How old receivers work with digital AM radio transmission?

is nowadays AM radio transmission is analog or digital (may be my doubt is silly but please clear my doubt). if it is digital then how can the old receivers can receive them.
thanx

am transmission

As far as I am concerned comercial AM transmission are analog.

AM, AM-SSB, FM, PWare analog modulation techniques while FSK, PSK , QAM are digital.

Obiviously the last are primaly digital techniques usually found in books, there are a miriad of other digital modulations that can be more efficient than these , including the ones with codes modulation .

am transmission

is anakig, but if you want learn more about this, you should read "Communications Systems" by Haykin

Added after 1 minutes:

sorry man, in my last message i try tell you "Analog".

Re: am transmission

amplitude modulation is analog communication
or else...how can we say that we modulate the amplitude in it...it has to be an analog signal, since digital signals have discrete defined levels at discrete times

Re: am transmission

Amplitude modulation (AM) is a form of modulation in which the amplitude of a carrier wave is varied in direct proportion to that of a modulating signal. (Contrast this with frequency modulation, in which the frequency of the carrier is varied; and phase modulation, in which the phase is varied.)

AM is commonly used at radio frequencies and was the first method used to broadcast commercial radio. The term "AM" is sometimes used generically to refer to the AM broadcast (mediumwave) band (see AM radio).



Forms of AM

In its basic form, amplitude modulation produces a signal with power concentrated at the carrier frequency and in two adjacent sidebands. Each sideband is equal in bandwidth to that of the modulating signal and is a mirror image of the other. Thus, most of the power output by an AM transmitter is effectively wasted: half the power is concentrated at the carrier frequency, which carries no useful information (beyond the fact that a signal is present); the remaining power is split between two identical sidebands, only one of which is needed.

To increase transmitter efficiency, the carrier can be removed (suppressed) from the AM signal. This produces a reduced-carrier transmission or double-sideband suppressed carrier (DSBSC) signal. If the carrier is only partially suppressed, a double-sideband reduced carrier (DSBRC) signal results. DSBSC and DSBRC signals need their carrier to be regenerated (by a beat frequency oscillator, for instance) to be demodulated using conventional techniques.

Even greater efficiency is achieved—at the expense of increased transmitter and receiver complexity—by completely suppressing both the carrier and one of the sidebands. This is single-sideband modulation, widely used in amateur radio due to its efficient use of both power and bandwidth.

A simple form of AM often used for digital communications is on-off keying, a type of amplitude-shift keying by which binary data is represented as the presence or absence of a carrier wave. This is commonly used at radio frequencies to transmit Morse code, referred to as continuous wave (CW) operation.

In 1982, the International Telecommunications Union (ITU) designated the various types of amplitude modulation as follows:
Designation Description
A3E double sideband full carrier - the basic AM modulation scheme
R3E single sideband reduced carrier
H3E single sideband full carrier
J3E single sideband suppressed carrier
B8E independent sideband emission
C3F vestigial sideband
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