"gareth" wrote in message
...
"gareth" wrote in message
...
What is interesting is the simplicity of the approach (ignoring the
hidden
cost of the ubiquitous PC), but it ignores the multiple harmonics that
come out of DDS chips.
So, if you were to working at, say, 3MHz, how would youknow that you were
not actually analysing responses at 6, 9, 12, 15, etc MHz?
MEA CULPA !!!!!
Sorry, but I was thinking out loud about the si570 series of chips and not
about DDS chips.
Ooops!

The other area of befuddled thinking on my part (so many dimensions to such
a project!)
is that when working with a tracking generator, the signal from that
generator is the only
one to have to consider because it will be working in a closed, and largely
shielded circuit,
and that therefore the selectivity of instrumentation will not be
particularly relevant.

Such is the case with the VNWA, where an IF of only 1kHz at frequencies off
several MHz
might at first sight to invite a problem with severe image responses, but,
of course,
with only the one signal in consideration, there cannot be any images!

Anybody out there have experience of input from the sound card via the .NET
framework?

Also, apart from setting up ladder crystal filters, is there any real need
for us to have very
narrow IF filters in our speccy-plus-trackie set-ups?