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From YouTube: Space and Satellite Symposium 2021 Jan King
Description
Space and Satellite Symposium 2021 Jan King
A
Good
morning,
good
afternoon,
I'm
jan
king
and
w3
and
vk4gui,
and
I'm
speaking
to
you
this
morning
from
near
noosa,
queensland,
australia.
So
a
little
further
away
than
some
of
you
been,
and
today
I
wanted
to
talk
about
future
projects
and
fun.
We
can
do
with
millimeter
wave
communications
and
particularly
when
I
say,
millimeter
wave,
I'm
referring
to
frequency
bands
really
between
about
10
and
about
50
gigahertz,
because
those
are
the
practical
bands
that
we
can
do.
A
A
But
we
have
two
bands,
10
and
24
that
are
50
megs
wide
and
then
one
at
at
47
gigahertz,
which
I
think
is
the
jewel
in
the
crown
for
us
all.
If
you
imagine,
we
have
four
megahertz
of
spectrum
that
we
have
available
to
us
in
the
two
meter
bands
which
those
of
you
or
radio
amateurs
know
is
very,
very
heavily
used
around
the
world
and
is
very
popular.
A
Imagine
that
up
at
47
gigahertz,
we
have
200
megahertz
of
spectrum,
so
think
of
what
we
could
in
fact
actually
do
in
terms
of
moving
data
with
such
an
awesome
amount
of
spectrum.
When
you
look
at
the
table,
47
to
47.2
doesn't
seem
like
very
much
spectrum.
It's
only
a
small
fraction
of
the
absolute
frequency,
but
actually
200
megahertz
is
awesome.
A
The
an
important
thing
to
point
out
is
we
now
have,
while
the
one
of
the
reasons
we
haven't
been
using.
These
bands
and
larger
numbers
of
people
is
because
only
specialists
who
are
really
very
excited
about
using
microwave
communications
have
ventured
into
the
process
here,
because
working
with
equipment
is
a
lot
harder
to
do
and
it
hasn't
been
readily
available.
A
So
it's
the
ionosphere
that
rules
at
hf,
whereas
at
shf's
or
millimeter,
wave,
depending
on
which,
how
you'd
like
to
talk
about
it,
the
atmosphere,
rules
and
particularly
the
weather
rules,
and
particularly
in
most
in
most
of
the
bands
we're
talking
about
today.
It's
it's
it's
rain
or
water.
That
causes
the
problem
and
the
fun
and
so
water
from
the
atmosphere
absorbs
rf.
It
sums
it
doesn't
somewhat
selectively
due
to
the
quantum
mechanics
of
of
the
various
molecules
of
nitrogen
oxygen
and
water
and
carbon
dioxide
that
exist
within
the
atmosphere.
A
A
But
before
we
can
play
in
these
games,
we've
gotta
first
pay
as
it
were,
and
when
I
mean
pay,
we
mean
we
need.
We've
got
some
work
to
do.
We
need
to
figure
out
how
we're
going
to
share
the
radio
spectrum
with
others
and
we'll
talk
about
that
in
the
next
few
slides,
but
we
also
need
to
do
a
bit
of
research.
A
So
how
can
we
share
with
other
services
at
10
and
24?
Gigahertz
is
particularly
important
because
those
two
bands
are
going
to
be
the
most
important
ones
to
start
with
and
then
we'll
phase
into
47.
I
I
would
forecast,
because
that's
a
little
bit
harder
because
of
the
high
propagation
losses,
excess
path
losses
that
you
get.
A
I
would
say
that
about
every
three
months,
new
parts
are
coming
on
on
the
market
from
5g
cellular
primarily,
but
that
will
cover
these.
The
frequency
range
that
is
associated
with
with
these
two
bands
and
gallium
nitride
in
particular,
as
a
as
a
power
technology,
is,
is
increasing
so
fast
that
we
will
be
at
several
watts
of
power
by
the
time
we
get
into
this
very
far
so
device
efficiencies
and
device
frequency
range
ranges
are
are
ever
ever.
A
Trending
upward,
the
the
other
thing
is
how
bad
are
the
xf
path
losses
at
24
and
47
gigahertz
we're
going
to
talk
about
that
a
bit,
but
we
still
need
to
characterize
that
on
a
local
level.
So
wherever
you're
located
you'll
need
to
know-
and
you
will
learn
about
that-
it's
the
basic
thing
you'll
be
a
lot
smarter
about.
Is
the
excess
path
loss
on
these
two
frequency
bands?
