LF,
I took the time to draw the circuit of my transmit IQ converter in the
new program i have.
This is the circuit i use to generate my transmit signal to drive the
exciter of my PA. The 137 kHz signal is directly generated in this
circuit. It is mixed with 125 kHz internally.
The basic idea is taken from Andy/G4JNT, tnx agn. The circuit is however
modified for an input frequency of 10.7...12.8 kHz which can be
generated by the soundcard. The 125 kHz generator can be locked to a
reference signal, into a PLL which isn't shown here (separate circuit).
Anyway the circuit is a stand alone device. The input signal level may
be 0 (=100%) down to -30 dB full scale of the soundcard without a change
of the output signal (including a safety factor of > 10 dB).
http://dl.dropbox.com/u/19882028/LF/schematics/TX%20IQ%20converter.png
Comments welcome.
73, Stefan/DK7FC
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