RF Linear Amplifier PCB Assembly Manual DX300 Revsion A PCB...RF Linear Amplifier PCB Assembly Manual SkyWave DX300 Revision-A Last Revised - 12/25/2020 5:05 AM Page 5 of 53 Quantity

RF Linear Amplifier PCB Assembly Manual

SkyWave DX300 Revision-A

Last Revised - 12/25/2020 5:05 AM

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www.telstar-electronics.com

http://www.telstar-electronics.com/



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Table of Contents

Introduction ...................................................................................................................................... 3

Required Parts List ............................................................................................................................. 4

Before You Start ................................................................................................................................ 6

Assembly Instructions ......................................................................................................................... 7

Step #1 - Spacer (SPACER1, SPACER2, SPACER3, SPACER4) ................................................................ 7

Step #2 - Fixed Resistor (R1 through R23) ......................................................................................... 9

Step #3 - Variable Resistor (VR1) .................................................................................................... 11

Step #4 – Diode (D1 through D5) ................................................................................................... 13

Step #5 – Bead Inductor (L2 & L3) .................................................................................................. 15

Step #6 - Electrolytic Capacitor (C1, C2, C7, C8,) ............................................................................. 17

Step #7 - Ceramic Capacitor (C3, C4, C5, C6, C9, C10, C11, C12, C13, C14, C16) ................................ 19

Step #8 - Fuse Holder (F1) ............................................................................................................. 21

Step #9 - Relay (RLY1) .................................................................................................................. 23

Step #10 - Toroid RF Choke (L1) ..................................................................................................... 25

Step #11 - Field Effect Transistor (Q2, Q3) ....................................................................................... 27

Step #12 – Operational Amplifier (U2) ............................................................................................. 29

Step #13 - Voltage Regulator (U1) .................................................................................................. 31

Step #14 – Field Effect Power Transistor (Q1) ................................................................................... 33

Step #15 – Bipolar Power Transistor (Q5) ........................................................................................ 35

Step #16 – Air Inductor (L4) .......................................................................................................... 37

Step #17 – Mica Trimmer Capacitor (C15) ........................................................................................ 39

Step #18 – Field Effect RF Power Transistor (Q4) .............................................................................. 41

Step #19 – Coaxial Cable ............................................................................................................... 43

Step #20 - Switch, LED, and DC Power Wiring .................................................................................. 44

Step #20 - PCB Mounting to Heat Sink ............................................................................................. 45

Step #21 - Bias Adjustment............................................................................................................ 48

Step #22 - C15 Adjustment ............................................................................................................ 49

Step #23 – Amplifier Operation ....................................................................................................... 50

Troubleshooting ............................................................................................................................... 51

Specifications .................................................................................................................................. 52

RF Performance ............................................................................................................................... 53




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Introduction

Congratulations on your purchase of the new SkyWave DX300 RF Amplifier PCB. This PCB is a result of

quality engineering to provide high performance and reliability.

Listed below are some of the key features:

High Reliability Design

+48VDC Operation

All Mode (AM, FM, SSB)

26-30MHz Frequency Coverage

LDMOS MRF300 Single-Ended Tuned Configuration

Class-AB Temperature-Tracking Bias

High Output Power / Low Harmonic Content

Carrier Operated or Manual* Transmit / Receive Switching

Continuous Reverse Voltage Protection without Damage to Amplifier or Fuse

Fuse Protected

Selectable SSB Delay

Power and Transmit Indicators

Low Stand-By Power Consumption

Premium Quality Components & Printed Circuit Board

We have developed a logical step-by-step procedure that we hope will make your assembling experience

efficient & pleasurable…

* Contact Telstar Electronics for details on using the “manual switching” feature.