A
A
It's
from
a
u.s
government
version
because
you
see
on
the
left
at
the
top
is
the
international
part
of
the
table,
which
has
regions
I.t
regions,
one
two
and
three,
and
what
we
see
is
that
what
the
us
is
doing
with
that
nurse
you
may
know
the
us
uniquely
has
both
a
government
and
a
non-government
side
each
controlled
by
a
separate
agency.
The
federal
government's
controlled
by
the
ntia
in
the
in
the
non-federal
part
like
us
is
controlled
by,
of
course,
the
fcc.
A
But
when
you
look
at
these
tables,
you'll
notice
that
the
nice
thing
is
that
we
have
amateur
radio
worldwide
in
all
three
regions
in
this
10
gigahertz
fan,
which
is
in
a
way
we've
already
been
using
it
there's
already
a
couple
of
satellites,
including
oscar
100,
which
is
a
is
a
geo
spacecraft
that
uses
the
10
gigahertz
band.
I
believe,
but
it
is
only
given
to
us
on
a
secondary
basis,
both
amateur
and
amateur
satellite,
but
you'll,
see
in
addition
to
these
assignments
or
allocations
in
the
regions.
A
You'll
see
that
there
are
some
funny
little
numbers
at
the
bottom
of
the
of
this
of
this
table
and
those
are
of
course
footnotes
and
the
footnotes
are
both
national
and
international.
I
think
you
can
look
at
it
and
see
which
are
the
number
ones
are,
of
course,
international
and
then,
where
it
says,
u.s
128,
that's
clearly.
National
ng
means
non-government.
A
A
This
is
sometimes
called
a
metoo
and
as
michelle
and
I
laughed
yesterday,
when
you
see
a
me
too
footnote
where
lots
of
countries
are
listed,
the
first
country
listed
is
is
non-alphabetical,
you
notice
knows
it's
germany,
so
it
means
germany
created
this
footnote
and
then
everything
else
is
in
alphabetical
order.
Those
are
the
metoos.
A
Those
are
the
guys
that
jumped
on
the
footnote
during
a
world
radio
conference
and
said
we'd
like
to
do
this
as
well,
and
then
it
becomes
a
law
and
5.481
is
the
law
and
what
you'll
notice
here
I
underlined
the
last
part
because
it
says
that
these
this
spectrum
is
allocated
to
these
countries
for
fixed
and
mobile
use.
Now,
that's
pretty
broad
and
it's
pretty
in
it
means
it's
pretty
intense
telecommunications
services.
A
The
mobile
could
even
be
cellular,
although
I
don't
think
this
band
is
used
anywhere
in
the
world
for
cellular,
it's
some
kind
of
mobile
service
and
it's
on
a
primary
basis.
So
what
that
means
is
that
in
these
countries
this
ban
to
amateur
radio
is
secondary
to
all
these
primary
mobile
and
fixed
services
that
are
being
talked
about
here,
and
that
really
is
a
potential
problem.
What
it
really
means
is
that
these
countries
listed
probably
don't
have
amateur
radio
in
the
domestic
table.
A
If
you
look
at
their
domestic
table
of
frequencies,
they
don't
assign
amateur
radio.
Most
of
these
countries
will
not
assign
image
radio
at
all
in
that
frequency
band.
So
when
we
launch
a
satellite,
let's
say
to
support
this
frequency
band,
we'd
have
to
realize
that
these
countries
are
countries
that
won't
be
allowed
to
communicate
through
that
device.
A
Another
interesting
point
here
is
that
there
are
other
priorities
implied
by
the
footnotes
and
the
ng
51
at
the
bottom
is
telling
us
that
we're
actually
higher
ranking.
While
we
make
what
may
be
much
lower
than
the
the
the
people
who
have
assigned
on
to
the
4.58
5.481
were
higher
than
a
certain
class
of
non-government
users
who
are
using
radar
in
this
ban.
A
That's
that's
the
the
radio
location
in
capital,
letters
within
the
table,
but
for
non-government
users
in
the
us
we
have
priority
over
them.
So
it's
kind
of
a
mismatch,
but
it
shows
you
how
complex
frequency
assignments
can
be
and
why
you
need
to
read
the
little
numbers
at
the
bottom
of
the
table
when
you're
looking
at
this
and
sorting
out
what
what
it
may
mean
to
you.
A
And
if
you
just
look
at
this
it,
it
looks
like
we're
the
only
people
in
the
band
except
there's
that
funny
little
number
at
the
bottom
again.
