FM/AM Detectors

[Jason]

Can anyone explain to me, or post a link on, what an AM/FM detector is and
specifically what is its purpose? My searches have revealed some schematics
of detectors but little towards their actual purpose.

I have a project at school I have chosen to do which is building a simple AM
radio. The problem is our communications book is extremely unhelpful. I
believe its only mention of detectors is in a "circuit diagram" which is
actually nothing more than a square with the words "FM detector" or
something similar written inside of it.

Other students have bought radio kits for their projects and the instructor
accepts those. I on other hand want to design my own and learn the
principles and theory behind reciever design.

Thanks in advance.

 

[Peter Bennett]

Can anyone explain to me, or post a link on, what an AM/FM detector is and
specifically what is its purpose? My searches have revealed some schematics
of detectors but little towards their actual purpose.

I have a project at school I have chosen to do which is building a simple AM
radio. The problem is our communications book is extremely unhelpful. I
believe its only mention of detectors is in a "circuit diagram" which is
actually nothing more than a square with the words "FM detector" or
something similar written inside of it.

Other students have bought radio kits for their projects and the instructor
accepts those. I on other hand want to design my own and learn the
principles and theory behind reciever design.

Thanks in advance.

Go to a library, and look for books on Amateur Radio - in the US, you
should find the ARRL Radio Amateur's Handbook - that book should cover
the material you need.

 

[Jason]

Alright, thanks.

I just recieved an older communications book from my brother and it states
that detection and demodulation are the same thing. That clears things up,
as I knew what demodulation was.

 

[Steve]

Can anyone explain to me, or post a link on, what an AM/FM detector is and
specifically what is its purpose? My searches have revealed some schematics
of detectors but little towards their actual purpose.

it extracts the original signal from a modulated carrier. Try getting
a better book, sounds like that one isn't worth the paper it's printed
on.

your favorite radio station modulates music onto a carrier wave for
transmission. Your radio receives this carrier and demodulates it to
extract the music. A very simple radio receiver can be made from a
diode detector and a few bits and peices.

Plenty on the web about this, there's also amateur radio newsgroups
that will help you a lot.

a detector is also known as a demodulator.

nifty

 

[Kevin Aylward]

Can anyone explain to me, or post a link on, what an AM/FM detector
is and specifically what is its purpose? My searches have revealed
some schematics of detectors but little towards their actual purpose.

In a very simplified nutshell.

1 If you send a signal to a length of wire, it radiates a bigger signal
the higher in frequency it is. Audio frequencies don't radiate much at
all.

2 AM and FM are methods used in order to increase the frequency of the
signal to achieve bigger radiation as described in 1.

3 The higher transmission frequency is generated (coded) from the signal
frequency by a "modulator".

4 The received signal frequency is generated (decoded) back from the
transmitted higher frequency by a "detector". A detector is also called
a "demodulator".

Thus, 3 and 4 define what a "modulator" and a "detector" are. That is,
they are devices that convert information at one frequency to
information at another frequency.

Kevin Aylward
[email protected]
http://www.anasoft.co.uk
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.