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Required Parts List

Quantity Description Reference

24” Cable, Coaxial, RG174A/U Type, 52-Ohm RF IN, RF OUT

8 Capacitor, Ceramic, 0.01uF, 100V, 20%, Z5U, Radial C3, C6, C9, C11, C12, C13,

C14, C16

2 Capacitor, Ceramic, 0.1uF, 100V, 20%, Z5U, Radial C4, C5

1 Capacitor, Electrolytic, 100uF, 25V, 20%, Radial C8




1 Capacitor, Ceramic, 560PF, 100V, 5%, NP0, Radial C10

1 Capacitor, Mica Compression, 175pF-680pF, 175V, TH C15

2 Diode, High Speed Signal, 1N914, DO35, Axial D1, D2

1 Diode, Zener, 10V, 0.5W, DO-35 D3

1 Fuse Holder, ATC Type, TH F1

1 Fuse, ATC, 15A F1

1 IC, Operational Amplifier, LM2904, Dual, DIP-8 U2

1 Inductor, Air L4

2 Inductor, RF Choke, 500-Ohms@30MHz, Wound Bead, Axial L2, L3

2 Insulator, Phase Change, TO-220 INSUL1, INSUL2

1 PCB, SkyWave DX300 Revision-A N/A

1 Potentiometer, 1K, 0.1W, Vertical Adjust, TH VR1

1 Regulator, Voltage, Adjust, 60V, 1.5A, TO-220 U1

1 Relay, DPDT, 12V, 8A, DIP RLY1

1 Resistor, Carbon Film, 1.2K, 0.25W, 5%, Axial R16

1 Resistor, Carbon Film, 100, 0.25W, 5%, Axial R5

3 Resistor, Metal Film, 10K, 0.25W, 1%, Axial R2, R8, R12

4 Resistor, Carbon Film, 10K, 0.25W, 5%, Axial R6, R9, R17

4 Resistor, Carbon Film, 1K, 0.25W, 5%, Axial R7, R14, R15, R20

1 Resistor, Metal Film, 3.3K, 0.25W, 1%, Axial R3


1 Resistor, Carbon Film, 47K, 0.25W, 5%, Axial R10


1 Resistor, Carbon Film, 560, 0.25W, 5%, Axial R18


2 Resistor, Carbon Film, 820, 0.25W, 5%, Axial R1, R13

1 Resistor, Metal Oxide, 10, 2W, 5%, Axial R23






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Quantity Description Reference

3 Screw, Machine, Philips Pan Head, #4-40, 1/4", Stainless Steel N/A



4 Spacer, Round, 0.250"D, 0.125"ID, 0.100" Thick SPACER1, SPACER2,

SPACER3, SPACER4

1 Thermal Compound, 8.5W/mk, 0.5-gram Q4

1 Toroid, 0.825"OD, 0.520"ID, 0.250"W, #43 Material L1

1 Transistor, FET, N-Channel, MRF300AN, 250MHz, 50V, 300W, TO-247 Q4

1 Transistor, FET, N-Channel, 2N7000, TO-92 Q3

1 Transistor, FET, P-Channel, SUP70101EL, 100V, 120A, TO-220 Q1

1 Transistor, FET, P-Channel, TP0606, TO-92 Q2

1 Transistor, NPN, 3055, 60V, 10A, TO-220 Q5

2 TVS, Uni-Directional, DO-15 D4, D5

1 Washer, Locking, Split-Ring, #4, Stainless Steel N/A

3 Washer, Shoulder, Black Plastic Insulating, TO-220 WASHER1, WASHER2,

WASHER3

14” Wire, AWG#14, Teflon, Red, Stranded L1

24” Wire, Zip Cord, #12, Red/Black N/A

24” Wire, #22, Teflon, Blue, Stranded LED1, LED2

24” Wire, #22, Teflon, Yellow, Stranded LED1, LED2

24” Wire, #22, Teflon, Green, Stranded S1

24” Wire, #22, Teflon, Purple, Stranded S2




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Before You Start

This kit assumes a basic understanding of electronics, soldering, and operation of hand tools. In addition

to basic hand tools, the following items will be required for proper assembly.

PCB Assembly:

Soldering Iron†

Electronic Solder‡

7/64” Drill Bit (Alignment of SPACER1, SPACER2, SPACER3, SPACER4)

Small Scrap Piece of Wood (Alignment of SPACER1, SPACER2, SPACER3, SPACER4)

Needle-Nose Pliers

Diagonal Cutting Pliers

Wire Stripper

Pocket Knife or Equivalent (Scraping Enamel Coating of L4)

PCB Assembly to Heat Sink:

Heat Sink (See Page 45 for Suggested Sources)

Power Drill

#4-40 Tap (Mounting Holes in Heat Sink)

#42 Drill Bit (Mounting Holes in Heat Sink)

Masking Tape

Transfer Punch

Bias Adjustment:

48VDC Power Supply

Ammeter (Capable of 100mA)

Several Jumper Wires w/ Alligator Clips

Final RF Output Adjustment:

48VDC Power Supply (Capable of 15-Amps)

RF Wattmeter (Capable of Measuring 300W)

RF Dummy Load (Capable of Dissipating 300W)

Flat-Blade Screwdriver (Adjustment of C15)

Please take a few minutes before you begin assembling to review the entire assembly &

adjustment procedure.