So
we
have
to
go
look
up
5.150
and
when
we
do,
we
see
that
a
bunch
of
bands
are
influenced,
including
this
one,
by
the
fact
that
those
are
also
set
aside
for
industrial,
scientific
and
medical
forget
about
those
that
terminology
and
just
think
wi-fi
and
bluetooth,
and
anything
else
that
makes
a
lot
of
racket
in
the
in
the
two
gigahertz
band.
A
You'll
see
that
our
our
s,
band
frequency
2400
to
2417
is
us
is
within
that
24
25
100
and,
of
course
we
know
what's
happening
in
that
frequency
band.
It
is
full
to
the
brim
with
wi-fi.
Everybody
everywhere
is
using
it
for
connecting
their
computer
to
devices
all
around
the
house.
So
24
gig
could
become
like
that.
A
A
Footnotes
in
the
in
the
itu
table
of
allocations
and
the
the
radius
terminals
are
very
good
at
that,
so
the
best
way
for
us
to
protect
radio
astronomy
would
be
if,
when
we're
transmitting,
we
don't
transmit
with
something
that's
up
in
the
air
like
an
aircraft
or
balloon
or
a
spacecraft,
because
that
causes
restaurant
radio
astronomers,
of
course,
a
lot
more
difficulty
if
they're
trying
to
discriminate
between
something
that's
up
in
the
sky,
which
is
their
home.
After
all,
all
their
antennas
are
pointed
up
in
the
sky.
A
So
it's
better
if
we
were
to
transmit
from
the
ground
where
there's
lots
of
things
that
absorb
signals
on
the
ground
and
good
chance,
we're
going
to
be
far
away
from
a
radio
astronomy
site,
whereas
the
satellite
is
going
to
be
a
lot
of
the
time
in
view
of
radio
astronomy
sites.
This
is
all
saying
that
between
those
two
footnotes,
it's
best
if
we
use
this
van
as
an
uplink
band,
because
we'll
cause
the
radio
astronomers
less
grief
and
also
the
interference
that
we
might
receive
from
something
like
wi-fi
stations
won't
matter.
A
A
A
A
A
Okay,
so
we've
we've
talked
about
the
the
nastiness
of
spectrum
management
here
with
respect
to
these
bands.
Now
I
think
another
fun
thing
to
look
at
is
how
how
are
these
bands
different
than
what
we've
done
in
the
past
and
how
we've
used
radio
spectrum
and
how
we've
used
how
we
built
our
radios
in
the
past?
Well,
the
first
thing
to
look
at
is
for
each
of
these
frequency
bands.
How
hard
is
it
to
actually
get
a
signal
from
one
point
to
another?
A
There
are
wetter
places
in
africa,
but
this
is
pretty
bad.
So
if
you
look
at
what
being
bad
in
the
case
of
the
absorption
of
rf
energy,
then
this
is
the
condition.
This
is
what
you
would
see
if
you
had
a
satellite-
and
you
were
passing
a
signal
from
that
satellite
in
either
direction.
You
could
be
transmitting
to
it
or
receiving
it,
but
it's
passing
through
the
atmosphere
at
an
elevation
angle
to
this
to
the
earth
station
or
the
receiving
station
anyway,
at
10
degrees
elevation
and
I'm
using
a
one
meter.
Diameter
dish.
A
You
notice
we're
only
talking
about
the
the
absorption
here,
the
local
excess
pap
attenuation
that
we
get
in
the
signal,
so
you'd
say
well.
Why
does
the
size
of
the
dish
matter?
Well,
the
itu,
when
it
figures
all
the
all
the
problems
that
cause
absorption
it
considers
one
called
scintillation
and
scintillation
is
a
rapid
rapid
variation
in
the
signal,
strength
and
the
it
decided.
It's
just
going
to
pretend
that
that's
like
a
loss.
A
If
you
have
2
db
of
variation
in
the
signal
strength,
it
assumes
that
that
variation
can
be
applied
as
a
loss
to
the
signal
and
because
this
variation
is
occurring
in
the
atmosphere
itself,
the
the
larger
the
collecting
device
that's
receiving
it,
the
bigger
the
aperture
of
the
antenna,
the
more
scintillation
energy
is
collected
so
when
it
calculates
the
amount
of
scintillation
to
add
in
here.
So
that's
another
point
to
make
here
and
that
is
that
I'm
using
for
this,
these
tables
you'll
see
the
itu-p-618
rain
model.
A
It
happens
to
be
revision.
Six,
if
that's
of
interest
they're
up
to
revision.
Nine.
I
think
now
or
something
like
that.
