Re: How transmitters work.
- From: Jamie <jamie_5_not_valid_after_5_Please@xxxxxxxxxxx>
- Date: Wed, 20 Apr 2005 18:56:26 -0700
Jason wrote:
lets break it down in a different form.Please forgive the pure ignorance of this question. I understand that this is very basic stuff that I should probably know, but I have never been to class to learn about this stuff, nor have I found any tutorials that explain this stuff in simple everyday terms. I passed by technician and general class amateur license exam by memorizing the right buzzwords for this stuff, but not actually understanding the concepts. I admit, I am ashamed of this fact. Here's what I have gathered so far.
1. DC current flows through a crystal. 2. The resonance of the crystal causes the current to form waves around the frequency of crystal 3. This new "pulsating" current is then amplified and then sent through the crystal again. (This is called positive feedback) 4. The pulsating current is sent through a low-pass filter to "filter out" unwanted frequencies. (That's why I said "around the frequency" of the crystal) 5. From the filter, the current flows to an antenna which converts the current to RF radiation.
Comments and help would be greatly appreciated.
forget the crystal idea for now, that is only a source to generate
a stable frequency reference!. there are other ways.
any ways.
lets first start with the signal generator..
This generator will produce AC (alternating current/Voltage) at a rate
per second that is equal to the frequency of what you want to transmit on.
for example:
1.6 Mhz, = 1600000 times per second will an alteration of a signal going from 0 Volts, to Full Volts+, back to 0 volts, then Full Volts-, and then back to 0 volts completes a full cycle.
this signal is most likely then past to an amplifier to increase the output power abilities.
it then makes it to the antenna as a sine wave (AC), at that point the AC will generate an electro magnetic field via the antenna..
this field is powered by the AC energy you are creating.
and since its now magnetic, the principles of Unlike and like
polarities apply..
minus and minus for example repel the magnetic energy that
was there before gets pushed away.. this is how the energy actually travels in space.
Known as a simple carrier, it really does nothing for you other than allows another
receiver some where detect your transmitter as being there.
CW (Morse code)is a good example
systems like AM (amplitude modulation) will modify the level of this
sine wave power output to reflect the patterns of the audio frequencies.
because your transmitter frequency is so much higher than your audio freq, many cycles of your carrier freq will be sent out in space changing power levels in very gradual steps! but the receiver at the
other end is converting this carrier into a DC (direct Current signal) where is the level of voltage that is changing depending on the Level of the signal which is influenced by the audio//
etc.//
if you need a deeper detailed than that i think i can also supply that also. this looked as simple as i could explain it.
.
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