Page 1
CQ
Reviews:
The
SB-200
Heathkit
Linear
Amplifier
BY
WILFRED
M. S
CHERE
R,.
W2
AEF
T HE
been around for qui te a few years; never-
theless many requests are st
for inform ation on this piece
In
CQ
jo
the Modet HA-14 "KW K
version h
at this time discuss the S
has nev
b (mainly due to the fact that its for
He
view
ad
athkit
of
er
reviewed this table-top kilowatt
already been covere
thi
S8
s situation and inasmuch as
-2
00
Line
8-200
ar
ill
being received
of
omp
.
Amplifi
gea
act" mobile
d')
r.
erunner
. we shall
er
has
2:
I.
nished with a vari able loading
built-in refl
up to 3:1.
,
I,
grid a
pair of
This is realized with a
ectometer
Details
Referring to the sc hema tic diagram at
the
amplifier is
ff
air and is operated in Class 8 using a
572-8
Or
prov
an
T-16
essentially grou nde d-
ides s.w.r. readings
0-L
Pi·
network f
cont
graphite-anode
rol. A
ur
fi
-
g.
This model is rated at 1200 watts p.e.p.
input on s.s.b. and 1000 watts on c.w. which
is available with 100 w
fr
that obtained
an
tr
100 transceivers
power class. This does not
with lower- or higher-p
will see later.
smitt
The
er
S8
. the Heath
-20 0 is a completely self-cont ained
om
or
other exciters in the same
the
S8
att
He
ow
s r.f. drive such as
ath
-1
00I 1
pr
er drivers as
S8
01
eclude its use
-400140 I
and
HW-
we
triod es c
R.f. drive is applied to the tube cathodes
(fi
laments)
works (pi
Use
effici
passive input.
th
ground and prevents the r
from being bypassed to ground th
at
of
enc
maintain s the tube filaments above r.i.
onn
such tuned circuits here ensures better
y with less distortion
ected in parallel.
thro
or
ugh individual m
L types) tuned for eac h band.
RF
C, is a bifilar-wound
at
than
.f-drive
ching net-
with a
choke
po
wer
rou
gh the
unit with a bu ilt-in p
on
ti
quite well
13
attrac tive styling to match the Heath
series of gear and thus makes a neat-looking
j
ob
weighs 35 Ibs.
Full
amateu
fro m 120
co
'Ml
" (H.W
requiring relatively little desk space.
co
verage is
r bands using bandswitc hed inp ut and
/240
mpacted in a 6
.O
.) wrap-arou nd cabinet with
ob
ower
v.a.c., 50
tained on the 3.5-30
supply f
/60
%"
c.p
X 14
or
opera-
.s.
It
Y8"
S8
mc
is
X
It
-
ament-suppl
fil
tr
ansformer.
Th
duct ors,
alone f
added
appropriate ly tapped.
in only for
The
type .
e Pi-netw ork is made
L, and L,. L, is tapped and is used
or
for
ret1e
Th
the 10-
the
80
e panel meter
-meter band operation.
ctometer is an in-line trough-line
y
windi
and
other
ngs
IS-me
b
an
ds for which it is
C. and Coare swi
can
of
up
ter
be switched to
the
using two in-
bands.
powe
L,
tc
r
is
hed
output circuits. The input impedance is
n
om
tuned-input circuit s that need no tuning ad-
justment during o
ohm impedan
*Technical Director,
'CQ Reviews: The Heath
pact" Linear Amplifier,
inally 52 ohms with broa d-b
pe
ration.
Th
e output is dcsigned to w
ce
s that present an s.w.
CQ.
kit
HA-14 "KW Kom-
CQ.
ork
February
and
into
r.
pre-
50
/7
within
1966,
2-
ad
re
there is a sensitivity control) or the reflected
power for which
terms of s.w
be switched to read
0-1000 rna plate
at
pl
The
the relative forward power (fo r whic h
e
the
.r,up
po
tential.
a.l.c. setup is a
to
current
A
meter is
3:1. T
0-100
.L
.e
.
departure
ca
librated in
he
or
met
rna grid-eurre nt,
1500-3000 v.
er
also
from the
ca
n
page 52.