But
anyway,
this
is
this
is
from
the
itu
and
it
calculates
the
effects
of
the
atmosphere
rain.
If
there's
is
any
carbo
other
gas
absorption
like
carbon
dioxide,
it
would
calculate
that
and
scintillation
losses.
It
also
accounts
for
water
absorption
differently
between
clouds
and
just
normal
water
system
suspended
in
the
air
and
then
rain
itself.
So
each
of
those
is
considered
a
separate
category.
A
It's
it's
a
good
reference
because
they
these
are
measurements.
These
observations
have
been
carefully
documented
and
collaborated,
and
then
I
think
boulder
colorado
is
the
moderate
location,
because
the
ma
the
rain
there
is
moderate,
but
more
more
than
that,
it's
one
of
the
most
measured
places
on
the
planet
when
it
comes
to
meteorology,
as
many
will
know.
A
So
what
you
see
is
that
at
10
gigahertz
there's
not
too
much
difference.
We
really
haven't
gotten
to
the
point
where
water
is
becoming
totally
substantial,
but
we
are
getting
at
10
gigahertz
averaged
about
a
db
over
all
these
locations,
we're
getting
a
db
of
extra
path
loss
in
addition
to
the
one
over
r
squared
path
loss.
You
get.
You
always
get,
no
matter
where
you
are.
A
If
we
go
up
to
the
24
gate,
band
24
gigs
is
actually
on
a
slight
local
peak
in
the
water
vapor
absorption.
There
is
actually
a
resonance
phenomenon
occurring
in
a
water
vapor
molecule
that
the
response
at
24
gigahertz-
it's
not
huge,
but
it's
big
enough
to
take.
Take
new
orleans
from
one
and
a
half
db
up
to
about
nine
db-
and
this
is
this-
is
this
by
the
way
is
under
conditions
where
there's
no
rain.
A
A
Sadly,
when
we
go
up
to
47
gigahertz,
the
band
we'd
like
to
most
use
in
a
way
because
it's
ours
and
the
reason
it's
ours
is
because
nobody
else
wanted
to
deal
with
this
stuff.
So
they
said
all
the
hams
will
do
this,
we'll
give
it
to
them
so
anyway.
So
we
we've
got
what
case
of
11db
for
new
orleans
and
it's
not
too
different
at
that
frequency
between
svalbard
and
boulder,
but
it
sure
is
going
to
hit
us
hard
at
any
place
in
the
world
where
it's
wet.
A
A
With
99
rain
conditions,
the
absorption
has
gone
up
significantly
at
new
orleans
up
to
three
db
at
10
gigs.
But
heavens,
if
we
look
at
47
megahertz,
if
ever
there
was
a
brick
wall,
81.7
db
is
such
a
brick
wall.
What
that
means
is
somebody
in
new
orleans
can't
talk
across
the
block,
let
alone
out
to
space.
A
In
the
modern
case
for
boulder
26.9
db
at
47,
gigahertz
isn't
a
total
deal
killer,
but
what
it
would
mean
is
that
if
you
had
a
one
watt
transmitter
and
were
able
to
communicate
with
the
rain
off,
you
would
be.
You
would
have
to
have
about
a
500
watt
transmitter
to
be
able
to
transmit
with
the
rain
on.
So
that's
a
pretty
pretty
big
hill
to
climb,
to
say
the
least.
By
the
way
you
can
not
only
increase
your
power
here.
You
could
also
increase
your
antenna
gain.
A
So
if
you
wanted
to
make
yourself
a
four
meter
dish
or
something
like
that,
and
do
this
it'd
be
a
little
bit
difficult
to
point,
because
it
would
be
under
0.1
degree,
beam
width,
but
on
the
other
hand,
that
would
help
you
reduce
your
power
okay.
So
what
we
know
is
that
if
we
have
the
rain
on
for
these
frequency
bands
it
it
gets
pretty
dire.
A
Even
at
24
gigahertz,
it's
getting
pretty
dire,
but
one
thing
we
can
do
to
improve
things
is:
if
we
do
have
a
satellite,
we
can
move
the
satellite
up
in
the
sky
for
the
case
of
our
analysis.
So
so,
let's
assume
we
now
have
a
spacecraft
which
is
and
we're
going
to
talk
a
little
bit
but
not
much
about
orbits
at
all
today,
but
we're
going
to
put
this
spacecraft
in
an
orbit.
