<s>
However	O
,	O
very	O
high	O
antennas	O
with	O
high	O
gain	O
have	O
shown	O
33	B-Algorithm
centimeters	I-Algorithm
can	O
provide	O
good	O
long-range	O
communications	O
almost	O
equal	O
to	O
systems	O
on	O
lower	O
frequencies	O
such	O
as	O
the	O
70	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
.	O
</s>
<s>
The	O
band	O
is	O
also	O
used	O
by	O
industrial	B-Algorithm
,	I-Algorithm
scientific	I-Algorithm
,	I-Algorithm
and	I-Algorithm
medical	I-Algorithm
(	O
ISM	B-Algorithm
)	O
equipment	O
,	O
as	O
well	O
as	O
low-powered	O
unlicensed	O
devices	O
.	O
</s>
<s>
Amateur	O
stations	O
must	O
accept	O
harmful	O
interference	O
caused	O
by	O
ISM	B-Algorithm
users	O
but	O
may	O
receive	O
protection	O
from	O
unlicensed	O
devices	O
.	O
</s>
<s>
The	O
900MHz	B-Algorithm
frequency	O
is	O
also	O
used	O
as	O
a	O
reference	O
band	O
e.g.	O
</s>
<s>
to	O
express	O
the	O
total	O
power	O
or	O
impact	O
of	O
the	O
electric	O
field	O
"	O
E	O
"	O
-	O
expressed	O
in	O
V/m	O
-	O
or	O
the	O
power	O
density	O
"	O
S	O
"	O
-	O
expressed	O
in	O
W/m2	O
-	O
of	O
the	O
overall	O
cellular	B-Protocol
frequencies	I-Protocol
emission	O
caused	O
by	O
all	O
frequencies	O
s.a.	O
the	O
four	O
bands	O
850	O
/	O
900	O
/	O
1,800	O
/	O
1,900	O
MHz	O
–	O
which	O
many	O
GSM	O
phones	O
support	O
and	O
mobile	O
phone	O
operators	O
use	O
-	O
used	O
by	O
all	O
mobile	O
phone	O
operators	O
at	O
the	O
same	O
time	O
to	O
a	O
certain	O
space	O
where	O
e.g.	O
</s>
<s>
In	O
1985	O
,	O
the	O
Federal	O
Communications	O
Commission	O
allocated	O
the	O
frequency	O
band	O
between	O
902	O
and	O
928MHz	O
to	O
Part	O
18	O
ISM	B-Algorithm
(	O
Industrial	B-Algorithm
,	I-Algorithm
Scientific	I-Algorithm
,	I-Algorithm
and	I-Algorithm
Medical	I-Algorithm
)	O
devices	O
.	O
</s>
<s>
These	O
phones	O
,	O
which	O
are	O
regulated	O
by	O
Part	O
15	O
of	O
the	O
FCC	O
's	O
regulations	O
,	O
have	O
made	O
amateur	O
use	O
of	O
the	O
upper	O
and	O
lower	O
end	O
of	O
the	O
33	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
somewhat	O
tricky	O
due	O
to	O
the	O
number	O
of	O
these	O
phones	O
used	O
by	O
the	O
general	O
population	O
.	O
</s>
<s>
Aironet	O
(	O
now	O
Cisco	O
)	O
ARLAN	B-Device
.	O
</s>
<s>
A	O
now	O
defunct	O
commercial	O
user	O
of	O
900MHz	B-Algorithm
wireless	O
networking	O
was	O
Ricochet	B-Application
.	O
</s>
<s>
They	O
used	O
900MHz	B-Algorithm
for	O
the	O
"	O
last	O
mile	O
"	O
connection	O
to	O
the	O
user	O
in	O
an	O
early	O
wide	O
area	O
mobile	O
wireless	O
network	O
.	O
</s>
<s>
Less	O
than	O
1	O
W	O
.	O
A	O
cognitive	B-Protocol
radio	I-Protocol
system	O
still	O
being	O
sold	O
and	O
in	O
use	O
as	O
of	O
2011	O
.	O
</s>
<s>
Frequency	O
range	O
from	O
902MHz	O
to	O
928MHz	O
as	O
an	O
unlicensed	O
Industrial	O
Scientific	O
and	O
Medical	O
(	O
ISM	B-Algorithm
)	O
frequency	O
band	O
for	O
North	O
America	O
.	O
</s>
<s>
MotoTalk	O
or	O
with	O
Nextel	O
,	O
DirectTalk	O
,	O
uses	O
the	O
900MHz	B-Algorithm
Part	O
15	O
band	O
.	O
</s>
<s>
It	O
uses	O
FHSS	B-Protocol
and	O
employs	O
10	O
"	O
channels	O
"	O
and	O
15	O
"	O
privacy	O
codes	O
"	O
.	O
</s>
<s>
Motorola	O
makes	O
a	O
line	O
of	O
walkie-talkies	O
(	O
the	O
DTR	O
family	O
)	O
which	O
are	O
FHSS	B-Protocol
digital	O
units	O
.	O
</s>
<s>
Trisquare	O
makes	O
a	O
line	O
of	O
walkie-talkies	O
(	O
the	O
eXtreme	O
Radio	O
Service	O
family	O
)	O
that	O
are	O
also	O
license	O
free	O
FHSS	B-Protocol
units	O
,	O
operating	O
in	O
the	O
900MHz	B-Algorithm
band	O
.	O
</s>
<s>
Today	O