62
• CO •
June,
1969
usual in that
See
its
page
operation is based on an r.t,
110 for
New
Reader Service
•
Page 2
........
r---
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i
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I
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t
Rl,
"!"
28~"
,
,
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I
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,
,
J
--
'----,
- - - - - - - - - - - - - - - -
PC'
c-<
l--
"
--
"
--
-------
C,
~
['
C
.
,.
-----
--
- - - - - -
L ,
--
; '5
..L1OO
C.
>00
---
L,
j--
...L..
2.
-
120
Fig. I
bondswitch
w.
-Sc
hematic
C,
R,
"
.02
alters
for
L
3
the
,
C7and
.02
58
·200
C8to form
02
R.F.
C.I
.02
amplifi
impedance
er
4.7
.0
2 .
~
02
4
L .02 .02
- T
+1
0 •.
(power-supply
-matching
M;
."
and
Pi
m
or
et
ering circuits not shown). The
l input ne tworks for the
va
rious
voltage.
devel
li
fi
er
As
arc
op
star
s
n
ot
ra
ther
ed during
ts to ove r
how
n at the schematic. the tube gri
th
an
on
modulatio
load
heavily bypassed
an
or
C" and some r.f. voltage
grids.
C:I
and C
..
co
mprise a voltage divid
bands.
Other
a.j, voltage that is
n
dr
aw grid current.
to
thus
when
gro
und (by C,-
ap
pea
an
a
rs at
mp
the
det
-
ds
er
ails
are
state
The
in the text.
or
c.w. drive.
T
r.f. circuits
ra
n
sf
er Circuits
arc
switched with a
antenna-changeover relay which is
by the v.o.x. relay in the exciter. O
as follows: During receive. a bias
d.p
opera
pera
of
.d.t,
ted
tion is
- 120
across
voltage is derived a
result ing d.c, voltage
bias f
tr
oll
ed
D l is rev
th
e grid
of
V,
nd
pr
or
re
ducing the gain
stag e in the exciter.
er
se-bias
ed
from which a
rectified by
ovides the
int o n
by an-a.l.c. threshold pot
applied to its ca
supply
to
D ,'sanode exceeds I0 volts.
bleeder. When the r.f. voltage applied
thode
fro
en
m a
of
tial
tap
samp
D,.
auto
the a.l
.c-con
on-condu
of
the
+ 10 volts
on
the
diode
le
The
ma
tic
-
cti
on
plate-
co
n-
volts is applied to
relay coil.
eliminating
of
has h within the
The
the
bias
the
cuts
tube grids
olf
possibility
tube
that might he
in the receiver.
Du
ring this time the relay is not energize
because the exciter-relay
closed,
through
the
an
nor
the
do
relay coil.
tenna is
the
tube
Under
connected,
the
of
plate
the
contacts
grids
dr
this
through
through
current.
generation
heard
are
aw
current
condition.
the
no
rmal-
the
d,
n
ot
du
ct
s and rectifies
the
sary d.e. voltage for
The
ation at the
grids rea
occurs
Th
the c
tion is
f
ore
thresh
old
has be
instant
ch
es the poi nt just below
when the
e
advan
onv
enti
not
tage of this
on
d
ependent
tu
besare
al system. is
it takes hold. thus allow ing it to be
r.f. to supply
the
a.l.c,
en
set f
or
the
neces-
a.l.e. o
pe
r-
the r.f. voltage at the tube
tha
t which
overdrive n.
arra
on so
me
th
nge
at
men
t,
a.l.c. o
over
pe
ove rdrive be-
ra
-
ly-clos
minal
the
antenna-co nnector
relay
ed
of
tha
relay
the
I
wou
exc
co
ntac ts, to the
iter if it is a tr
of
ld
normally
receiver-transmitter setu p.
to be received .