A
That's
pretty
far
out
there
it's
going
to
be
out
as
far
as
a
geostationary
satellite
and
at
it's
at
it's,
it's
it's
going
to
be
in
an
orbit
that
comes
close
to
the
earth,
but
most
of
the
time
it's
going
to
hang
out
near
the
apogee
of
the
orbit
and
when
it's
out
there
the
earth
is
going
to
rotate
under
it.
So
sometimes
you're
going
to
have
really
good
elevation
angles
and
what,
if
you
did
have
a
70
degree,
elevation
angle
and
a
spacecraft
hanging
out
there?
A
Gigs
is
still
not
a
problem
for
us,
but
it's
it's
not
entirely
undoable
and
what
we
can
also
say
is
well
90.
This.
This
condition
is
only
going
to
last
one
percent
of
the
time
and
99
of
the
time
it's
going
to
be
better
than
that.
So
what
it
says
is
that
for
for
a
wet
place
like
new
orleans,
47
gigahertz
at
high
elevation
angles
is
going
to
be
a
really
fun
weather
monitoring
system.
A
You
can
really
tell
how
bad
the
weather
is
by
just
listening
to
how
weak
a
beacon
would
be
from
a
spacecraft
or
a
distant
a
distant
mountaintop
set,
but
it
shows
that
there's
a
lot
of
fun
to
be
had
by
learning
about
weather
here.
At
svalbard
we
see
that
at
70
degrees
pretty
much.
We
don't
have
to
worry
in
a
very
dry
place
about
the
spectrum,
as
the
elevation
angle
gets
higher
and
for
boulder
it's
more
of
a
challenge
at
47
gigs,
but
it's
kind
of
an
in-between
case.
A
So
how
could
we
best
use
these
bands
given,
given
these
various
absorption
characteristics
and
given
the
bunch
of
footnotes
we
had
so
satellites,
typically
relay
signals
between
two
locations
on
the
earth?
That's
hopefully
easy
to
understand
and
in
doing
that
they
commonly
have
some
kind
of
electronic
repeating
device,
so
there's
an
uplink
frequency
in
the
downlink
frequency
channel
and
and
so
that
the
downlink
doesn't
interfere
with
the
uplink.
A
Typically,
these
two
frequency
bands
are
different
in
frequency
from
one
another,
usually
by
about
at
least
10
percent,
sometimes
as
much
as
50
percent,
but
quite
different
from
one
another.
So
we
can
use
filtering
to
filter
the
the
downlink
signal
and
make
sure
that
none
of
that
energy
gets
into
the
uplink
band,
because
there's
probably
160
170
db
difference
between
the
levels
of
those
two
signals.
A
And
we
take
into
account
here
that
amateur
radio
as
it's
it's
evolved
in
our
society.
Radio
amateurs
have
always
wanted
to
listen
to
another
signal,
even
more
than
they
really
need
to
talk
back
to
that
source.
So
the
whole
idea
of
shortwave
listening
was
the
first
case
where
people
used
to
listen
to
signals
before
radio
amateurs
before
they
became
radio.
Amateurs
got
hooked
on
the
hobby
because
they
were
listening
to
signals,
and
they
said
oh
I'd
like
to
do
that
too.
A
So
because
of
that,
we
want
to
make
sure
that
the
downlink
is
always
more
more
accessible
to
us
than
than
the
uplink
is,
which
says
that
we
want
to
be
able
to
make
sure
the
downlink
is.
Is?
Is
the
easiest
thing
about
a
radio
system
to
to
hear
or
or
to
listen
to?
Some
people
would
say
to
a
lot
of
people?
Don't
listen
anymore
with
their
ears,
so
we're
talking
about
dated
data
streams.
A
A
We
talked
about
it
a
little
bit
already
is:
we've
got
to
protect
the
radio
astronomers,
and
we
also
have
wi-fi
in
that
band
or
all
manner
of
different
signals,
including
wi-fi,
are
going
to
appear
and
things
that
haven't
yet
been
invented
are
going
to
appear
in
that
band.
So,
for
that
reason,
where
there's
going
to
be
a
high
local
interference
level
and
you
can't
protect
against
it-
we've
tried
many
times
to
make
that
work
at
s-band
at
2.4,
gigahertz
and
we've
been
very
unsuccessful,
there's
always
local
interference
and
it
can't
be
eliminated.
A
It's
coming
in
the
sidebands
of
even
very
directive
antennas,
so
the
that
all
points
to
the
fact
that
24,
it
is
a
natural
uplink
band,
and
we
should
be
thinking
about
that
as
we
move
forward
at
least
for
satellite
use,
if
it,
if
you're
using
it
for
terrestrial
use.
