PALSTAR
Palstar products are designed by
Hams for Hams carrying on the
Palstar tradition for high-quality
products designed and
manufactured in Ohio, USA.
BT1500A 1500 Watt
Balanced Antenna Tuner
BT1500A Balanced Antenna Tuner
Technical Manual
l 1500 Watts PEP
l 160m to 15m
l Custom variable capacitors and inductor
l Dual movement cross needle meter
l 13 1/4” x 6 1/2” x 16 7/8”
9676 N. Looney Rd,
Piqua, OH 45356 USA
(937) 773-6255
(800) 773-7931
(937) 773-8003 (Fax)
www.palstar.com
PALSTAR
Designed and Manufactured in the USA
Copyright 2014 Palstar, Inc.
BT1500A SPECIFICATIONS
l METERING:
NOTES:
Dual movement cross-needle power
and frequency compensated coupler
l I N P U T & A N T E N N A T U N I N G : V a r i a b l e c a p a c i t o r 9 6 0 p F & 6 5 p F,
4.5 kV Peak , 6:1 Ver nier Dr ive
l INDUCTANCE:
1 5 μ H r o l l e r i n d u c t o r, 1 2 g a . w i r e w o u n d o n
steatite ceramic core, silver plated bar and
wheel
l POWER R ANGE SWITCH: 2 position 300 W / 3000 W
l R E A R PA N E L C O N N E C T O R S :
SO-239: RF Input
END FED WIRE: H igh Voltage N ylon66™
terminal/ground posts for Balanced Line
1 2 V D C I N P U T : 1 4 m m c o n n e c t o r, 2 . 1 m m I D ,
5.5mm OD, center positive, 200 ma
l FREQUENC Y COVER AGE: 1.8 - 29.5 MH z
l POWER MAXIMUM:
1500 W PEP SSB, 1000 W single tone
l IMPEDANCE RANGE: 2500 +/- j2500 160m to 20m
1000 +/- j1000 17m to 10m
l iNPUT BALUN:
1:1 current type balun
l DIMINSIONS:
6.5”H x 13.25“W x 16.875”D (incl. terminals)
l W E I G H T:
17 LBS, 8 Kg
l CHASSIS & COVER:
11 ga., .090 gold Iridite treated Aluminium
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PALSTAR
OPERATING YOUR BT1500A
BT1500A DESCRIPTION
9. When you have tuned your antenna to the best SWR, record
t h e s e t t i n g s o f t h e I N P U T, A N T E N N A , a n d I N D U C TA N C E
controls on the chart above for future reference. When you
retune, use these settings as your starting point.
Notes:
1. A SWR of 1:1 is best, but an SWR as high as 2:1 may be
a c c e p t a b l e . C h e c k y o u r t r a n s m i t t e r / a m p l i fi e r m a n u a l f o r
details.
2. If you cannot get an acceptable SWR, lengthen or shorten
your antenna and/or feedlines and retune.
3. If you get low SWR readings at more than one setting, use
the setting that gives:
- h i g h e s t F O R WA R D p o w e r r e a d i n g
- lowest REFLECTED power reading
- uses the largest capacitance (highest number) on the
INPUT and ANTENNA controls.
4 . A n y t i m e a n e w o r d i ff e r e n t a n t e n n a i s c o n n e c t e d , i t i s
necessary to repeat the turning procedure for each antenna.
5. Once every 4-6 months clean the roller coil with Deoxit
D5 contact cleaner and a clean cotton cloth. Do not remove
the conducting grease on the rod that guides the roller
wheel. Do not transfer any of the conducting grease from
t h e ro d to t h e ro l l e r co i l b o d y, a s t h i s w i l l co n t a m i n a te t h e
windings.
Page 17
The Palstar BT1500A Antenna Tuner is an American-made impedance
matching network.
The BT1500A optimizes the performance of your antenna and
transmitter by providing adjustable impedance matching using
balanced dual tandem roller inductors with a shunt capacitor that can
be switched to the input (transmitter) side or the output (antenna) side.
The BT1500A also measures the power and Voltage Standing Wave
Ratio (VSWR or SWR), which allows you to tune the SWR to the lowest
ratio possible for the selected transmission frequency.
