Palstar BT-1500A User guide

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

 1500 Watts PEP

 160m to 15m

 Custom variable capacitors and inductor

 Dual movement cross needle meter

 13 1/4” x 6 1/2” x 16 7/8”

PALSTAR

BT1500A Balanced Antenna Tuner

Technical Manual

9676 N. Looney Rd,
Piqua, OH 45356 USA

[phone]

[phone]
[phone] (Fax)
www.palstar.com

PALSTAR

Designed and Manufactured in the USA

Copyright 2018 Palstar, Inc.

BT1500A SPECIFICATIONS

 METERING: Dual movement cross-needle power

and frequency compensated coupler

 INPUT & ANTENNA TUNING: Variable capacitor 960pF & 65pF,

4.5 kV Peak, 6:1 Vernier Drive

 INDUCTANCE: 15 μH roller inductor, 12 ga. wire wound on

steatite ceramic core, silver plated bar and

wheel

 POWER RANGE SWITCH: 2 position 300 W / 3000 W

BT1500A DESCRIPTION

The Palstar BT1500A Antenna Tuner is an American-made impedance
matching network.

 REAR PANEL CONNECTORS:

SO-239: RF Input

END FED WIRE: High Voltage Nylon66™

terminal/ground posts for Balanced Line

12 VDC INPUT: 14mm connector, 2.1mm ID,

5.5mm OD, center positive, 200 ma

 FREQUENCY COVERAGE: 1.8 - 29.5 MHz

 POWER MAXIMUM: 1500 W PEP SSB, 1000 W single tone

 IMPEDANCE RANGE: 2500 +/- j2500 160m to 20m

1000 +/- j1000 17m to 10m

 iNPUT BALUN: 1:1 current type balun

 DIMINSIONS: 6/5”H x 13.25“W x 16.875”D (incl. terminals)

 WEIGHT: 17 LBS, 8 Kg

 CHASSIS & COVER: 11 ga., .090 gold Iridite treated Aluminium

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 ne 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.

Page 1

PALSTAR

INSTALLATION

UNPACKING

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

immediately. KEEP THE PACKING CARTON for moving,

storing, or reshipping the tuner to us for repair if

required.

LOCATION

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

unrestricted air ow for cooling.

REAR PANEL

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.

2.1 mm
FEMALE plug

Grey

TRACE ID

Protection

Reverse diode

Red Heat Shrink

cover

+

To 12-13.8v
Power Supply

-

BT1500A DC POWER CORD

INSTALLATION PROCEDURE

Connect a coax cable from your transmitter to the RF

INPUT connector on the rear panel. Keep the cable as

short as possible. If you use a linear amplier, connect

your transmitter to the linear amplier input and the

linear amplier output to the BT1500A.

DO NOT USE MORE THAN 1000 WATTS (single tone

continuous; 1500 W PEP SSB) through the tuner.

Page 2

RF INPUT coaxial

connector for input from
transmitter or amplier

GROUND post/wing nut

ground connector

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 3 4

7 8 9

5

6

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.

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.

When the RANGE button is IN, the FORWARD meter scale reads 3000

watts full scale and the REFLECTED meter reads 600 watts full scale.

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.

5. PEAK HOLD. Select to read Peak Hold on the SWR meter. Peak switch
(Button #6 above) must be in PEAK position.

Page 3

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

controled by turns counter.

μ H roller inductors mounted in tandem

PALSTAR

UNDERSTANDING YOUR TUNER

UNDERSTANDING YOUR TUNER

Your Antenna and Feedline: the balanced L-network can be used
with any antenna fed with parallel feedline. Parallel feedlines may
range from 300 Ohm TV twin lead, to “windowed” lines in the
400-450 Ohm range, to 600 Ohm (and higher) ladder lines. The
applicable types of antennas include at-top and Vee’d all-band
doublets, horizontally or vertically oriented loops, end-fed wires,
and arrays such as the lazy-H and the 8JK. There are also a number
of designs for wire Yagis and quad beams that employ parallel
transmission lines.