There
are
problems
that
can't
be
overcome
because
of
wi-fi.
A
A
A
So
by
all
rights.
This
means
we
should
make
it
a
downlink
ban,
because
if,
if,
if
we
don't
have
any
constraints-
and
we
don't
have
to
protect
other
services,
go
for
it,
we
should
have
it
high
up
in
the
sky
and
and
downlink
as
much
power
as
we
can
and
with
200
megahertz
there's
room
to
do
anything.
Any
reasonable
person
would
like
to
do.
A
A
So,
if
we
think
of
those
in
the
way,
I
suggested
it
a
for
a
spacecraft
system,
a
transponder
that
evolves
might
a
modern
day.
Transponder
might
look
something
like
this,
so
the
we.
If
we
want
to
take
24
gigahertz
as
being
our
uplink
band,
for
the
reasons
that
have
been
described,
then
we
could
have
a
dual
frequency
receiver,
where
we
had
a
47,
gig
uplink
and
a
24
gig,
and
we
would
probably
for
a
spacecraft,
use
something
like
a
horn
antenna.
A
We
don't
want
to
go
a
lot
into
spacecraft
technology
here.
Right
now
could,
but
I
don't
think
we
should,
and
what
I
would
say
is,
though,
at
the
apogee
of
the
earth
at
the
apogee
of
an
orbit
like
this,
which
is
a
geotransfer
orbit,
is
what
we're
proposing
you're
at
an
altitude
of
about
36,
000
kilometers,
and
if
that
altered
to
the
earth's
about
18,
19
degrees
in
size
and
so
the
antenna
you
would
want
to
match
that
beam
width
is
somewhere
between
17
and
22
db.
A
So
all
these
antennas,
if
you
want
them
to
be
your
coverage,
so
everybody
on
the
earth
could
participate.
Then
that's
about
the
gain
you
want
for
these
antennas
and
then
you
have
to
make
up
the
rest
of
the
game
that
you
need
between
the
uplink
and
the
downlink
through
to
the
various
receiving
and
transmitting
elements
of
the
transponder.
A
But
anyway
we
end
up
having
a
dual
frequency
receiver
and
we
that
would
also
include
some
down
conversions.
So
we
convert
to
some
if-ish
channels,
I'm
just
calling
them
here,
generically
channel
one
and
two
that
would
go
into
a
software-defined
radio
or
and
in
a
specific
example,
the
software-defined
radio
that
we
might
use
would
be
some
of
the
technology.
That's
out
there
that
various
vendors
are
putting
forward
called
an
rf
silicon
on
chip
device.
So
an
rf
socket.
These
things
come
in
lots
of
flavors
and
lots
of
frequencies.
A
A
lot
of
them
will
at
least
support
ifs
up
to
about
six
gigahertz,
and
I
think
even
the
crummiest
ones
are
down
around
s
band
around
two
gigahertz.
So
you
would
have
a
couple
of
channels
carrying
and
each
of
these
channels
by
the
way
could
contain
multiple
users.
So
you
might
call
those
sub
channels,
so
each
each
user
might
be
side
by
side
in
the
spectrum
you
might
use
tdma.
A
You
might
use
code
division,
multiple
access,
however,
you
do
the
multiple
user
game,
it's
done
by
this
dual
frequency
receiver
and
convert
it
to
two
data
streams
channel
one
and
channel
two
into
the
software
defined
radio,
amplification
and
demodulation,
and
maybe
even
data
storage.
So
you
might
have
tied
to
this
software
defined
radio,
a
large
memory
where
we
could
store
minutes
to
hour
seconds
to
hours
of
data,
and
then
we
might
play
back
through
the
downlinks
on
channel
one
and
two.
A
Now
that
the
downlink
situation
would
be
that
we
would
have
a
downlink
at
10.5
gigahertz,
as
we
said,
and
for
experimental
purposes,
we'd
also
put
a
downlink
at
47
gigahertz.
Now,
since
we
know
we
need
a
fair
amount
of
separation
between
the
uplink
and
the
downlink,
we
already
know
that
we
might
have
a
situation
where
the
47
gigahertz
receive
and
transmit
certainly
can't
be
on
the
same
frequency
and
be
both
on
at
the
same
time.
That
would
be
kind
of
bad
juju.
A
So
we
would
either
need
to
time
multiplex
these
in
some
way
or
either
either
in
a
short
term
basis
like
on
the
millisecond
level,
or
we
might
do
it
by
saying
well
right
now
we're
going
to
have
the
47
gigahertz
receiver
on
and
an
hour
from
now
we're
going
to
put
the
47
gigahertz
transmitter
on
and
then
we'd
have
various
modes
between
the
uplinks
and
the
downlinks.