A switch allows the user to choose Average or Peak metering. Also, a
Peak Hold function holds the peak reading for approximately 2
seconds for easier reading.
Front panel controls allow for selection between two ranges of variable
capacitance, and allow the shunt capacitor to be switched between the
input (transmitter) side (low Z, high pass) and the output (antenna) side
(high Z, low pass).
Tuning is achieved with the front panel controls. The Vernier
capacitor dial allows for fine tuning with precision and accuracy,
while the Inductor crank handle provides coarse adjustments.
The range of the power meter (300W/3000W) is selected
by a pusch button switch located on the front panel.
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PALSTAR
INSTALLATION
OPERATING YOUR BT1500A
U N PA C K I N G
Carefully remove the BT1500A from the shipping carton
and inspect it for signs of damage. If any damage is
apparent, notify the transportation carrier or dealer
i m m e d i a t e l y . K E E P T H E PA C K I N G C A R T O N f o r m o v i n g ,
storing, or reshipping the tuner to us for repair if
required.
5. Set POWER RANGE switch to 300 W (button out).
6. Key your transmitter and adjust the power level for a
r e a d i n g o f 5 0 - 1 0 0 w a t t s o n t h e F O R WA R D s c a l e . A d j u s t t h e
I N P U T, O U P U T, a n d I N D U C T O R c o n t r o l s f o r a m i n i m u m
R E F L E C T E D r e a d i n g w h i l e m a i n t a i n i n g a F O R WA R D r e a d i n g
of 50-100 watts using your transmitter power control. Use
the supplied chart of approximate tuning control locations
f o r t h e d i ff e r e n t b a n d s l o c a t e d a t t h e b a c k o f t h e m a n u a l .
L O C AT I O N
Select a location for the BT1500A that allows the
connectors to be free from any possible contact with
people, pets, or objects during operation and with
u n r e s t r i c t e d a i r fl o w f o r c o o l i n g .
2.1 mm
FEMALE plug
Grey
TRACE ID
Protection
Reverse diode
Red Heat Shrink
cover
+ To 12-13.8v
- Power Supply
7. Read the SWR on the red scale at the point where the two
needles intersect. Repeat TUNING the input and antenna
controls until the lowest SWR reading is obtained.
T h i s p r o c e d u r e t a k e s p a t i e n c e t h e fi r s t t i m e . T h e i n p u t
and antenna controls vary the capacitors and provide
fi n e a d j u s t m e n t s , w h i l e t h e r o l l e r i n d u c t o r c r a n k
provides coarse adjustment.
When approaching the end stops of the roller inductor
( re a d i n g s o f Ze ro o r 2 7 9 ) S LO W D O W N . S l a m m i n g t h e
roller wheel into the mechanical end stops on either
end of the roller inductor will decrease the pressure of
the wheel against the wire wound on the ceramic form.
BT1500A DC POWER CORD
I N S TA L L AT I O N P R O C E D U R E
Connect a coax cable from your transmitter to the RF
INPUT connector on the rear panel. Keep the cable as
s h o r t a s p o s s i b l e . I f y o u u s e a l i n e a r a m p l i fi e r, c o n n e c t
y o u r t r a n s m i t t e r t o t h e l i n e a r a m p l i fi e r i n p u t a n d t h e
l i n e a r a m p l i fi e r o u t p u t t o t h e B T 1 5 0 0 A .
To RESTORE wheel pressure on
the inductor push down on the
flat springs soldered to the
wheel shaft located on each
end of the shaft.
D O N O T U S E M O R E T H A N 1 0 0 0 WAT T S ( s i n g l e t o n e
c o n t i n u o u s ; 1 5 0 0 W P E P S S B ) t h r o u g h t h e t u n e r.
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PALSTAR
OPERATING YOUR BT1500A
REAR PANEL
B E F O R E O P E R AT I N G
1 . To a v o i d p o s s i b l e d a m a g e t o t h e B T 1 5 0 0 A s e t I N P U T,
O U T P U T, I N D U C T O R , a n d P O W E R R A N G E s w i t c h e s a s o u t l i n e d
i n t h e c h a r t b e l o w b e f o r e a p p l y i n g t r a n s m i t t e r p o w e r.