A few things to remember during the assembly:

Several components in this design are sensitive to static electricity. Precautions should be taken to

avoid static buildup during assembly by using a grounded workstation mat and wrist band.

References are made to the top and bottom side of the PCB. The top side contains the printed

reference designators and component outlines. Most components are inserted from top and

soldered from the bottom. Follow the specific instructions given in each assembly step.

If at any time, you are unsure how to perform an assembly step or have a question, email us for

assistance at [email protected]

† 35W-65W recommended. Temperature controlled soldering equipment is always preferred. ‡ Solder recommendation is Kester 331. This solder has a flux that can be washed off with warm tap-water.




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Assembly Instructions

Step #1 - Spacer (SPACER1, SPACER2, SPACER3, SPACER4)

Locate the four positions on the bottom of the PCB where the spacers will be attached. (Figure 1)

Drill a 7/64” hole into a scrap piece of wood. (Figure 2)

With the aid of the 7/64” drill bit, position the drill bit shank§ through a spacer and through the

hole in the PCB into the piece of wood below. The drill bit will aid in centering the spacer on the

PCB hole during the soldering process. (Figure 3)

IMPORTANT - MAKE CERTAIN THE SPACERS ARE FLAT AGAINST THE BOTTOM SIDE OF THE PCB

BEFORE SOLDERING INTO POSITION. USE A MINIMAL AMOUNT OF SOLDER

MAKING CERTAIN NOT TO OBSTRUCT THE INNER HOLE.

Solder spacers into position.

Figure 1

§ The drill bit shank is the solid portion that does not contain the spiral cutting flutes.




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Details of hole drilled in wood.

Figure 2

Details of spacer installation.

Figure 3




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Step #2 - Fixed Resistor (R1 through R23)

IMPORTANT - FIXED RESISTORS HAVE NO POLARITY AND CAN BE INSTALLED IN EITHER

DIRECTION. MAKE CERTAIN THE RESISTORS ARE FULLY SEATED IN THE PCB

BEFORE SOLDERING.

Install resistors into the PCB at the designated locations. (Figure 4)

Solder resistors into position.

Cut off the excess lead length.

Figure 4




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Details of fixed resistor installation.

Figure 5




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Step #3 - Variable Resistor (VR1)

IMPORTANT - VARIABLE RESISTORS ARE POLARIZED AND MUST BE INSTALLED IN THE PROPER

ORIENTATION. MAKE CERTAIN THE RESISTOR IS FULLY SEATED IN THE PCB

BEFORE SOLDERING.

Insert variable resistor into the PCB at designated location. (Figure 6)

Solder variable resistor into position.


Figure 6




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Details of VR1 installation.

Figure 7




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Step #4 – Diode (D1 through D5)

IMPORTANT - DIODES ARE POLARIZED AND MUST BE INSTALLED IN THE PROPER

ORIENTATION. THE WHITE BAND INDICATED ON THE PCB INDICATES THE

CATHODE. THIS POLARITY BAND IS ALSO PRESENT ON THE DIODE ITSELF. MAKE

CERTAIN THE DIODES ARE FULLY SEATED IN THE PCB BEFORE SOLDERING.

Insert diodes into the PCB at the designated locations. (Figure 8)

Solder diodes into position.


Figure 8




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Details of diode installation.

Figure 9




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Step #5 – Bead Inductor (L2 & L3)

IMPORTANT - INDUCTORS ARE NOT POLARIZED SO THEY CAN BE INSTALLED IN EITHER

DIRECTION. MAKE CERTAIN L2 AND L3 ARE FULLY SEATED IN THE PCB BEFORE

SOLDERING.

Insert inductors into the PCB at the designated locations. (Figure 10)

Solder inductors into position.


Figure 10




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Details of L2 & L3 installation.

Figure 11




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Step #6 - Electrolytic Capacitor (C1, C2, C7, C8,)

IMPORTANT - ELECTROLYTIC CAPACITORS ARE POLARIZED AND MUST BE INSTALLED IN THE

PROPER ORIENTATION. THESE CAPACITORS HAVE MARKINGS INDICATING THE -

(NEGATIVE) TERMINAL. THE PCB INDICATES CAPACITOR POLARITY BY

DISPLAYING A + (POSITIVE) SYMBOL CLOSEST TO THE POSITIVE TERMINAL OF

THE CAPACITOR. MAKE CERTAIN THE CAPACITORS ARE FULLY SEATED IN THE

PCB BEFORE SOLDERING.

