On Mon, 24 Jan 2005 00:10:08 +0000 (UTC), "James Bond"
wrote:
i'm after a circuit for a 2m VCO.
basically i'm planning to homebrew a kind of tracking generator, where I can
sweep across 2m to look at filter shapes, etc.
my plan is to sweep, using a vco, across 2m using a sawtooth waveform. this
waveform will also be amplified and fed to an oscilliscope, to give me a
horizontal sweep.
the output from the filter will then be fed to a RF millivoltmeter circuit
(again, anyone got any good circuits?) and this will then be fed into a
logarithmic converter then be put onto the Y deflection, to give me
amplitude.
That's called a spectrum analyser ...
calibration will be by putting the system into "manual" mode and connecting
to a frequency counter, then sweeping up and down until get specific
frequency, then the x-centering be used to set this on a known point.
Another way to provide cal information is with a comb generator. Add a
controlled amount of this to your detector input and you get blips on the screen
at comb spacings. Obviously have this switchable.
basically anything that having say 1-6V in giving a 140 to 150mhz sweep
would be grand, then i can play with amplifiers to get it just as i want.
Pinch the Tx VCO out of a highband mobile.
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