 | 7 turns (24 SWG, 5mm diameter) | AM oscillator |
| C1 | 10pF | FM tuning |
| C2 | 0.01µF | Coupling |
| C3 | 22pF | AM frequency |
| R1 | 10K | Bias |
| R2 | 2.2K | Collector load |

---

### Usage:

- Tune C1 to choose the FM station.
- L2 + C3 set the AM output frequency (~1 MHz).
- AM output is a short antenna (10–30 cm wire) to be received by a nearby AM radio.

---

### Style:

I'd really appreciate if someone could provide a schematic **similar in layout to classic hand-drawn or educational diagrams** – something clean and simple like you'd see in textbooks.

---

Thanks in advance to anyone willing to help! This is for educational and experimental use, not for broadcasting or interference.

 

Do you really expect us to do all of the work for you on a retro project like that?

Show us all of your work on this first, your schematic, your design docs and drawings first. Then you might get help on this retro AM modulator from a person with similar interest.

In the 1970's it would have been interesting for me, today, not really as it's retro rework from the 70's

 

I would like a circuit diagram of an AM FM converter. I have an old AM tube radio and I would like to listen to FM on my old radio. Can you help me send me a similar circuit diagram to do this? I am 86 years old, an old hobbyist and I would like some help from you. That's it - Thanks and sorry

 

have an old AM tube radio and I would like to listen to FM on my old radio.

Easily done using an FM receiver and AM transmitter.

Why do you want to make it difficult?

If you must, just find schematics for the two parts and build them yourself. Hopefully you can figure out how to connect them together.

 

Easily done using an FM receiver and AM transmitter.

Why do you want to make it difficult?

If you must, just find schematics for the two parts and build them yourself. Hopefully you can figure out how to connect them together.

I wonder what's really important here. These types of requests are so detailed in using specific parts and methods but are always from just some guy, with an electronic hobby, but with little or no experience but yet, still need a complete design document down to the enclosure to put it in.

Maybe it's a cultural thing but , I have a doubt.

 

thanks for the help!!! In Italy you can't transmit in AM. , for this reason, even if it's very difficult, I would like a FM AM converter

 

This is what I would do;
-Open your AM radio and locate the volume control. It will have three terminals, ground, the wiper that goes to the audio amp and the input coming from the detector.
-Remove the last wire.
-Solder a coax cable between ground and the potentiometer’s now empty terminal.
-The other end of the coax cable connect it to any FM tuner which has an audio level output.
-You may require a Y adapter to sum the left and right channels.

 

thanks for the help!!! In Italy you can't transmit in AM. , for this reason, even if it's very difficult, I would like a FM AM converter

So now you're asking us to design a likely illegal device for you.

 

This is what I would do;
-Open your AM radio and locate the volume control. It will have three terminals, ground, the wiper that goes to the audio amp and the input coming from the detector.
-Remove the last wire.
-Solder a coax cable between ground and the potentiometer’s now empty terminal.
-The other end of the coax cable connect it to any FM tuner which has an audio level output.
-You may require a Y adapter to sum the left and right channels.

 

This is a great solution! THANK YOU ALL - Kind regards

 

This is a great solution! THANK YOU ALL - Kind regards

All you really needed was an audio amplifier for a FM tuner. Why did you think you needed this complex FM demodulator, AM modulator device?

 

All you really needed was an audio amplifier for a FM tuner. Why did you think you needed this complex FM demodulator, AM modulator device?

Please, Consider that I am 86 years old and that I can be wrong ..... sometimes .... best regards and thanks !

 

Please consider that I am 86 years old and that I can be wrong ..... sometimes .... I had an old diagram that I attach and so I thought that it could be done the other way around: from AM to FM and vice versa. Thanks to everyone , regards

 

You're not wrong or even close to being wrong. There is a principle in life and in engineering called KISS. Keep It Simple...

It only sounds easy, the reality is that you must also know the complexity of not so simple.

 

Is it important that the signal path from FM to AM be wireless?

ak

 

circuit shown is just an oscillator... say 100MHz...
when this signal is mixed with signal from AM band ... say 1MHz... result are additional frequencies... 99MHz and 101 MHz (sum and difference). but...it is not just the modulation that is different, channel bandwidth is also very different (some 30x). can you post sample audio of what you can receive using this method?

 

You're not wrong. There is a principle in life and in engineering called KISS. Keep It Simple...

It only sounds easy, the reality is that you must also know the complexity of not so simple.

OK thanks a lot

Is it important that the signal path from FM to AM be wireless?

ak

Yes I prefer

 

circuit shown is just an oscillator... say 100MHz...
when this signal is mixed with signal from AM band ... say 1MHz... result are additional frequencies... 99MHz and 101 MHz (sum and difference). but...it is not just the modulation that is different, channel bandwidth is also very different (some 30x). can you post sample audio of what you can receive using this method?

It was just a circuit I had, that I didn't quite understand. My main purpose is that I would like to listen to FM on an old AM tube radio of mine- That's it - Thanks. I turn on the AM radio and I would like to listen to FM- that's it- Thanks a lot

 

That circuit works (if it does) on several principles,

The modulating frequency (AM band) is much lower in frequency than the carrier (FM band). And the modulation of the AM signal is in amplitude. And a third that I don’t understand, the AM modulation of the FM oscillator somehow results in frequency modulation.

None of those holds when you go the other way. A similar circuit to convert FM band to AM is not going to work.

 

That circuit works (if it does) on several principles,

The modulating frequency (AM band) is much lower in frequency than the carrier (FM band). And the modulation of the AM signal is in amplitude. And a third that I don’t understand, the AM modulation of the FM oscillator somehow results in frequency modulation.

None of those holds when you go the other way. A similar circuit to convert FM band to AM is not going to work.

OK THANKS A LOT