Szczepan Bialek wrote:
"dave" napisal w wiadomosci
m...
On 04/08/2012 09:55 AM, wrote:
Many modern solid state transmitters have no "coils", per se, except
perhaps in the output low pass filter or output matching network. The
carrier is generated from a crystal oscillator (no coils, just caps and a
hunk o' rock) and amplified in broadband stages.
More like a switch mode power supply than a crystal oscillator, (the way I
visualize a modern AM transmitter without large coils.)
Are such used by radio amateurs?
S*
Since you haven't a clue what he is talking about, your question is
meaningless.
Most current, modern transmitters, amateur or otherwise, generate their
carrier frequency through digital frequency synthesizers referenced to
a crystal oscillator.
A small percentage of transmitters that are designed for either fixed
frequency use or use over a limited frequency range just use crystal
oscillators.
The output power is produced by amplifier stages to raise the level to the
desired output.
If there were no regulations, that would be the end of it, but since there
are regulations on spectral purity of transmitters, there are resonant
circuits somewhere before the antenna to ensure no spurious frequencies
are transmitted at a significant level.
Below microwave frequencies the resonant circuits are almost always made
of discreet inductors and capacitors forming either band pass or low pass
filters.