i have been quitely following hans' travails on rec.radio.amateur.homebrew
with his digital counter experiments. i dug out a counter from my junk
box. it consists of just a 74HC4020. the output of the fed to the sound
card of my PC. on the PC i wrote an application to count the zero
crossings and multiply the result by 1024. it gave a rough indication of
where my VFOs were. the counting took a second. but it is a rough and
ready instrument. like most amateur intrumentation. but that brings us to
an often overlooked piece of equipment that is present in almost every
shack. the PC.
i know that a number of us cannot live without spice. i haven't figured
out how to use it. but for many of us, designs do start with spice. "can i
spice it?" is a regular refrain on the net. a number of excellent design
tools written by hams are useful around the home lab. i use a large number
of small code snippets to calculate inductances and capacitances from a
test oscillator's frequency readout.
another useful application of the PC is as spectrum analyser workng at
audio frequencies. while this may not seem much at first glance, if you
feed the output of direct conversion receiver to the PC's sound card and
run a DSP software on it, it turns into a fairly useful measurement. for
instance, you can evaluate the crystal filters, tune the front-ends etc. a
half unfinished project at my shack is a spectrum analyser that uses this
principle.
the PC is a powerful a DSP as you can hope to own. the problem is in
getting signals in and out of it. the only available means of doing it is
via audio (baseband). i have used a PC based scope too. but that is a
costly option. costlier than the PC itself. but it might be interesting to
see how useful can the ordinary PC become by strapping some home made
circutis around it.
does anybody have more stories about using PCs in the home lab?
- farhan