,	O
the	O
33	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
is	O
rapidly	O
becoming	O
popular	O
with	O
many	O
UHF	O
enthusiasts	O
.	O
</s>
<s>
Amateur	O
television	O
is	O
a	O
popular	O
activity	O
on	O
the	O
33	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
,	O
and	O
some	O
manufacturers	O
produced	O
ATV	O
equipment	O
for	O
this	O
band	O
.	O
</s>
<s>
Amateurs	O
who	O
are	O
involved	O
in	O
contesting	O
use	O
home-made	O
or	O
commercially	O
available	O
transverters	O
to	O
operate	O
CW	O
and	O
SSB	B-Device
on	O
the	O
lower	O
end	O
of	O
the	O
band	O
,	O
either	O
just	O
above	O
903MHz	O
or	O
just	O
above	O
902MHz	O
.	O
</s>
<s>
SSB/CW	O
operations	O
usually	O
use	O
horizontal	O
polarization	O
for	O
most	O
contacts	O
.	O
</s>
<s>
Any	O
mode	O
(	O
FM	B-Application
,	O
SSB	B-Device
,	O
CW	O
)	O
can	O
be	O
used	O
.	O
</s>
<s>
Contact	O
scoring	O
is	O
higher	O
for	O
33cm	B-Algorithm
than	O
the	O
lower	O
bands	O
(	O
6m	O
through	O
70cm	B-Algorithm
)	O
.	O
</s>
<s>
Until	O
recently	O
,	O
no	O
amateur	O
radio	O
equipment	O
manufacturer	O
has	O
ever	O
made	O
an	O
FM	B-Application
repeater	O
for	O
the	O
33	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
.	O
</s>
<s>
Amateurs	O
who	O
wish	O
to	O
build	O
a	O
repeater	O
and	O
those	O
who	O
wish	O
to	O
use	O
that	O
repeater	O
must	O
do	O
so	O
using	O
modified	O
commercial	O
equipment	O
designed	O
for	O
use	O
in	O
the	O
mid-800MHz	O
and	O
mid-900MHz	O
range	O
.	O
</s>
<s>
In	O
2012	O
,	O
the	O
first	O
two-way	O
900MHz	B-Algorithm
radio	O
made	O
specifically	O
for	O
the	O
Amateur	O
Service	O
was	O
introduced	O
by	O
Alinco	O
.	O
</s>
<s>
The	O
DJ-G29T	O
is	O
a	O
dual	O
band	O
portable	O
radio	O
operating	O
on	O
the	O
222	O
MHz	O
and	O
900MHz	B-Algorithm
bands	O
and	O
is	O
fully	O
programmable	O
.	O
</s>
<s>
The	O
ARRL	O
(	O
American	O
Radio	O
Relay	O
League	O
)	O
has	O
specified	O
that	O
repeaters	O
on	O
the	O
33	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
use	O
a	O
split	O
of	O
-12MHz	O
with	O
inputs	O
between	O
906	O
and	O
909MHz	O
and	O
outputs	O
between	O
918	O
and	O
921MHz	O
.	O
</s>
<s>
However	O
,	O
the	O
majority	O
of	O
amateur	O
33	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
amateur	O
repeaters	O
use	O
a	O
split	O
of	O
-25MHz	O
with	O
inputs	O
between	O
902	O
and	O
903MHz	O
and	O
outputs	O
between	O
927	O
and	O
928MHz	O
.	O
</s>
<s>
The	O
primary	O
reason	O
being	O
that	O
most	O
amateur	O
repeaters	O
in	O
this	O
band	O
are	O
built	O
from	O
commercial	O
equipment	O
that	O
has	O
been	O
modified	O
to	O
transmit	O
and	O
receive	O
in	O
the	O
amateur	O
33	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
and	O
modification	O
complexity	O
increases	O
rapidly	O
as	O
target	O
frequencies	O
are	O
moved	O
further	O
from	O
the	O
original	O
design	O
frequencies	O
.	O
</s>
<s>
With	O
the	O
explosion	O
in	O
popularity	O
of	O
Nextel	O
phones	O
with	O
a	O
push	O
to	O
talk	O
feature	O
,	O
the	O
marketplace	O
has	O
seen	O
a	O
flood	O
of	O
newer	O
800	O
and	O
900MHz	B-Algorithm
commercial	O
mobile	O
radios	O
that	O
are	O
designed	O
to	O
the	O
following	O
specifications	O
:	O
</s>
<s>
900MHz	B-Algorithm
Radios	O
:	O
</s>
<s>
In	O
addition	O
,	O
the	O
transmitters	O
on	O
many	O
of	O
the	O
aforementioned	O
900MHz	B-Algorithm
radios	O
can	O
be	O
easily	O
modified	O
to	O
transmit	O
lower	O
than	O
935MHz	O
,	O
to	O
about	O
926MHz	O
with	O
acceptable	O
power	O
output	O
.	O
</s>
<s>
With	O
this	O
in	O
mind	O