Insert electrolytic capacitors into the PCB at the designated locations. (Figure 12)

Solder capacitors into position.


Figure 12




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Details of C1 & C2 installation.

Figure 13

Details of C7 & C8 installation.

Figure 14




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Step #7 - Ceramic Capacitor (C3, C4, C5, C6, C9, C10, C11, C12, C13, C14, C16)

IMPORTANT - CERAMIC CAPACITORS ARE NOT POLARIZED AND CAN BE INSTALLED IN EITHER

DIRECTION.

Insert ceramic capacitors into the PCB at the designated locations. (Figure 15)

Solder capacitors into position.


Figure 15




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Details of ceramic capacitor installation.

Figure 16




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Step #8 - Fuse Holder (F1)

IMPORTANT - FUSE HOLDERS ARE NOT POLARIZED AND CAN BE INSTALLED IN EITHER

DIRECTION. MAKE CERTAIN THE FUSE HOLDER IS FULLY SEATED IN THE PCB

BEFORE SOLDERING.

Insert fuse holder into the PCB at the designated location. (Figure 17)

Solder the fuse holder into position.


Figure 17




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Details of F1 (fuse holder) installation.

Figure 18




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Step #9 - Relay (RLY1)

IMPORTANT - RELAYS ARE POLARIZED AND MUST BE INSTALLED IN THE PROPER

ORIENTATION. MAKE CERTAIN THE RELAY IS FULLY SEATED IN THE PCB BEFORE

SOLDERING.

Insert relay into the PCB at the designated location. (Figure 19)

Solder relay into position.


Figure 19




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Details of RLY1 installation.

Figure 20




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Step #10 - Toroid RF Choke (L1)

IMPORTANT – RF CHOKES ARE NOT POLARIZED AND CAN BE INSTALLED IN EITHER

DIRECTION. THIS CHOKE WILL REQUIRE WINDING OF A LENGTH OF RED AWG

#16 WIRE ONTO THE TOROID FERRITE CORE.

Wind ten complete turns through the toroid core.

Cut and strip wire ends.

Solder choke to top of PCB at the designated location. (Figure 21)

Figure 21




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Details of L1 installation.

Figure 22




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Step #11 - Field Effect Transistor (Q2, Q3)

IMPORTANT - TRANSISTORS ARE POLARIZED AND MUST BE INSTALLED IN THE PROPER

ORIENTATION. USE THE OUTLINE ON THE PCB AS A GUIDE TO INSTALL THE

TRANSISTORS WITH THE FLAT SIDE AS SHOWN.

Insert transistors into the PCB at the designated locations. (Figure 23)

Solder transistors into position.


Figure 23




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Details of Q2 & Q3 installation.

Figure 24




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Step #12 – Operational Amplifier (U2)

IMPORTANT – INTEGRATED CIRCUITS ARE POLARIZED AND MUST BE INSTALLED IN THE

PROPER ORIENTATION. USE THE OUTLINE ON THE PCB AS A GUIDE TO INSTALL

THE INTEGRATED CIRCUIT WITH THE NOTCHED SIDE AS SHOWN.

Insert operational amplifier into the PCB at the designated location. (Figure 25)

Solder operational amplifier into position.


Figure 25




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Details of U2 installation.

Figure 26




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Step #13 - Voltage Regulator (U1)

IMPORTANT - VOLTAGE REGULATORS ARE POLARIZED AND MUST BE INSTALLED IN THE

PROPER ORIENTATION.

Form the leads of the voltage regulator at a 90-degree angle, 0.25” from the bottom of the plastic

body. (Figure 28)

Insert voltage regulator from the bottom of the PCB so the leads protrude upward through the

holes.

Place the PCB on a flat surface with the regulator in position and solder from the top of the PCB.


Figure 27




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Details of lead forming.

Details of U1 installation.

Figure 29

Figure 28




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Step #14 – Field Effect Power Transistor (Q1)


ORIENTATION.

Form the leads of the transistor at a 90-degree angle, 0.25” from the bottom of the plastic body. (Figure 31)

Insert transistor from the bottom of the PCB so the leads protrude upward through the holes.