At any given operating frequency, the antenna has a certain
feedpoint impedance. For most multi-band antennas, the feedpoint
impedance will change with the operating frequency. On most
bands, the impedance will be complex, that is, a combination of
resistance and reactance. However, unless your feedline happens
to be an exact multiple of a half wavelength (accounting for the
line’s velocity factor) or unless the feedpoint impedance is
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 exactly
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
precise values that you will encounter at some specic point along
the line depend upon the characteristic impedance of the line, its
velocity factor, and the feedline impedance itself. The range of
variation in both resistance and reactance is a function of the
degree of dierence between the feedpoint impedance and the
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
frequency, or a center-fed wire that is close to a multiple of a
wavelength long will present a very high impedance. If your
feedline is the right length, you may nd that the impedance at
the antenna terminals is very low. Alternatively, at other lengths,
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
applies. You may only know that the tuner seems unable to provide
1:1 SWR for the line to the transmitter.

A Simple Work-Around: There are many ways to correct the
problem of being unable to eect a good match on one or more
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
low, a few extra feet of transmission line will not be detectable

transmitter, the tuner places a 1:1 choke (current) balun between
the input side of the network and the transmitter coax connector.

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.

Limitations: Every antenna tuner, no matter what the type, has
limits to the range of impedances that it will match to the 50 Ohm
input. The balanced L-network is no exception. Understanding
those limitations will help you to eect a match on every band.

The impedance presented to the tuner antenna terminals is usually
expressed as a series combination of resistance and reactance, that
is, R +/-jZ Ohms. The L-network that places its shunt capacitor on
the antenna side is normally an up converter. The limiting lower
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
match is a complex function of frequency, the component values,
and the amount of reactance that is part of the impedance at the
tuner terminals. For most of the HF Amateur bands, the upper
impedance limit of the balanced L-network in the Palstar BT1500A
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
capacitor.

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
will require a certain setting of the coil and also the capacitor. If
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
component. With nite components, the range of reactance for
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
balanced L-network with a shunt output capacitor,
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.

Page 4

PALSTAR

BT1500A SCHEMATIC

PALSTAR

15

Page 5

15

COPYRIGHT PALSTAR 2011-2018©

UNDERSTANDING YOUR TUNER

UNDERSTANDING YOUR TUNER

The Palstar BT1500A antenna tuner is a highly exible matching
device intended for use with antennas that use balanced or parallel
transmission lines. To obtain the best performance from the tuner,
you should understand how the tuner works and how it relates to
your antenna and feedline.

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 network itself. The basic circuit under
discussion is a balanced L-network with the shunt capacitor on the
output side.

A single-ended L-network - the most common variety - uses a
certain value of inductance (L) and a certain value of capacitance
(C) to eect a match at a particular frequency for a particular
antenna feedline impedance and length. For coaxial cable systems,
the single-ended L-network provides the lowest loss of any
network matching system. However, one limitation is that with the
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 condition that is dicult to obtain with most antennas that use
parallel feedlines.

The balanced version of the L-network overcomes this limitation
by providing a true balanced output directly from the network. For
a particular antenna, operating frequency, and transmission line
impedance and length, the matching circuit requires the same total
circuit inductance and the same output capacitance as the
single-ended network. However, the balanced circuit divides the
inductance into two equal series portions, one in each leg of the
network. The shunt capacitor has the same value in both versions
of the L-network.

Unlike the single-ended L-network, the legs of the balanced
L-network are both above the ground potential. Hence, both the
input and antenna sides of the network are balanced. In order to
accommodate the single-ended transmission line from the

by the station you are working.

The sketch shows the general idea. You can insert the loop
manually or with a system of switches. Knife switches work very
well for parallel transmission line,

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. Instead, make a single large loop.

