hans is right about the PC being a kludge when compared to an
oscilloscope. I live in India and second-hand oscilloscopes are a
rarity. The new ones cost an engineer's whole year's salary. I have
purchased a tektronix 454 last month on ebay for $300, it is still on
its way to India. So, while i can imagine that in a number of more
developed countries oscilloscopes are not really a problem, they do
remain a problem in many parts of the world.

That puts another angle on it. In that case I'd say you could produce a nice
instrument by using a complete analogue analyser such as my design
http://www.hanssummers.com/electroni...yser/index.htm
or similar, and feeding the sweep (X-axis) and logarithmic output (Y-axis)
into the PC via ADC's on the parallel port. 8-bit ADC's would probably be
marginally good enough, 10 bit for sure.


More often than not, an amateur already has a PC. Adding a simple
hardware to be able to do quick and dirty spectrum analysis might be
an interesting option. As Wes writes in SSD and EMRFD, the purpose of
test instruments is to help with the projects on hand, rather than be
projects themselves (then he went on to homebrewing a spectrum
analyser, hehe).

It became a project in its own right for me. So much that it spawned a
second project
http://www.hanssummers.com/electroni...ser2/index.htm.
But not wasted time - I learnt so much making it and got my first experience
at VHF work etc, so it was time well spent.

Hans G0UPL
http://www.hanssummers.com