We
could
support,
but
clearly
we
couldn't
have
both
47
gigahertz
radios
on
at
the
same
time.
That
would
work.
A
We
talk
about
the
whole
system.
This
satellite
would
be
a
gto
like
orbit,
so
it
has
a
perigee
down
low.
Maybe
we
take
it
up
a
little
bit,
so
it's
up
around
a
thousand
kilometers
1200
kilometers,
something
like
that
and
then
the
apogee
goes
up
to
this
magic
number,
which
is
the
geo
altitude.
By
the
way,
the
way
you
catch
a
ride
is
to
is
to
ride
with
geo
spacecraft,
which
exactly
goes
to
this
orbit.
A
Already
all
we'd
be
doing
is
getting
off
the
geo
bird
or
the
the
platform
attached
to
the
geo
bird,
the
upper
stage
of
the
of
the
launch
vehicle,
and
then
we
might
have
enough
delta
v
on
board
our
little
satellite
to
just
increase
the
perigee
a
little
bit.
It
doesn't
take
much
delta
v
to
do
that.
The
transponder,
as
we
said,
would
be
in
as
shown
here.
A
44
dbw
is
over
over
ten
thousand,
it's
it's
more
than
twenty
thousand
watts
of
effective
isotropic
radiated
power,
but
it's
all
because
of
the
antenna
of
course,
and
we
have
to
pass
through
the
atmosphere.
We're
gonna
have
a
clear
sky
case
here,
so
the
sun's
out
we're
just
passing
through
the
layers
of
the
atmosphere
there
and
what
happens.
A
Is
we
end
up
with
a
signal
if
we
look
at
the
upper
part
of
this
figure,
where
there's
two
measures
of
goodness
that
I've
defined
c
over
n
plus,
I
means
the
carry
to
noise
plus
interference
ratio.
It's
the
same
as
the
signal
and
noise
ratio.
The.
I
is
just
noting
that,
in
addition
to
white
noise,
you
may
have
other
forms
of
interference
that
you
collect
on
the
way
up
to
the
spacecraft,
and
so
it
accounts
for
that,
and
then
the
number
I
like
is
the
c
over
n
zero.
A
A
Realizing
the
signals
have
such
an
extraordinarily
high
path
loss,
we're
losing
just
due
to
one
over
the
distance,
squared
we're
losing
212
db
on
the
way
out
to
a
geo
altitude
spacecraft
that
212
db
is
hard
to
get
back
even
with
the
gain
a
gain
on
both
ends
of
the
link.
So
we've
got
about
20
some
db
of
gain
in
the
satellite
we've
got
like
40
some
db
of
gain
on
the
ground
station
and
that
60
db
combined
isn't
enough
to
do
the
trick.
A
We
also
need
to
make
sure
that
we're
transmitting
we're
demodulating
with
the
best
possible
methodology
we
we
can.
So
we
we
not
not
only
use
forward,
error,
correction
coding,
we
use
forward
error
correction
coding
twice
and
when
we
do
that
the
data
rate
we
can
get
on
this
10
kilohertz
wide
channel
is
about
15.6
kilobits
per
second.
A
A
Now,
if
we
look
at
the
downlink,
we
we're
down
to
10
10.5
gigahertz,
and
you
see
the
path
loss
has
gone
down
to
about
205
db,
so
it's
a
little
less
difficult
to
get
the
rf
down
and
that's
why
we
put
the
down
link.
That's
one
of
the
reasons
we
put
the
down
link
here
and
the
excess
path
loss
is
also
pretty
low.
It's
only
a
db.
A
So
that's
already
worth
talking
about
a
little
bit,
because
10
watts
of
rf
power
at
a
little
satellite
is
not
so
easy,
really
because
it
means
with
the
efficiency
of
something
like
gallium
nitride.
We
need
about
35
watts,
30
watts,
and
if
we
have
some
other
radio
equipment,
we
might
need
about
40
watts
of
rf
of
dc
power
to
support
that
10
watts
of
rf.
A
So
that's
not
a
totally
unbelievably
cheap
satellite,
we're
probably
talking
the
better
part
of
a
million
dollars
for
a
spacecraft
like
that
in
this
day
and
age,
and
you
know
you
might
need
to
pay
another
half
a
million
to
get
a
ride,
so
not
totally
cheap.
But
it's
it's.
What
we
got
to
do
to
make
this
happen
if
we
put
the
clouds
in
there.