On transmit, the
v
.o
.x. relay ground
lifier-relay
relay fr
om
co
il
throu
the - 120-voll bias source. The
contacts
the
top e
gh R,.energizing the
a se
be used with a
This
nd
ante
an
sceiver; or to
pa
ra
nna ter-
te tr
ansfer
allows signals
on
the
of
exciter
th
e amp-
effective pri
t
op
ping or
or
to
overdrive
Since the a.l.c. is n
c
omp
voltage
See
on
page
ent
ca
110
du
n be
for
ri
th
ng
pr
oduce
New
e
occur
.
ot
m
Reader
rence of
depende
od
ulation. the a.l.c.
d ev
en
nt
on an a.I.
with stea
Service
any
flat-
dy
-
n
ormall
y ope n
contacts
the exciter-setup
the linear
linear's
At
th
and
out
e sa
transferring
put.
me
output
time,
June
,
1969
then close,
to
th
e resistance
the
the
• CO • 63
r.f.
antenna
connecting
input
to
of
of
the
th
e
Page 3
mf
of
filter
capacita
nce pro vided by six 125
mfd ,
in series. Voltage-equalizing resistors are in-
sta lled across the c
450
v., electrolytic capacitors
ap
acit
or
s.
Th
ey
co
nnecte d
also serve
as a bleede r.
The
windings
l2
0-v
operation.
installed in
power
olt
ope
that
ration. or in series for
An
one
transfor
arc
8-ampere circuit breaker is
leg
co
of
me
r has two
pr
im
ary
nnected in parallel f
24
0-volt
eac
h winding.
or
•
Top
supply components is at upper left with circuit.
view of
the
58.200. Enclosu
re
for powe
r-
Construct
The
top
One
of
encloses the amplifier pro p
for which
manner th
grid-filament
th
at
could
A small
58-200 is asse
mb
which are two shielded
arc
at
eliminates the possibility
short
occur
moto
m
ount
ed h
due
after long usc.
r-driven fan is l
neath the tuhes and
blowing air upwards against the portion of
ion
led
to fila
pr
ovides
on
co
or
a
ch
assis
m
part
er
, the tu
ments.
izont ally in a
men
t sagging
oc
ated be-
coo
ling by
be
of
on
s
a
breakers on
is
at
center fore
below
relay coil and RI form a voltage divider
propor tioned
the ci
R
I.
tube g
the right. The input networks are in the
the tube sockets at the right. A
cover fits over the enclosures.
rc
uit produces a drop of 2 volts across
This appea
ri
ds and thus provides ope
its
gr
right
ound with the bifilar filament
th
at the current drawn throug h
rs
wall.
The amplifier enclosure
as a negative voltage at
ra
ch
perfora
ting bias
oke
ted
so
th
e
each tube envelope opposite the tube plate.
Perf
enclosure
provide an air-flow path for
and warm-air exhaust.
off when the power switch is
circuit arc
loading
th
or
The
an
ations
on
cove
the chassis deck and in the
r and the amplifier cab inet
coo
The
fan
operated .
variable capacitors for the pi-
ce
ra
mic-insulated. The one for
is
a two-gang
the usual t.r.I. receiving type.
job
somewh
l-air i
goes
nt
on
output
at huski
The
plate-
ake
or
er
for
tu
the chang
connected directed to the exciter setup for
normal low-power operation without the
li
heating filame nts.
solid-state rectifiers in the power supply which
the
When
rned off',
near.
The amplifier tubes have instantaneous-
amplifier tuhes.
the pow
th
ere is no bias voltage to ope
eove
r relay, so the antenna remains
er
switch
so
on
along with the use
the
58-200
ra
is
te
of
tuning cap acitor is a wide-s paced high-volt-
age type.
wound with # 10 wire, L:!is wound with # 14
wire
are installed
partment
l
oc
with mic a fixed capacitors .