2. Begin tuning with your transmitter/amp feeding the tuner
set at a low output power setting (50-100 Watts max).
BALANCED OUTPUT
Two Nylon High Voltage post connectors for output
to RF balanced transmission lines. Balanced line of
any impedance (300Ω, 450Ω, 600Ω ) can be used.
WA R N I N G : D O N O T O P E R AT E T H E
B T 1 5 0 0 A W I T H T H E C O V E R O F F.
TUNING
1. Select the band and frequency of desired operation.
2. Set TUNE and INDUC TOR controls to the suggested setting
before applying transmitter power (see chart). Actual settings
will vary from antenna to antenna.
3 . S e t y o u r t r a n s m i t t e r / a m p l i fi e r t o 1 0 0 - 1 5 0 w a t t s L O W o u t p u t .
If your transmitter has a TUNE position, select that position.
4 . P r e s e t t h e I N P U T, O U T P U T, a n d I N D U C T O R v a l u e s s h o w n i n
the char t. Select type of antenna feed, BALANCED or COAX.
N O T E : M I N I M U M I N D U C TA N C E i s 2 2 9 ( m a x t u r n s c l o c k w i s e ) .
M A X I M U M I N D U C TA N C E i s 0 ( Z E R O ) o n t h e t u r n s c o u n t e r.
INPUT
BAND
SUGGESTED
ACTUAL
SWITCH SETTING
INDUCTOR
HI-C/LO-C
HI-Z/LO-Z
SUGGESTED
160 M
66
HI-C
HI-Z
156
80 M
35
HI-C
HI-Z
184
40 M
20
HI-C
HI-Z
215
20 M
11
HI-C
HI-Z
231
15 M
35
HI-C
HI-Z
237
12 M
18
HI-C
HI-Z
238
10 M
15
HI-C
HI-Z
240
Page 15
ACTUAL
RF INPUT coaxial
connector for input from
transmitter or amplifier
GROUND post/wing nut
ground connector
Page 4
12 VDC INPUT
(2.1 mm plug,
center pin +)
12 VDC adapter
500 mA to power
the metering ,lamp,
relay, and fan.
PALSTAR
FRONT PANEL DESCRIPTION
1
2
34
INSIDE VIEW
VARIABLE
CAPACITORS
5 6 7 8
COUPLER
ROLLER
INDUCTORS
9
1. TUNE. Dual section variable capacitor (960 & 65pF). Can be switched
from output to input side of network using switch #4.
2. POWER/SWR METER. Dual needle meter displays FORWARD and
REFLECTED power in watts. SWR is measured where the two needles
intersect on the red scale. Metering works only if the unit is provided
with 12VDC at the rear power jack.
3. Hi-Lo PASS. Two position switch selects Low Pass (High Z, capacitor on
input side). The switching is performed with a 40 amp contact relay. This
function only works if the unit is provided with 12VDC at the rear
power jack.
4. Hi-Lo CAPACITOR. Two position switch selects the low value variable
capacitor section of 65pf, or parallels the two sections for a total of
1025pf. The switching is performed with a 40 amp contact relay. This
function only works if the unit is provided with 12 VDC at the power jack.
METERING
ASSEMBLY
PEAK/HOLD
PCB
5. PEAK HOLD. Select to read Peak Hold on the SWR meter. Peak switch
(Button #6 above) must be in PEAK position.
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PALSTAR
METER BOARD ADJUSTMENTS
Reverse
Low
Reverse
High
Forward
Low
Forward
High
6. PEAK Selects between PEAK and AVERAGE power metering display.
7. RANGE. Two-position switch selects the range of FORWARD and
REFLECTED power displayed on the power meter.
When the RANGE button is OUT, the FORWARD meter scale reads 300
watts full scale and the REFLECTED meter reads 60 watts full scale.
Peak
Hold
Peak Peak Power Peak On/Off
Low Range High
When the RANGE button is IN, the FORWARD meter scale reads 3000
watts full scale and the REFLECTED meter reads 600 watts full scale.
8. POWER. A two position button. When in the IN position, turns on meter
illumination and powers the Hi-Lo Pass and Hi-Lo Capacitor switch
functions and the metering functions. The unit must be provided with
12VDC at the rear power jack.