A
Oh,
I
didn't.
I
didn't
give
the
results
here.
The
data
we
then
achieved
now.
What
we're
doing
is
we're
taking
all
of
those
users
and
we're
providing
a
common
downlink
which
is
shared
by
all
the
users.
So
all
the
users
receive
a
wider
band
signal.
Now
this
this
signal
is
in
a
one,
megahertz
bandwidth
and
it
again
uses
dvds2
and
double
coding
forward
air
correction
coding,
and
if
we
we
do
that,
we
we
can.
A
A
I
tried
to
think
of
a
lot
of
fun
things
we
could
do
so.
Of
course
we
could.
We
can
talk
text,
send
data
files
and
anything
else
you
can
pretty.
Well.
Imagine
that
that's
defined
by
betw,
roughly
10-ish
kilobits
per
second
around
the
world,
and
we
can
do
it
for
many
hours
a
day,
even
with
john
one,
gto
type
high
earth
orbiting
satellite
that
we
get
from
re-harvesting
a
a
geo
satellites
launch
vehicle
with
six
such
satellites,
which
would
be
a
goal.
A
A
A
Is
that
a
deal
killer
for
for
this
band,
and
we
can
compare
it
to
the
24
gig
band,
which
is
already
something
we'll
we'll
know
more,
we'll
learn
more
about
24
gigahertz
before
we
ultimately
learn
more
about
47
gigahertz.
I
think
so.
The
idea
would
be
to
see
if
we
can
compare
the
two
and
see
see
if
we
can
make
47
gigahertz
as
productive
as
as
is
possible.
A
We
should
also
use
I'm
not
going
to.
I
think
michelle
and
others
are
going
to
talk
about
dbps
to
x
a
lot
so
they'll
tell
you
about
the
main
features,
but
there
is
a
mode
called
adaptive
coding
and
modulation
where
we
we
every
few
milliseconds
adjust
the
the
modulation
encoding
scheme
based
on
the
link
performance
that
the
user
receives
on
the
ground.
A
So
the
user
would
send
a
signal
back
to
the
spacecraft
advising
whether
the
signal
was
too
strong
or
too
too
weak,
and
based
on
that,
the
modulation
encoding
scheme
at
the
spacecraft
could
be
changed.
So
we
would
think
that
all
the
users
would
be
do
using
that
with
their
radio.
Of
course,
there
are
many
users
sharing
the
satellite,
so
the
satellite
can't
just
change
its
mod
cod
step
just
because
you
would
like
it
to
because
there's
other
people
that
it
has
to
think
about
as
well.
A
Well,
it's
not
really
thinking
very
much
is
it
we
could
upload
large
files
to
spacecraft
and
use
what
I
call
a
data
cast
mode.
So
imagine
you
use
one
of
one
or
several
of
these
narrowband
channels
to
upload
a
big,
really
cool
file
that
everybody
in
the
in
the
world
might
like
to
see.
If
there
was
such
a
thing,
we
could
store
it
on
boat
on
board
and
then
download
it
via
that
wideband
channel
and,
of
course
it
could
be
downloaded
at
what
looks
like
800
or
900
kilobits
per
second.
A
In
this
example,
we've
shown
here,
we
could
also
arrange
the
configuration
of
the
spacecraft
to
support
different
modes
where
you
you
have
24,
gigs
up
and
10.5
down,
which
would
be
the
normal
standard
mode.
You
might
say,
but
then
these
other
modes
could
be
possible
and
that
would
include
a
47
47
up
and
down
where
you
use
some
kind
of
time
division
multiplexing.
A
So
here's
a
challenge
for
you,
this
here's,
a
50,
kilometer
link.
What
we
can
see
from
the
itu
rain
model
is
that
the
path
loss?
Well,
you
don't
need
the
rain
model.
This
is
just
one
over
r
squared
the
path
loss
on
a
50
kilometer
length
would
be
about
160
db
at
47,
gigahertz
and
since
there'd
be
a
lot
of
47
gigahertz
radios
around.
A
Now
that
we
were
talking
to
satellites,
they
might
decide
to
talk
across
town
or
across
county
to
their
to
their
friends,
and
this
is
kind
of
what
this
looks
like.
So
the
the
challenge
for
you
guys
would
be
what
is
the
excess
path
loss
across
this
50
kilometer
link
and
what
size
is
this
the
right
size
equipment
to
do
the
job?
I
suspect
it's
more
than
you
need.
You
could
probably
use
a
lot
smaller
antennas
for
such
a
short
link.