how to convert digital trasmission to analog?

Other Hardware General Electronics
1

i buy this chip http://robotics.reefat.com/wp-content/uploads/2009/01/tlp434-rf-transmitter.jpg

i want trasmit the signal in analog mode not in digital mode..

this is the code..

#include <VirtualWire.h>

void setup()
{
    Serial.begin(9600);   // Debugging only
    Serial.println("setup");

    // Initialise the IO and ISR
    //vw_set_ptt_inverted(true); // Required for DR3100
    vw_setup(2000);  // Bits per sec
}

void loop()
{
    const char *msg = "hello my friend";

    digitalWrite(13, HIGH); // Flash a light to show transmitting
    vw_send((uint8_t *)msg, strlen(msg));
    vw_wait_tx(); // Wait until the whole message is gone
    digitalWrite(13, LOW);
    delay(500);
}

this work but i receive the output in wfm iwant the signal in am..
can anyone help me to this?

2

Virtualwire library works to send bytes of data from transmitter to receiver.
If you want to send AM signal, then you need an AM transmitter.

Unless you intend something different by the use of "am".

3

Datasheet? These very simple transmitters are designed only for OOK (on-off-keying),
and won't necessarily work as you are wanting (certainly I wouldn't expect any level
of linearity)

4

in datasheet is a "am" trasmitter..is the same of thishttp://www.quasaruk.co.uk/acatalog/AM_Modules.html

5

AM in this sense:
The 1's go out at one signal level, the 0s go out a different signal level. The frequency does not change.

Vs FM, where the frequency would change for 0 vs 1.

6

Whats that means is that the Transmitter sends data by the amplitude modulation of the transmitters carrier wave,
ie turning it on and off.
They cant be linearly modulated, which is what is needed for true AM transmission.
But what is your goal here, why do you need AM transmission?

7

The transmitter the OP referred to, actually uses ASK (Amplitude Shift Keying).

8

Yes that's correct, but those simple 433.92 transmitters only support 2 binary states, on and off.
they don't support multiple amplitude states, or the ability to transmit multi byte symbols.

9

OK fair enough in which case those transmitters offer no real advantage over the OOK ones at low data rates.
Like you, I'm also wondering as to why the OP wants "AM", perhaps he wants to make a simple receiver/demod system himself in which case the OOK ones would probably make it easier for him as he just has to check for carrier versus no carrier.

Demod433.jpg