INTRODUCTION
The Heathkit Model
SP-220
Linear Amplifier
is
e
completely self-contained, table top, grounded grid, linear
amplifier.
It
is
designed to operate at the maximum amateur
power limit on
SSB,
CW, and RTTY.
Its
styling matches the
Heath
SB
series of amateur equipment.
The Amplifier
is
designed to
be
used with exciters which
deliver
100
watts
or
more output.
It
can
be
used with less
driving power, but will give a lower output.
A
broad-band, tuned input circuit for each band feeds the
two Eimac
3-5002
triode tubes connected in grounded grid
configuration. The tubes are biased beyond cut-off in the
receive1 mode, and zener-regulated bias controls the idling
current in the transmit mode. The tubes are cooled by a fan.
An ALC circuit develops negative voltage to be fed back to
the exciter to reduce
its
gain when the Amplifier
is
overdriven.
The antenna change-over relay
is
normally actuated by
exciter relay contacts to place the Amplifier in the transmit
mode.
The Amplifier can be operated from either
120
VAC or
240
VAC
50/60
Hz lines and can be easily changed from one to
the other. Operation from a
240
volt line is recommended.
Each side of the line cord
is
equipped with a circuit breaker
to protect againstoverloads.
An important feature of this Amplifier is that
it
can be
tuned up at the one kilowatt limit and can then
be
switched
to operate on
SSB
at
two kilowatts
P.E.P.
input. As the
switching changes both the voltage and current to the final
tubes, the impedance remains the same and no additional
adjustment of tuned circuits
is
required.
The tubes are "instant heating" types, and transmission may
be
started as soon as the Amplifier
is
switched on (after
Here is
a
full legal-limit Amplifier that can take
its
place on
your operating table and give you years of troublefree
pleasure. This Amplifier has a commanding voice.
Read the "Kit Builders Guide" for complete information on
unpacking, parts identification, tools, wiring, soldering, and
step-by-step assernbl y procedures.
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