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Free Radio Cafe: Pirate Radio On Shortwave & FM • Radio OZNRH says hallo.
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Radio OZNRH says hallo.

Posted: Thu Nov 29, 2012 9:52 am
by RadioOZNRH
Hi here 8-) ..
Here I will describe our MW setup a little closer.

Our transmitter:
Is an 'AMT 3000' in a modified version with 50 ohm 25 mW. output, an linear driver to 1 Watt and finally
a linear PA-stage on 60 Watt PEP. For giving a good music quality, my output from the PA is set to about 10 Watt.
My antenna is a long wire open dipole on 2 x 25 meters wire with matching coils to give a good SWR.

It is planned in the new year we will increase the power to 100 watts, but more on this/when later.
The new 100 Watts PA-stage, is a linear 500-watt level set to 100 Watts RMS in order to provide good space for the modulation. The PA-stage is followed by a 'Diplexer' with harmonic termination and an attenuation of better than -60 dB. of unwanted signals.

My parallel project:

See pic down on the page...

If anyone would like to 'play with', then there is sentenced PWM.

If you do not have a 'PLL signal' available, as shown, the X-tal oscillator can do it.
Power driver is not required for the first test, point 'B' can be connected directly to the test filter 'C'. The construction is not 100% optimized so that there is room for testing and playing.

PWM is a 'newer more economical' way to make AM on when each stage of the transmitter can work quite un-linear as an FM transmitter, remember it is only the pulse width is changing in time with the music not the amplitude, therefore, both Class C and E stages can be used.
Not only that, with PWM can kilowatt transmitters modulated with a few mV. music.
But without a good 'low-pass filter' in the end is not work, because this is here the AM modulation is done.

Let me know if this is something to play with on ;) .

73 from Ole Pirat 8-) ..