On Dec 30 2008, 9:41*am, "Tio Pedro" wrote:
"M0WYM" wrote in message

...

I wonder if anyone knows of a project or kit that uses a 'scope timebase
output as the basis of an HF spectrum analyser. My aim is to make something
that would be useful for filter work so I'm not necessarily looking for
very wide frequency sweep.
* Charlie. M0WYM

My own analyzer was a kit for a QST project sold by
A&A Engineering; the design centered around a CATV
module and had it's own timebase and IF strip/log detector
internally. The analyzer used the scope as a X-Y display.
For serious SSB and CW filter work the VCO is going to
be tricky, you'll need low phase noise, etc.; and a good
set of narrow IF filters that can be swept is another
can of worms. *Most of the ham analyzers are better
suited for wider IF responses and wide sweep ranges.
I did a major rework of the IF and Log Amp using an
Analog Devices chip, but the analyzer still has
limitations.

I'd seriously look at some of the DSP receiver kits that
are now on the market--most offer spectrum display
on the computer screen, and adding a good, but
simple, sweep generator might be an easier approach.

Pete

I had a little one band kit radio that was varactor tuned in my hands
for a while and used the sweep voltage from a scope to to drive the
varactors. I was interesting but the scope didnt have enogh
persistence to show a good display. It really looked cool when you
used a marker generator with it in a dark room.

JImmie