Okay, I'm thinking about parabolic antennas right now. I created a
spreadsheet that would take care of all the formulas some years back but
I can't seem to find it now. I'm trying to find all the formulas that I
need to get the information I need to make my brain figure out the
resolution at a distance based on dish size and frequency receiving. So
I don't have to remember this, again, I'm writing it down here.
- The formula Ψ = 70λ/D creates an estimate for the beamwidth of half
the power (to -3dB of the signal).
- A larger parabolic antenna will yield a smaller beamwidth which
should result in a higher resolution.
- As frequency goes up the beamwidth goes down.
I'll use a 1m [diameter] dish as a reference since that size isn't too
large for personal use.
This provides the basis of receiving a signal from a distance. But the
other question to look at is how big is that signal that you are looking
for. If you are trying to communicate with another terrestrial station,
or even an orbiting station, then having equal footing is great as there
is no waste. This hardly happens and the antenna usually ends up trying
to pull in a weak station and also gathering the surrounding noise.
But what if I'm not trying to communicate with another station but
rather trying to hear a tiny "voice" in the middle of trillions of other
voices? I'd want a very tight beam to be able to not only pull out that
tiny voice but also not collect the surrounding voices (and not
overwhelming my receiver with a high noise floor). The vocabulary
escapes me at this point. I'm sure there is a word for it but all I can
come up with are words that describe optical reception (e.g. pixels and
resolution). When I can figure out the vocabulary and the formulas
needed to put these two puzzle pieces together I'll post it here.