Hammarlund FM50A - Additional Service Notes

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ADDITIONAL SERVICE NOTES

It

has

been

found

advisable

to tune

L106

and

L107 off the

"center-frequency"

resonance

peak

for

greater

immunity to

ignition

noise

as

well

as

improved

weak-signal

bandpass.

L106

and L107

should

be

peaked

to an inj

ected

frequency

of

10.7075 mc.

(all

other

adjustments

should

be made in the

IF

frequency

of

10.70 mc.). In

some

instances

greater

immunity to

ignition

noise

may be

achieved

by

further

adjustment

of

L 106 and L 107 for maximum

suppression

of

imphlse

noise

in the

presence

of

a weak on-frequency

signal.

L106

and

L107

should

not

be

detuned

so

far

that

the

second

limiter

grid

current

(in the

absence

of

a

signal)

drops below

saturation.

All

units

shipped

on

and

after

September 11, 1961

are

aligned

with L106 and L107

resonated

to

10.7075 mc.

FREQUENCY NETTING

Frequency

Netting

and

periodic

frequency

checks

of

narrow band equipment

is

extremely important

especially

during

the

early

life

of

the

equipment

when

crystals

are

aging

at

their

fastest

rate.

It

is

recom-

mended

that

all

units

be

rechecked

for frequency

tolerance

(and

netted

to the

system

in which they will be

used)

prior to

placing

same in

service.

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