9. INDUCTOR 15 μ H roller inductors mounted in tandem
controled by turns counter.
Page 13
Page 6
PALSTAR
UNDERSTANDING YOUR TUNER
T h e P a l s t a r B T 1 5 0 0 A a n t e n n a t u n e r i s a h i g h l y fl e x i b l e m a t c h i n g
device intended for use with antennas that use balanced or parallel
t r a n s m i s s i o n l i n e s . To o b t a i n t h e b e s t p e r f o r m a n c e f r o m t h e t u n e r,
you should understand how the tuner works and how it relates to
your antenna and feedline.
UNDERSTANDING YOUR TUNER
by the station you are working.
T h e s k e t c h s h o w s t h e g e n e r a l i d e a . Yo u c a n i n s e r t t h e l o o p
manually or with a system of switches. Knife switches work very
well for parallel transmission line,
Basic operation: Examine the schematic diagram of your tuner to
see all of the electronic features. In this discussion, we shall focus
only upon the matching net wor k itself. The basic circuit under
d i s c u s s i o n i s a b a l a n c e d L- n e t wo r k w i t h t h e s h u n t c a p a c i t o r o n t h e
output side.
since they will handle the high voltages that may be present on
parallel transmission lines. As with any run of parallel transmission
line, you must keep the line free and clear of metallic objects. As
well, do not coil the line itself. I nstead, make a single large loop.
A s i n g l e - e n d e d L- n e t wo r k - t h e m o s t c o m m o n v a r i e t y - u s e s a
certain value of inductance (L) and a certain value of capacitance
( C ) t o e ff e c t a m a t c h a t a p a r t i c u l a r f r e q u e n c y f o r a p a r t i c u l a r
antenna feedline impedance and length. For coaxial cable systems,
t h e s i n g l e - e n d e d L- n e t wo r k p ro v i d e s t h e l o we s t l o s s o f a ny
n e t w o r k m a t c h i n g s y s t e m . H o w e v e r, o n e l i m i t a t i o n i s t h a t w i t h t h e
capacitor on the antenna side of the coil, the system is limited to
antenna terminal impedances greater than about 50 Ohms. If we
wish to use the single-ended network with a balanced feedline, we
have to add a balun on the output side of the network. Baluns work
best with very low values of reactance on their output terminals,
a c o n d i t i o n t h a t i s d i ffi c u l t t o o b t a i n w i t h m o s t a n t e n n a s t h a t u s e
parallel feedlines.
T h e b a l a n c e d ve r s i o n o f t h e L- n e t wo r k o ve rc o m e s t h i s l i m i t a t i o n
by providing a true balanced output direc tly from the net work . For
a p a r t i c u l a r a n te n n a , o p e r a t i n g f re q u e n c y, a n d t r a n s m i s s i o n l i n e
impedance and length, the matching circuit requires the same total
circuit inductance and the same output capacitance as the
s i n g l e - e n d e d n e t w o r k . H o w e v e r, t h e b a l a n c e d c i r c u i t d i v i d e s t h e
inductance into two equal series portions, one in each leg of the
network. The shunt capacitor has the same value in both versions
o f t h e L- n e t wo r k .
U n l i k e t h e s i n g l e - e n d e d L- n e t wo r k , t h e l e g s o f t h e b a l a n c e d
L- n e t wo r k a re b o t h a b o ve t h e g ro u n d p o t e n t i a l. H e n c e, b o t h t h e
input and antenna sides of the network are balanced. In order to
accommodate the single-ended transmission line from the
Page 7
The size of the loop depends on the frequency of operation and
how much further along the line you must go to obtain an
impedance value that falls within the tuner limits.
It is possible to calculate favorable line lengths for each band for
any combination of antenna and feedline. The very large variety of
antennas and the many types of feedlines used by amateur
operators place such calculations outside the scope of these notes.
M o s t o p e r a t o r s fi n d i t q u i c k e r t o e x p e r i m e n t w i t h v a r i o u s l i n e
lengths until the uncover the right combinations for each band.
