OK! Hans. All right.
Well, meanwhile my VFO is ready, the output waveform is available as a
low impedant rectangular voltage. But i have to choose the caps for
getting and covering the right frequency range.
Yes, Roelof, VFO building is fun, like all that stuff.
Thanks to all for the input! I like the Clapp oscillator.
Here a picture of the D.U.T.:
https://dl.dropbox.com/u/19882028/MF/VFO%20under%20construction.jpg
73, Stefan/DK7FC
Am 05.07.2012 22:44, schrieb hajo.brandt.dj1zb@t-online.de:
Dear Stefan,
Yes. xtal 7,02 MHz will run stable, and xtal 6,5536 MHz must be pulled
down by 12,6 kHz to 6,5410 MHz. A coil in series to the crystal and the
tuning capacitor will do this, in its simpiest form by using a molded rf
choke.
Or 7,0200 MHz is adjusted for 7,0256 MHz, then 6,5536 Mhz will deliver a
difference frequency of 472 kHz. And when 6,5536 MHz is pulled down to
5.6466 MHz, the difference will be 479 kHz.
OK?
73 Ha-Jo, DJ1ZB
"Stefan Schäfer"<Stefan.Schaefer@iup.uni-heidelberg.de> schrieb:
Hello Ha-Jo,
Can you pull one of the xtals to cover the whole band?
73, Stefan
Am 05.07.2012 20:57, schrieb hajo.brandt.dj1zb@t-online.de:
Dear all,
the only parts I have bought so far for MF (still beeing engaged in
other developments) are two crystals: 6,5536 MHz and 7,0200 MHz, to be
mixed with each other. The mixer is another bipolar transistor, and its
emitter current is being keyed. A final source follower after the
low-pass filter will deliver the output to 50 ohms.
The same solution I have also used on LF.
73 Ha-Jo, DJ1ZB
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