DID TEURS

Ace RIC, lnc.. of Higginsvill
e, Missouri, and Royal
Electronics of Denver, Colorado,
al so make rad io kits
for the six-me te r band.
While al l three fi rms offer
so me flexibil ity in the
choice of styles in components,
Ace seemed to have
the widest variety of gear
at lower prices than the
others.
Since mo st RIC rigs operate
o n the same basic principle,
the choice of gear
comes down to the specific
use to which the rig will be
put. For sma ll three-footwingspan
models flown in
small spaces suc h as school
ya rds. the sma llest and
lightest rig is best. For
quarter-sc al e monsters
weighing twenty-five
pounds and spa nning nine
or ten feet, the size and
weight of the rig don't mean
a th ing. It takes very powerful
se rvos powered by large
capacity batteries to move
the ailerons or elevator on
these biggies.
The rad io in the photos is
the seven-cha nnel kit from
Ace RIC , with t he tran smitter
hou sed in a Roya l Eleetronics
case. In operation,
the rig controls the plane
like this: The pilot's th umbs
rest on the two co ntro l
stic ks on the transmitter.
Each stick moves both forward
and back as well as
from side to side. The right
stick controls the ailero ns
(left/right) and the elevator
(forward/back). The left
stick co ntro ls the rudder
(l eft/ri ght) and the motor
speed (forward/back ). The
remaining co ntrols are operated
from switches and
levers on the front and top
of t he case-bo mb-dro p,
la nding-gea r retract, and
wing flaps .
Each stick moves a potentiometer
whi ch varies
the width of a d igital pulse
that becomes part of a
pul se train. The pulse train
has a clock pulse and seven
data pulses, o ne for each
contro l. The transmit carrier
is turned on and off by
the pul se width (A1 emissio
n) set by the pulse train.
In t he aircraft, demodulated
pul ses come from the receiver,
whic h is of standard
supe rhe t design, to th e
decoder board. Here, the
clock pulse enables the circuitry
to ro ute the first
pul se after the clock to the
elevator. the next pul se to
the ailerons, and so on, un til
all seven data pul ses are
distributed to the proper
se rvos .
A se rvo is an e lectro n­
ic a lly-cont rolled electric
motor. It moves an arm that
is mechanically co nnected
to whatever co ntro l on the
plane yo u wish to control.
When the data pul se enters
the servo, it is compared to
a n o n-board pulse-generator
output which is co n­
trolled by a pot, physically
positioned by the servo output
arm. The on-board
pulse is determined by
where the arm is currently,
while the data pulse from
the ground indicates where
the pilot wants the arm to
be positioned. A difference
between these two pulses
produces an error, which
causes the servo motor to
rotate in the proper direction
to move the arm/pot
co mbination to red uce t he
e rror. At zero error, t he
motor sto ps a nd t he servo
idles, waiting for a new positio
n indication to be sent
up from the ground via the
pulse train. While the transmission
method is digital
pul se, the net effect on the
plane is smoot h control,
since the pulse-recurrence
frequency is high enough to
preclude stepping of the
co ntro ls.
In actual use, all th is
highbrow theory is not important
to the pilot and his
plane. As the pilot thinks
" let's do an axial right roll ,"
his thumb moves the transmitter's
right stick to the
right, and as the plane halfrolls
to inverted, he pushes
the stick forward for down
e levato r, holding the nose
up as the seco nd half of the
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Photo B. Th e system buttoned up and ready to install in the
aircra ft. A 6PD T switch (not shown] turns the airborne unit
on and o ff. The receiver/decoder case is covered with thin
foam rubber for protection. Th e servo at lo wer center is one
o f fo ur in the basic system.
Photo C. The rad io room o f a t yp ical powered aircraft. Re-­
ceiver/decoder and battery are both wrapped in one-inch
foam to dampen vibration from the engine. The three servos
control rudder. elevator. and motor speed.
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73 Magazine · April, 1981 57