fm radio help

[catcat]

After all those superhets, superregens and stuff I decided to take a new turn. I decided to go with a simple crystal or ceramic tuner to select the specific range of freqencies, and the simplest possible detector. I also want some guidance about the rf and audio amplifiers as well as the rest. And i dont care about no static or state-of-the-art quality.

 

[ZIGGY_DAN]

Crystal, for pure simplicity.

 

[Hero999]

I've voted for superhet though I prefer PLL to be honest.

 

[JimB]

What is a "ceramic tuner"? Never heard of it.

If you are trying to receive FM, a crystal set WILL NOT WORK.

Also be aware that when used to receive AM, a crystal set has very poor selectivity and sensitivity. You will need a long antenna to receive anything at all, and then if you are lucky you will receive several stations at the same time. The single coil just does not have enough "Q" to give reasonable selectivity.

JimB

 

[Hayato]

Your crystal set won't work.
The tank-oscillator circuit was splited by the transistor and the diode (crystal) there.

First you need to parallel the oscillator coil with the capacitor (LC), forming a oscillation circuit, then you make the detector.

I like regen sets, they are cool.
But superhet works better.

 

[catcat]

There are crystal fm radiosThat select a renge of frequencys

 

[catcat]

What is a "ceramic tuner"? Never heard of it.

If you are trying to receive FM, a crystal set WILL NOT WORK.

Also be aware that when used to receive AM, a crystal set has very poor selectivity and sensitivity. You will need a long antenna to receive anything at all, and then if you are lucky you will receive several stations at the same time. The single coil just does not have enough "Q" to give reasonable selectivity.

JimB

I am not talking about the battery-less am crystal radio. I am talking about a system of quartz crystals thatcan select a ragge of freqencies that a re to be decoded by freqency.

 

[audioguru]

50 or 60 years ago, a crystal "radio" picked up the only AM radio station in town.
Now it will pick up all the radio stations at the same time.

A crystal radio has only a single tuned circuit. A real radio has many tuned circuits to separate the stations.

 

[catcat]

Then whats a crystal weatheradio? It has to tune and its fm.?

 

[JimB]

I am talking about a system of quartz crystals thatcan select a ragge of freqencies that a re to be decoded by freqency.

So, you are going to use one crystal for each station you want to receive, or, are you going to build a multi-crystal synthesiser to tune 88 to 108 Mhz in 50khz steps?

Have you any idea how much crystals cost? No not the mass produced standard frequencies, but ones made order on your specified frequency.

JimB

 

[audioguru]

Then whats a crystal weatheradio? It has to tune and its fm.?

You can make a super-het radio that uses a crystal so that it accurately tunes a single frequency for weather radio. Since the highest crystal frequency is much too low for the VHF weather radio frequencies then you will also need to make a frequency synthesizer circuit for it.

To get the parts you will need to buy a crystal controlled super-het weather radio.

 

[oldtimer]

I think you should read a few books on the subject and you will soon realise what most of the people are saying. F.M. needs a stable Frequency source since the intelligence in the signal is in the amount of shift from the centre frequency. So a receiver needs a very stable oscillator like a Phase Locked Loop (PLL) good front end design and a well laid out discriminator.

 

[Nigel Goodwin]

Then whats a crystal weatheradio? It has to tune and its fm.?

Never heard of such a thing?, a 'crystal set' is (these days) a simple tuned circuit followed by a germanium diode detector, it's AM only, requires a huge outdoor aerial, and only receives close strong signals. Originally it used a tuned circuit and a piece of 'crystal', which was galena (not sure about the spelling?), and you used a 'cats whisker' (fine springy wire) to locate a sensitive spot on the crystal.

Presumably your radio is a superhet with a PLL synthesiser?, which uses a quartz crystal as the reference frequency - however, in no way could it be called a 'crystal' radio. As for 'ceramic radio', again theres no such thing!.

 

[ZIGGY_DAN]

Perhaps in his title he ment to put AM (amplitude modulation) instead of FM (frequency modulation). could be a simple mistake, when I said crystal I was talking about AM.

With my crystal radio i can pickup 5 or 6 separate stations and tune in to hear just one, at night i can hear french and german stations.

 

[Hayato]

Never heard of such a thing?, a 'crystal set' is (these days) a simple tuned circuit followed by a germanium diode detector, it's AM only, requires a huge outdoor aerial, and only receives close strong signals. Originally it used a tuned circuit and a piece of 'crystal', which was galena (not sure about the spelling?), and you used a 'cats whisker' (fine springy wire) to locate a sensitive spot on the crystal.

Presumably your radio is a superhet with a PLL synthesiser?, which uses a quartz crystal as the reference frequency - however, in no way could it be called a 'crystal' radio. As for 'ceramic radio', again theres no such thing!.

Maybe he meant a radio that uses a ceramic resonator in the oscillator stage.

But his drawing shows some sort of galena radio.

 

[catcat]

Can you use an oscilator to detect fm?

I thought that you could make a tuner that selects a range of freqencys by crystal resonators.

 

[audioguru]

A frequency discriminator circuit detects FM, not an oscillator. An oscillator just oscillates.

They don't make crystals for very high frequencies like for FM stations.
You use a crystal of a lower frequency and a frequency-multiplier circuit.

Modern radios use a frequency synthesizer circuit with just one crystal. To tune it you use a pushbutton that changes the multiplication ratio of the circuit.

 

[catcat]

A frequency discriminator circuit detects FM, not an oscillator. An oscillator just oscillates.

They don't make crystals for very high frequencies like for FM stations.
You use a crystal of a lower frequency and a frequency-multiplier circuit.

Modern radios use a frequency synthesizer circuit with just one crystal. To tune it you use a pushbutton that changes the multiplication ratio of the circuit.

Whats a frequency discriminator and freqency synthesizer?

 

[Nigel Goodwin]

Whats a frequency discriminator and freqency synthesizer?

Basic building blocks for any remotely modern FM radio!, I suggest you try getting some books - the ARRL and RSGB Handbooks are highly recommended if you're playing with radio gear (and good for general electronics).

 

[HiTech]

There are crystal fm radiosThat select a renge of frequencys

C'mon dude, let's get on the same page here with that grammar ... or are you addressing some electronics newbie in Botswana?