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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

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