Place the PCB on a flat surface with the transistors in position and solder from the top of the PCB.


Figure 30




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Figure 31

Details of Q1 installation.

Figure 32




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Step #15 – Bipolar Power Transistor (Q5)


ORIENTATION.





Figure 33




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Figure 34


Figure 35




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Step #16 – Air Inductor (L4)

IMPORTANT - INDUCTORS ARE NOT POLARIZED AND CAN BE INSTALLED IN EITHER

DIRECTION.

Apply solder to the PCB pads of L4. (Figure 36)

Apply solder to the ends of air inductor L4. It will be necessary to use a knife to scrape the enamel

coating to get the solder to adhere.

Solder L4 in position on top of PCB in the designated location, holding it in place using a needle

nose pliers. (Figure 36)

Figure 36




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Details of L4 installation.

Figure 37




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Step #17 – Mica Trimmer Capacitor (C15)

IMPORTANT - CERAMIC CAPACITORS ARE NOT POLARIZED AND CAN BE INSTALLED IN EITHER

DIRECTION.

Insert trimmer capacitor into the designated location. (Figure 38)

Solder capacitor into position.


Figure 38




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Details of C15 installation.

Figure 39




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Step #18 – Field Effect RF Power Transistor (Q4)


ORIENTATION.





Figure 40




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Figure 41


Figure 42




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Step #19 – Coaxial Cable

IMPORTANT - COAXIAL CABLE IS POLARIZED AND MUST BE INSTALLED IN THE PROPER

ORIENTATION. THE BRAIDED PORTION OF THE CABLE IS ALWAYS ATTACHED TO

GROUND (GND).

Solder coaxial cables at the proper designated positions on top. (Figure 43)

Figure 43




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Step #20 - Switch, LED, and DC Power Wiring

The SkyWave DX300 has been designed to accommodate two switches** and two LED†† indicators.

Function Wiring Color

S1 (ON/OFF) – Amplifier Main Power Green and Green

LED1 – Main Power LED Indicator Yellow(+) and Blue

S2 (SSB DELAY) – SSB Delay Enable Purple and Purple

LED2 – Transmit LED Indicator Yellow(+) and Blue

Solder AWG#22 wires (S1, S2, LED1, LED2) at the proper designated locations. (Figure 44)

Solder AWG#12 “Zip-Cord” +48V (RED) and GND (BLACK) at the proper designated locations. (Figure 44)

Figure 44

** Switches should be SPST type capable of 100mA@25V minimum. †† LEDs can be any color/size and should be rated for an operating forward current of 20mA. The PCB has been marked with the “+” for orientation

connection purposes.




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Step #20 - PCB Mounting to Heat Sink

IMPORTANT - NOW THAT THE AMPLIFIER PCB HAS BEEN FULLY ASSEMBLED, IT MUST BE

MOUNTED TO A HEAT SINK BEFORE THE BIAS ADJUSTMENT CAN BE PERFORMED.

A HEAT SINK WITH A MAXIMUM THERMAL RESISTANCE OF 0.75 DEGREES

CENTIGRADE/WATT IS RECOMMENDED FOR CONVECTION APPLICATIONS‡‡.

Place the completed PCB on the heat sink. Use masking tape or equivalent to hold the PCB still

during the marking process. Using a transfer punch§§, carefully mark the center of the four PCB

mounting holes that contain the spacers, the RF transistor mounting hole, and the three device

mounting tab holes at the edge of the PCB. (Figure 45)

Figure 45

‡‡ There are several internet sites that sell extruded aluminum heat sinks designed for RF power amplifiers. Several are listed below. Telstar Electronics

takes no responsibility for the content of the links and does not endorse any specific product or service.

Communication Concepts – www.communication-concepts.com

Heatsink USA – www.heatsinkusa.com §§ A transfer punch is a punch of a specific outer diameter that is non-tapered and extends the entire length of the punch (except for the tip). It is used to

tightly fit the tolerances of an existing hole and, when struck, precisely transfer the center of that hole to another surface.

http://www.telstar-electronics.com/http://www.communication-concepts.com/http://heatsinkusa.com/



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Remove the tape and PCB from the heat sink. Use an automatic center punch to enhance the

marked centers prior to drilling. Use a #42 (0.0935”) drill bit to drill all marked centers.

Use a #4-40 tap to thread all eight drilled holes.