Th
on
e
a fiberglass form.
tuned
ated. Slug-tuned inductors
The
bifilar fila
L,
on
is a self-sup
circuits for the
on
the rear
which the tube
men
t c
of
ho
porting
cat
the ampli
socke
arc
ke is
hode input
ts also arc
used alo ng
wo
indu
fie
r
ct
co
or
m-
und with
also are instantaneously-performin g devices.
linear-ampli
soo
it
forth between low p
alone
tran
n as
possihle to instantaneously switch back and
Oper ating p
sf
th
or
ormer that has three se
high power from the amplifier.
fi
er operation may be had as
e powerswitch is turned on. making
Pow
ow
er is obtained from a single
ower
er
Supply
from the exciter
co
ndary wind-
# 14 wire
cuts d
qu
wire resist ance for a minimum
ired . raising the Q and holding
age
The
secti
contacts
rent at
Except for the transfo
own
drop
b
ons.Tho
th
on
the
a ferrite
number
co
re, the use
of
turns otherwise re-
.
and
for adequately h
switch
se
e high power levels invo lved.
for the output tank have dua l
emp
loys ceramic-insulated
and
ling the r.f.
rm
er, the power-
fi
la
of
down
me
nt
which
the
vo
lt-
cu
r-
ings; one for 6.3-volt
fil
ament p
ow
er. one for
a - 120-volt bias source and one for a plate
supply
doubler,
e
ac
h leg. is used f
64
• C':l • June,
of
con
2500 volts. A full-wave voltage
sisting of eight silicon diodes in
or
the l
1969
atter
along with
21
supply c
enclosure and are assemb led on a
circui t board. The circuit breakers are
mounted
way that allows
omp
on
See
onenls
one
page
are located in a
wall
them
110
of
for
seco
pr
int
this enclos ure in a
to
be handily reset
Ne
w Reader Serv
nd
ed
ice
-
Page 4
through access holes
of
the
cabine
t is raised.
wh
en
th
e hin g
ed
cover
•
••
,
The reflect
chassis a
is built in a U-shapcd metal
tr
ansmission line
wires held in place
side
th
under the chassis (
lead below the chassis betwee n the band-
switch
of
e fact th
nd
the
and
troug
at
the
on
the
om
et
cr
the insi
co
h is
anten
loading capacitor), mi
is locat ed benea th
de
nduc
by
open
na relay also is expose d
as
of
tor
ny
which, tog
is a long unsh ield
th
e re
tr
ough with
and the pick-up
lon
ar
space rs.
ap
ro n.
et
her with
ght
allow
th
It
th
On
ed
e
e
e
sufficient r.f.
to
c
au
se
TVI
are
boxed in with shielding
sibility
assembly work, thanks to Heath's
ized easy-to-follow ins
ures.
bypassed.
of
No
proble ms were
Upon
TV
to
, ev
Th
I difficulties.
its
beinduced
en
e
co
mpletion, the amplifier func-
job
As
thr
sembly
into
ough
otherwise is
to
encountered
truc
the
minimize
tions
power
ex
and
tem
leads
allead
pretty
the
wi
standard
proced-
well
pos-
th
s
the
-
--
-
-
-
--
Bottom view of the
ard
bo
ef
t. The reflectom
l
for
pow
er
-supp ly
eter
d' h
- --
,....-,~~
-
58·200
pa
trough is
--
. The print
rts it at the lower
at
the center of
•
•
ed
-circuit
•
tioned
ba
t."
the
bu
job;
ilder, 15 ho
properly
A tot al
however, for a less experienced
of
ur
in all respec ts
12 h
s or so may be ne
our
s was r
"right
equired
ed
Operation
Tun
time you d
or worry about
sometimes is the case with high-p
Furtherm
eup
is a simple
on
't
have to
burni
or
e, the range
pr
hurr
ng
oc
up
edur
y the adjustments
of
e
the
the
durin
tub
tun
off
ed.
g which
e grids as
ower
ing con-
the
to
rigs.
do
the rea r
It
th
e exci ter may be slightly off wh
lifier is turned
flect
vary btween
th
er
i
mp
band, and the po
also may be fo
ed impedance) seen by the excit
e is a variatio n in the n
edance of the ampli
apro
n. The blow
cen
on.
I :I and 3: I
because the S.W
rtion
te
und
fie
of the b
er
r.
due
r, d
motor is
that
neor
th
e
tunin
en
.f.
to the fa
om
ep
endin
and
inal inpu t
us
right
g of
the amp-
(or re-
er
ct
g on the
ed.The
will
that
trols is so
are r
critical.
