Text 75, 66 rader
Skriven 2005-07-15 14:16:06 av Herman Trivilino (1:106/2000.7)
     Kommentar till text 74 av Sean Dennis (1:18/200)
Ärende: FM Capture Card
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 SD> I'm really enjoying this conversation: it's nice to see some
 SD> traffic in here. :)

Yup. It sure beats trying to get a signal amongst all the noise on Usenet.  The
role played by noise makers might be essential in keeping an echo alive,
though.  But that's a topic for a whole nother discussion ;-)

 SD> I've seen the FM loops, but never used one.  To be very
 SD> honest, I'm not sure of the big difference and now my
 SD> curiosity gets me.

Take a look at radio snack's 42-2385 (Dipole FM Antenna).

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=42-2385

I've got one out in my laboratory (er .. sorry, my garage).  I'll do a
continuity test on it.  Yup.  It passes.  I've made antennas like this before
using the old 300-ohm antenna wires that we used to run to our TV antennas
before the advent of cable-tv.  In fact, I have one in my attic connected to
the receiver of my home-theater/entertainment center.  I live 25 miles from the
center of Houston, Texas, so there are plenty of stations well within range and
this antenna performs ok.  I've always desired something a bit better, though.

This one just caught my eye while I was browsing www.radioshack.com.

15-2163 (High-Gain FM Stereo Antenna).

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=15-2163

The price looks good, too.

 SD> I'm wondering what the loop would do-be better grounded?

I'm thinking about the standing waves present in the antenna.  Without the loop
you've got a displacement node at each end of the antenna.  This would be, I
guess, what you'd call a half-wave antenna?  Let's see, if 16 ft is half a
wave, then the wavelength is 32 ft, or about 10 meters.  That's pretty close,
isn't it, to the lenght of a wave in the FM band?

Let's see ... A typical FM station is 100 MHz, or 100 000 000 Hz.  For a
wavelength of 10 meters we get a wave speed of (100 000 000 Hz)*(10 m) = 1 000
000 000 m/s.  So, that's the same order of magnitude as the speed of
electromagnetic waves in a vacuum (300 000 000 m/s).

 SD> Now if I can just learn to work on computers and not release
 SD> the smoke they run on every so often, I'll be good. <G>

Yup.  You gotta keep that magic smoke contained within the circuitry.  Let it
out, and it's all over!

If you decide to take some classes you might want to hang out in the physics
department and see if you can help set up the laboratory.  It's a good way to
get some inside info on what's what -- which courses and profs are better, and
stuff like that.  Of course, a 4-year school isn't going to have the hands-on
computer courses that you might be interested in.  You'd have to go to a 2-year
school for stuff like that.  They have physics departments, too, and love to
have help setting up the laboratories.

I'll let you know how my antenna adventures come out.

Thanks for the advise.

Herman

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 * Origin: Big Bang (1:106/2000.7)