,	O
many	O
amateurs	O
have	O
opted	O
to	O
set	O
up	O
repeaters	O
with	O
-25MHz	O
splits	O
using	O
modified	O
800MHz	O
radios	O
as	O
receivers	O
and	O
modified	O
900MHz	B-Algorithm
radios	O
as	O
transmitters	O
.	O
</s>
<s>
A	O
number	O
of	O
resources	O
are	O
available	O
for	O
amateurs	O
to	O
build	O
repeaters	O
that	O
can	O
be	O
used	O
on	O
the	O
33cm	B-Algorithm
band	O
.	O
</s>
<s>
Resources	O
are	O
also	O
available	O
via	O
several	O
e-mail	O
discussion	O
groups	O
(	O
such	O
as	O
the	O
Yahoo	O
Groups	O
:	O
"	O
AR902MHz	O
"	O
and	O
"	O
900mhz	B-Algorithm
"	O
)	O
where	O
information	O
regarding	O
conversion	O
of	O
other	O
brands	O
commonly	O
used	O
(	O
such	O
as	O
Kenwood	O
,	O
EF	O
Johnson	O
,	O
and	O
GE/Ericsson	B-Algorithm
)	O
can	O
be	O
found/discussed	O
.	O
</s>
<s>
The	O
advent	O
of	O
issues	O
involving	O
interference	O
to	O
the	O
PAVE	O
PAWS	O
RADAR	O
systems	O
located	O
on	O
the	O
East	O
and	O
West	O
coasts	O
of	O
the	O
United	O
States	O
has	O
pushed	O
many	O
amateur	O
repeater	O
operators	O
to	O
vacate	O
the	O
70cm	B-Algorithm
band	I-Algorithm
in	O
favor	O
of	O
33cm	B-Algorithm
,	O
and	O
proliferation	O
of	O
33cm	B-Algorithm
repeaters	O
has	O
understandably	O
increased	O
exponentially	O
in	O
the	O
past	O
few	O
years	O
.	O
</s>
<s>
Amateurs	O
who	O
use	O
local	O
repeaters	O
on	O
the	O
33	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
use	O
commercial	O
handheld	O
or	O
mobile	O
900MHz	B-Algorithm
radios	O
.	O
</s>
<s>
However	O
,	O
since	O
almost	O
all	O
FM	B-Application
radio	O
equipment	O
used	O
on	O
the	O
33cm	B-Algorithm
band	O
amateur	O
band	O
was	O
previously	O
designed	O
for	O
and	O
internally	O
programmed	O
for	O
frequencies	O
outside	O
the	O
33cm	B-Algorithm
band	O
edges	O
,	O
reprogramming	O
is	O
always	O
necessary	O
to	O
get	O
them	O
working	O
properly	O
between	O
902-928MHz	O
after	O
any	O
physical	O
modifications	O
have	O
been	O
made	O
.	O
</s>
<s>
Many	O
amateurs	O
have	O
found	O
the	O
33	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
to	O
be	O
ideal	O
for	O
linking	O
repeaters	O
together	O
.	O
</s>
<s>
Some	O
of	O
the	O
biggest	O
linked	O
repeater	O
systems	O
in	O
the	O
United	O
States	O
use	O
the	O
33	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
as	O
their	O
link	O
backbone	O
.	O
</s>
<s>
Signal	O
propagation	O
on	O
the	O
33	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
is	O
very	O
dependent	O
on	O
the	O
transmitting	O
and	O
receiving	O
antenna	O
's	O
line	O
of	O
sight	O
.	O
</s>
<s>
Assuming	O
that	O
the	O
transmitting	O
antenna	O
's	O
wavelength	O
,	O
height	O
above	O
average	O
terrain	O
,	O
and	O
effective	O
radiated	O
power	O
is	O
equal	O
,	O
a	O
transmitted	O
signal	O
on	O
33	B-Algorithm
centimeters	I-Algorithm
will	O
,	O
generally	O
speaking	O
,	O
usually	O
travel	O
about	O
3/4	O
of	O
the	O
distance	O
that	O
the	O
same	O
signal	O
would	O
if	O
transmitted	O
on	O
the	O
70	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
.	O
</s>
<s>
The	O
33	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
offers	O
excellent	O
building	O
penetration	O
characteristics	O
since	O
the	O
wavelength	O
is	O
relatively	O
small	O
and	O
can	O
fit	O
through	O
windows	O
more	O
easily	O
than	O
signals	O
lower	O
in	O
frequency	O
.	O
</s>
<s>
In	O
many	O
areas	O
,	O
the	O
33	B-Algorithm
centimeter	I-Algorithm
band	I-Algorithm
also	O
has	O
a	O
very	O
low	O
noise	O
floor	O
as	O
compared	O
to	O
bands	O
lower	O
in	O
frequency	O
.	O
</s>