With
t
uned
m
ann
close
its plate
r.f.
first set
ath
er
the
output
er
th
up
. With such drive applied, you then
for
pr
e
for
amp
and
as
op
ort
broad, thus m
li
nea r
maximum outpu t in
lifier's powe r switch and
loading controls
indicated
relative-powe r readings. You're
ion
tu
ed
rned o
th
by
at the
the
ad
justments
ak
ing them non-
ff,
the exciter is
th
e normal
adjus
for
me
maximum
te r whic h is
reflected
various line l
In some cases, slightly re
tunin g may be needed.
With a monitored 100 walls
t
st
ate
120
plate-power input
up amounted
drive
or
imp
240
ed
en
and
volts,
an
ce also will
gths betwee n
to
uc hing
Pe
with a power-line p
to
rformance
measured
of
1150
the
watts
58
-200
th
u
nder
with
ch
an
ge with
e two units.
th
e exciter
of
ot
at fu
an
steady-
ential of
load, the
ll
tune-
r.f',
out-
now read y
transmissions available
58
is a
alo ne, it is best
befo
load presented
the 2:
This
-200
rocke
D
ur
re
I
is especi ally
power
r type).
ing initial
turning
matching
to
go with high-
switch
tune
to
on
to
check
the
the amplifier will fall within
range
important
linear. to m
simp
on
up
of
or
the
the
or
ly
by
off (this switch
with
s.w
for
.r,
linear amplifier.
low-power
flipping the
the
of
ak
e
proper
exciter
the load
sure
load-
the
putof
on
drive.
10% higher,
rating
tra
while
showed the
be within He
a
Unde
pe
775
ll
ba
the
of
zoid display indicate d excellent linearity;
observ
wa
nds. With 100 watts
power
1200 watts p.e.p.
r these conditions
3rd-order
tts.This was esse ntially
input
thus
ations
ath
's specificatio n
of
and
adequa tely fulfilling the
on
a
spectrum
distor
r.f.outpu
inpu
tio n
t.
an
s.s.b. p.e.p.
oscilloscope
products
of
the
anal yzer
-
same
t were
to
30
db
ing as described later. If needed, the s.w.r.,
as
seen by the amplifier, often
dow n by altering
missi
See
on
page
lin e
110
acco
for
the
rdingly.
New
length
Reader
ca
n be
of
Service June,
broug
the t
ran
ht
s-
rela tive to 1000 watts p.e
this was a limitation i
used at the time, The 5th-orde r
- 45 db.
mposed
1969
.p.inp
by
•
ut,
pr
CO
Ac
the exci ter
odu
tua
ct
•
lly,
was
65
Page 5
With 200 walls drive, the amplifie
r
co
uld
On
the other hand , where the exciter de-
be push
walls ou
levels,
fl
ed
tp
att
to 1500 walls input with 1000
ut. With s.s.b. peak pow
op
pin g was not evidenced, excep t
er
at these
for only a slight tendency to round off the
peak
time, a s
order produ ct
level which itself did not
At
of excess ive tube heating or
of
a trapezoid display. At the same
pectrum
to
these high
ana lysis showed the 5th-
rise to
er
-pow
er
ncar
cha
nge significantly.
the
3rd
-order
levels, no evidence
deterior
at
ion was
livers m
a.l.e. w
Su
ch
a.l.e. voltage than that n
the 5B-200. This may be realiz
or
e than 15
ould
be de sirable to limit the drive.
0-200
w
all
s, the use
exciters usu ally will requ ire a
orm
ally
pro
ed
ing the a.l.c, thresh old which can be
co
nnecting the cathode
stead
of
to the
lO
-vo ll t
of
D l to ground, in-
ap
on
th
supply bleeder.
