# RE: Beginner birds

```> > ...why is the path loss lower in Mode A than in Mode B/J?

The equation for path loss is:

[ 4 * Pi * R ]2
[------------]      Where R is the Range in meters.
[ wavelength ]

So space loss goes down as the square of wavelength.  That is why 10m is
23 dB better, and 2m is 9 dB better than 70 cm and so on.  This
equation is fundamental to all satellite communications.  It is EASY to
transmitted plus antenna gains minus all losses.

Of course, that relationship assumes the SAME kind of antenna as the
baseline (lets say a dipole).  It is obvious when you think about it
because as Tony said, a 10m dipole collects the signal from 200 times
more area then a 70 cm dipole.

But conversly, it is EASIER to get high gain as you go up in frequency.
In fact you get it all back if your antennas cover the same AREA.  Thus
a 10' TV dish will have the SAME link budget to a satellite using an
OMNI antnenna no matter what frequency is used... (within reason
Usually it needs to be 10 wavelengths across ore more))...

Tony said it this way...

> The capture area increases as the frequency is lowered.  2m has 9x the
> capture area of 70cm, and 10m has over 20x the capture area of the