VX-7R O
PERATING
M
ANUAL
100
A
PPENDIX
U
SING
YOUR
VX-7R
FOR
L
OW
-E
ARTH
-O
RBIT
FM S
ATELLITE
C
OMMUNICATION
Several Low-Earth-Orbit satellites, such as UO-14 and AO-27, utilize a single-channel FM
“repeater in the sky” transponder, affording low-power stations the opportunity to make
contacts with other stations thousands of miles away. Communication generally is most
easily possible when using a hand-held transceiver (like the
VX-7R
) in conjunction with a
small beam antenna, so as to improve your uplink signal.
Because the satellites are moving rapidly, you must compensate for Doppler Shift on the
satellite signal. This is best accomplished by utilizing five “split” memory channels, cover-
ing sufficient frequency combinations, on the 144 and 430 MHz bands, to allow complete
frequency coverage with quick selection.
Example: Set up for operation on UO-14’s transponder:
Set up your
VX-7R
with five “odd split”
memories as shown at the right, to com-
pensate for Doppler Shift:
At the start of the pass, set to Channel 1.
As the pass progresses, rotate the channel
selector to choose the channel with the best
downlink signal. The satellite moves fast
(the optimum channel will change every three minutes!) so be alert. Keep calls short, as
much of your continent will be calling on a single FM channel!
More information on UO-14 and other satellites may be found on the Web site of the
Amateur Satellite Corporation:
www.amsat.org
(or on other satellite-based Web sites).
AOS = Acquisition of Signal (Beginning of Pass)
LOS = Loss of Signal (End of Pass)
CH #
1
2
3
4
5
R
X
F
REQ
435.080 MHz
435.075 MHz
435.070 MHz
435.065 MHz
435.060 MHz
T
X
F
REQ
145.9700 MHz
145.9725 MHz
145.9750 MHz
145.9775 MHz
145.9800 MHz
N
OTES
AOS
Mid Pass
LOS