Adjustments both f
or
optimum load ing
of
higher
vided by
by r
do
ed
uc-
ne by
e pow er-
found afte r peri
with s.s.b.
theless, it
opera
rec
tio n exceeds Heat h's specifications
omm
end
or
mu
during
st be kept in mi nd that suc h
ed
od
s
of
on-the-air
opera
tion
rigid benc h tests; neve r-
and
power levels. as well as the
tube ratings. In this respect. Heath's specifi-
cations ca
ll
for a maximu m p.e.p . input
of
1200 walls (with 100 walls drive) using con -
tinuous voice modulation on s.s.b.: while for
c.w, the input is rated at 1000 walls with a
and a.l.c.
serving a trapezoid display on an oscillos
(suc h as the He
opera
tion arc best mad e whil e ob-
co
pe
ath
HO
·I
O
or
5B-6
1O
Mon-
ito r-scopes) by sampling both the d . inp ut
and
test signa l may be used
output
of
the amplifier. Eithe r a two-tone
or
speaking into the
microphone will suffice.
Observations thereby can be mu
ch
more
accurately and easily made than with an r.f.-
envelope display.
Furth
erm
or
e, with the
50
-percent
duty
cycle (key-down time not to
exceed 5 minutes),
With low-
as obtai
nab
transceiver. the amplifier w
500
wall s. Fr
dr
ive levels
of
le from the He
om
the pow
er
45-50 walls, such
ath
ill
levels given h
HW
-1
6 c.w.
put out 450-
er
e-
in, it may be noted that the appare nt gain in
power output decreases with drive levels
(from 10
dr
ive). Thi s is prim
db
with low
arily due to feedthrough
dr
ive to 7
dh
with high
tr
apezoid display
ob
tained as des
you're look ing at only the ampli
mance towards its
elimi
citer
nating possi
pr
ef
ormance as could othe
bl
e
pr
co
op
er adjustment, thus
nfusion with
rw
case with an r.f.-cnvelope display.
One
fin
ply line the amp
with a 240-vo
Th
eref
or
al admo nitio
li
fierdraw
e, f
lt
or
sou
best regulation and overall
n-w
rc
e
ith a I20-volt sup-
s
up
th
e current is 8 a.
to 16 a.; while
fie
r p
ise be
cr
ibed,
erter
th
e ex-
th
-
e
of the r.
ratio to
f-dri
th
e pow
itself at high
ve pow
er
dr
produ c
ive levels than with lower
er
which be
ed
by the ampl
ar
s a smaller
drive.
In order to mainta
ticularl y with high-pow
in
er
goo
d
li
nearity, par-
drive levels, during
tuncup the amplifier must be load ed
yond the maximum -o
past this spot to where the
drop
off.
This
also will be indica t
utput
point; that is.
output
ed
starts to
by a very
to
ifie
be-
r
p
er
formance, a 240-volt source should be
ed
us
is a
As may have alrea
Heath 5B-200 Line
"take
maintaining a goodhard to beat at
ducer
wherev
230·2
it"
is He
40
er
line and n
possible. Also make sure thi s
ot
ar
a 208-volt line.
dy
be
en
Amplifi er c
as well as "dish it ou
quality signal.
th
ath
e kit price
Co
mpany, Benton H
of
$220.
jud
t"
ged, the
an
really
while still
It
is a
Th
e
buy
pro
arbor,
Michi gan 49022. - W1A EF
-
broa
at resonance. The plate current under these
condi tions may be hig
in the manual;however. the tubes will take it.
at least during s.s.b. operation.
or
d
Insu
ot
her
or
ffi
hardly noticeable plate-curre nt dip
cient load
her
in
g can result in
than recommended
fl
attopping
de teriorating effects with high peak
levels, especially on the 40-, 20- and 10-meter
bands wh
peak levels apparently is not quite as favor-
er
e the tank impeda nce for high
able as on
80
and 15. As a matt
was found that with pr
desc
since no
up
levels.
66
ri
bed. usc
fl
att
of
the a.l.c, was not required.
opping
or
other bad effects show
, especia lly at the rec
• CO •
June
, 1
er
op
er loading as just
omm
969
ended power
of
fa
ct
, it
"Actually you'll
See
pa
ge 110 for N
be
aTH
the
..
la,t
."
QSO
ew
R
eader
fram this
Service
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