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.
Most operators nd it quicker to experiment with various line
lengths until the uncover the right combinations for each band.

The balanced L-network, the transmission line, and the antenna
form a total system that is very exible. The initial inability to nd
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
transformation along the transmission line. You may alter any of
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
technique. Alternatively, you may alter the antenna length as well.

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
feedline system, the more eective you will be
able to use your Palstar BT1500A antenna tuner.

Page 6

PALSTAR

METER BOARD ADJUSTMENTS

INSIDE VIEW

Reverse

Low

Reverse

High

Forward

Low

Forward

High

VARIABLE

CAPACITORS

COUPLER

ROLLER

INDUCTORS

Peak
Hold

Peak Peak

Low

Power
Range

Peak
High

On/O

Page 7

METERING
ASSEMBLY

PEAK/HOLD

PCB

PALSTAR

OPERATING YOUR BT1500A

OPERATING YOUR BT1500A

BEFORE OPERATING

1. To avoid possible damage to the BT1500A set INPUT,

OUTPUT, INDUCTOR, and POWER RANGE switches as outlined

in the chart below before applying transmitter power.

2. Begin tuning with your transmitter/amp feeding the tuner

set at a low output power setting (50-100 Watts max).

WARNING: DO NOT OPERATE THE

BT1500A WITH THE COVER OFF.

TUNING

1. Select the band and frequency of desired operation.

2. Set TUNE and INDUCTOR controls to the suggested setting

before applying transmitter power (see chart). Actual settings

will vary from antenna to antenna.

3. Set your transmitter/amplier to 100-150 watts LOW output.

If your transmitter has a TUNE position, select that position.

4. Preset the INPUT, OUTPUT, and INDUCTOR values shown in

the chart. Select type of antenna feed, BALANCED or COAX.

NOTE:

MAXIMUM INDUCTANCE is 0 (ZERO) on the turns counter.

MINIMUM INDUCTANCE is 229 (max turns clockwise).

5. Set POWER RANGE switch to 300 W (button out).

6. Key your transmitter and adjust the power level for a

reading of 50-100 watts on the FORWARD scale. Adjust the

INPUT, OUPUT, and INDUCTOR controls for a minimum

REFLECTED reading while maintaining a FORWARD reading

of 50-100 watts using your transmitter power control. Use

the supplied chart of approximate tuning control locations

for the dierent bands located at the back of the manual.

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.

This procedure takes patience the rst time. The input
and antenna controls vary the capacitors and provide
ne adjustments, while the roller inductor crank
provides coarse adjustment.

When approaching the end stops of the roller inductor
(readings of Zero or 279) SLOW DOWN. Slamming the
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.

BAND

160 M

80 M

40 M

20 M

15 M

12 M

10 M

INPUT SWITCH SETTING INDUCTOR

SUGGESTED ACTUAL HI-C/LO-C HI-Z/LO-Z SUGGESTED ACTUAL

66

35

20

11

35

18

15

HI-C

HI-C

HI-C

HI-C

HI-C

HI-C

HI-C 240

HI-Z

HI-Z

HI-Z

HI-Z

HI-Z

HI-Z

HI-Z

156

184

215

231

237

238

Page 8

To RESTORE wheel pressure on
the inductor push down on the
at springs soldered to the
wheel shaft located on each
end of the shaft.

PALSTAR

OPERATING YOUR BT1500A

9. When you have tuned your antenna to the best SWR, record

the settings of the INPUT, ANTENNA, and INDUCTANCE

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

acceptable. Check your transmitter/amplier manual for

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:

- highest FORWARD power reading

- lowest REFLECTED power reading

- uses the largest capacitance (highest number) on the

INPUT and ANTENNA controls.

NOTES:

4. Any time a new or dierent antenna is connected, it is

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

the rod to the roller coil body, as this will contaminate the

windings.

Page 9

PALSTAR