T h e b a l a n c e d L- n e t wo r k , t h e t r a n s m i s s i o n l i n e, a n d t h e a n t e n n a
f o r m a t o t a l s y s t e m t h a t i s v e r y fl e x i b l e . T h e i n i t i a l i n a b i l i t y t o fi n d
a 1:1 SWR match for the system is not a fault of any of the three
major components. Instead, the situation is a normal function of
the dynamics of the antenna feedpoint impedance and its
t r a n s f o r m a t i o n a l o n g t h e t r a n s m i s s i o n l i n e . Yo u m a y a l t e r a n y o f
the three components of the system to arrive at an impedance at
the antenna terminals that the tuner can match. In most cases, but
not all, modifying the transmission line length is the easiest
te c h n i q u e. A l te r n a t i ve l y, yo u m ay a l te r t h e a n te n n a l e n g t h a s we l l.
There are many resources available for learning more about your
antenna and feedline system. The ARRL Antenna Book is a good
place to start. In addition, there are numerous aids to making
calculations of what is occuring in the system.
The more that you know about your antenna and
f e e d l i n e s y s t e m , t h e m o r e e ff e c t i v e y o u w i l l b e
a b l e t o u s e y o u r P a l s t a r B T 1 5 0 0 A a n t e n n a t u n e r.
Page 12
PALSTAR
UNDERSTANDING YOUR TUNER
Yo u r A n t e n n a a n d F e e d l i n e : t h e b a l a n c e d L - n e t w o r k c a n b e u s e d
with any antenna fed with parallel feedline. Parallel feedlines may
range from 300 Ohm T V twin lead, to “windowed” lines in the
400-450 Ohm range, to 600 Ohm (and higher) ladder lines. The
a p p l i c a b l e t y p e s o f a n t e n n a s i n c l u d e fl a t - t o p a n d V e e ’d a l l - b a n d
doublets, horizontally or vertically oriented loops, end-fed wires,
and arrays such as the lazy-H and the 8JK. There are also a number
o f d e s i g n s f o r w i r e Ya g i s a n d q u a d b e a m s t h a t e m p l o y p a r a l l e l
transmission lines.
At a ny gi ve n o p e r a t i n g f re q u e n c y, t h e a n te n n a h a s a ce r t a i n
feedpoint impedance. For most multi-band antennas, the feedpoint
i m p e d a n ce w i l l c h a n g e w i t h t h e o p e r a t i n g f re q u e n c y. O n m o s t
bands, the impedance will be complex, that is, a combination of
r e s i s t a n c e a n d r e a c t a n c e . H o w e v e r, u n l e s s y o u r f e e d l i n e h a p p e n s
to be an exact multiple of a half wavelength (accounting for the
l i n e ’s v e l o c i t y f a c t o r ) o r u n l e s s t h e f e e d p o i n t i m p e d a n c e i s
identical to the characteristic impedance of the feedline, your
antenna tuner will not encounter the antenna feedpoint
impedance.
For any condition where the feedpoint impedance does not exac tly
match the characteristic impedance of the feedline, the impedance
will vary continuously along the feedline, returning to the
feedpoint value at every half wavelength along the line. The
p r e c i s e v a l u e s t h a t y o u w i l l e n c o u n t e r a t s o m e s p e c i fi c p o i n t a l o n g
the line depend upon the characteristic impedance of the line, its
v e l o c i t y f a c t o r, a n d t h e f e e d l i n e i m p e d a n c e i t s e l f . T h e r a n g e o f
variation in both resistance and reactance is a function of the
d e g r e e o f d i ff e r e n c e b e t w e e n t h e f e e d p o i n t i m p e d a n c e a n d t h e
characteristic impedance of the feedline.
Many users of multi-band antennas are surprised to learn that even
very high feedpoint impedances can result in very low impedances
at certain regions along the feedline. An end-fed wire at any
f re q u e n c y, o r a ce n te r - fe d w i re t h a t i s c l o s e to a m u l t i p l e o f a
wavelength long will present a very high impedance. If your
f e e d l i n e i s t h e r i g h t l e n g t h , y o u m a y fi n d t h a t t h e i m p e d a n c e a t
t h e a n te n n a te r m i n a l s i s ve r y l ow. A l te r n a t i ve l y, a t o t h e r l e n g t h s,
you may discover that the reactance at the antenna terminals is
outside the range for which the output capacitor can compensate.
