[eagle] Path loss (Was: A new opportunity (Phase 4 lite?))

Alan Bloom n1al at cds1.net
Mon Jul 23 09:13:12 PDT 2007


On Sun, 2007-07-22 at 13:17, Rick Hambly (W2GPS) wrote:

> 3) Use 10GHz as the region 1 downlink. This would require a new antenna
> array and we would need to deal with the issues associated with the higher
> path loss while keeping things simple for our average users.

On Fri, 2007-07-20 at 17:42, John B. Stephensen wrote: 
> The increased gain of the earth station antenna compensates for the path 
> loss.

Right.  People say that path loss increases proportional to frequency (6
dB more path loss every time you double the frequency).  But that is
true only if you assume the antenna gain at both ends of the link is
kept constant as you change frequency.

However, if you assume antenna APERTURE is constant with frequency, then
path loss is actually INVERSELY proportional to frequency (6 dB LESS
loss every time you double the frequency).  In other words, for
constant-size antennas, the higher the frequency the better.

So what does that mean for Eagle?

If you assume satellite antenna gain does not change with frequency (so
as to keep the beam width just wide enough to illuminate the earth) and
earth station aperture does not change with frequency (to keep the same
dish size), then path loss is independent of frequency.

Al N1AL




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