Without careful computation, you may not know which condition
a p p l i e s . Yo u m a y o n l y k n o w t h a t t h e t u n e r s e e m s u n a b l e t o p r o v i d e
1 : 1 S W R f o r t h e l i n e t o t h e t r a n s m i t t e r.
A S i m p l e Wo r k-Aro u n d : Th e re a re m a ny w ays to co r re c t t h e
p r o b l e m o f b e i n g u n a b l e t o e ff e c t a g o o d m a t c h o n o n e o r m o r e
bands of operation when using a feedline into the length from the
tuner of the antenna. Since the losses on the parallel line are very
l ow, a fe w e x t r a fe e t o f t r a n s m i s s i o n l i n e w i l l n o t b e d e te c t a b l e
Page 11
UNDERSTANDING YOUR TUNER
t r a n s m i t t e r, t h e t u n e r p l a c e s a 1 : 1 c h o k e ( c u r r e n t ) b a l u n b e t w e e n
t h e i n p u t s i d e o f t h e n e t w o r k a n d t h e t r a n s m i t t e r c o a x c o n n e c t o r.
The balun converts the unbalanced input from the transmitter to
a balanced condition for the network. As well, it suppresses
currents that might otherwise appear on the braid of the
transmitter cable.
L i m i t a t i o n s : E v e r y a n t e n n a t u n e r, n o m a t t e r w h a t t h e t y p e , h a s
limits to the range of impedances that it will match to the 50 Ohm
i n p u t . T h e b a l a n c e d L- n e t wo r k i s n o e xc e p t i o n . U n d e r s t a n d i n g
t h o s e l i m i t a t i o n s w i l l h e l p y o u t o e ff e c t a m a t c h o n e v e r y b a n d .
The impedance presented to the tuner antenna terminals is usually
expressed as a series combination of resistance and reactance, that
i s, R + / - j Z O h m s. T h e L- n e t wo r k t h a t p l a c e s i t s s h u n t c a p a c i t o r o n
t h e a n t e n n a s i d e i s n o r m a l l y a n u p c o n v e r t e r. T h e l i m i t i n g l o w e r
end impedance is in the vicinity of 60 to 100 Ohms resistive for a
50 Ohm input. The upper limit of impedance that the network will
m a tc h i s a co m p l e x f u n c t i o n o f f re q u e n c y, t h e co m p o n e n t v a l u e s,
and the amount of reactance that is part of the impedance at the
tuner terminals. For most of the HF Amateur bands, the upper
i m p e d a n c e l i m i t o f t h e b a l a n c e d L- n e t wo r k i n t h e Pa l s t a r B T 1 5 0 0 A
tuner is about 2500 +/- j2500 Ohms. This upper limit descends
slowly with rising frequency so that at 30 MHz the upper limit is
about 400 +/- j400 Ohms. The decrease in range results from the
unavoidable minimum capacitance of the output variable
c a p a c i t o r.
The impedance presented to the antenna terminals may be any
value of R and any valye of X. For a given R component, the tuner
w i l l r e q u i r e a c e r t a i n s e t t i n g o f t h e c o i l a n d a l s o t h e c a p a c i t o r. I f
there is reactance at the antenna terminals, then the network
requires a lower value of C if the reactance is capacitive, and a
higher value of C if the reactance is inductive. The network
compensates for the reactance by increasing or reducing the
capacitive reactance required for a purely resisitive load with only
small changes in the required inductance. The amount of
compensation available is a function of the maximum and minimum
values of shunt capacitance and the resulting reactance of this
c o m p o n e n t . W i t h fi n i t e c o m p o n e n t s , t h e r a n g e o f r e a c t a n c e f o r
which the network can compensate is always limited.
As well, every matching network incurs losses within the network,
mostly as a function of the Q of the inductor and the ratio of the
antenna terminal impedance to the input impedance. For the
b a l a n c e d L - n e t w o r k w i t h a s h u n t o u t p u t c a p a c i t o r,
the higher the impedance to be matched, the higher
the losses. The losses will be lower if the reactance
at the antenna terminals is purely resistive.
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BT1500A SCHEMATIC
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