Position insulators (INSUL1 and INSUL2) on the heat sink so that they will make proper contact

with the metal tabs of Q1 and U1 and will align properly with the tapped mounting holes. (Figure 46)

Apply thermally conductive paste to the bottom of Q4.

IMPORTANT – DO NOT FORGET TO APPLY THERMALLY CONDUCTIVE PASTE TO Q4!

Hover the PCB over the mounting holes drilled in the heat sink. Lower the PCB straight down onto

the sink to avoid sliding the insulators.

Install loosely four 5/16” #4-40 machine screws in the four PCB mounting that have the metal

spacers below the PCB.

Figure 46




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IMPORTANT - PLASTIC INSULATING WASHERS ARE NOT SYMMETRICAL, AND MUST BE

ORIENTED AS SHOWN BELOW.

Install three plastic insulating washers (WASHER1, WASHER2, WASHER3) on three 1/4"long #4-40

machine screws and install the screws loosely for Q1, U1, Q5.

IMPORTANT - DON’T OVER-TIGHTEN SCREWS THAT CONTAIN THE PLASTIC INSULATING

WASHERS.

Install 3/8” long #4-40 machine screw with lock washer into Q4.

Starting with Q4, tighten all eight #4-40 screws to 6 in/lbs.




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Step #21 - Bias Adjustment

The SkyWave DX300 amplifier has been designed to operate with class-AB biasing.

IMPORTANT – TO KEEP AMPLIIER HARMONICS TO SPECIFIED LEVELS, THE BIAS MUST BE

ADJUSTED PRIOR TO THE AMPLIFIER BEING PUT INTO SERVICE.

Temporarily solder the two wires together from S1 (ON/OFF).

Insert the 15A fuse (F1).

Place an ammeter across jumper (JMP1) terminals.

Turn VR1 (BIAS) fully counterclockwise.

Temporarily connect RF IN (center conductor of coaxial cable) to LED1 (+ wire). The ground (braid)

of coaxial cable remains unconnected. This step will allow the relay to engage and a click will be

heard when power is applied in the following step.

Apply 48VDC to the amplifier.

Adjust VR1 (BIAS) slowly clockwise to obtain 100mA (+/-20mA) on the ammeter.

Disconnect all connections to power supply and ammeter.

IMPORTANT - THE TWO PADS ON JMP1 MUST BE SHORTED TOGETHER FOR THE AMPLIFIER TO

OPERATE PROPERLY.

Apply a liberal amount of solder to the jumper (JMP1) pads so a solder bridge is formed.




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Step #22 - C15 Adjustment

IMPORTANT – ADJUSTABLE MICA TRIMMER CAPACITORS NORMALLY HAVE A WORKING

ADJUSMENT RANGE IN A COMPRESSED (TIGHTENED SCREW) POSITION. PRE-

ADJUST THE CAPACITOR ONE TURN COUNTER-CLOCKWISE FROM THIS SNUG-

TIGHTENED POSITION BEFORE PROCEEDING TO THE ACTUAL ADJUSTMENT

PROCEDURE BELOW.

IMPORTANT - THE AMPLIFIER REQUIRES A DC POWER SOURCE CAPABLE OF 48V@15A TO

ACHIEVE MAXIMUM POWER OUTPUT.

Temporarily solder the two wires together from S1 (ON/OFF).

Hook the amplifier RF IN (50-Ohm coaxial cable) to the driving transmitter.

Hook the amplifier RF OUT (50-Ohm coaxial cable) to a suitable wattmeter & high-power dummy

load.


With the lowest RF drive available (above the 500mW minimum), key the transmitter in AM (DSB)

mode with no modulation and adjust C15 for a maximum value on the wattmeter.

Repeat the C15 adjustment again, this time adding modulation to the normal driving signal.

This concludes the adjustment procedure.




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Step #23 – Amplifier Operation

Install a SPST switch to the wiring coming from S1 (ON/OFF).

Install a SPST switch to the wiring coming from S2 (SSB DELAY).

Install an LED to the wiring coming from LED1 (POWER).

Install an LED to the wiring coming from LED2 (XMIT).

Hook the amplifier RF IN (50-Ohm coaxial cable) to the driving transmitter.

Hook the amplifier RF OUT (50-Ohm coaxial cable) to a suitable antenna.

IMPORTANT - MAKE CERTAIN THAT THE ANTENNA/FEEDLINE SWR IS 1.5:1 OR LOWER. AN

ELEVATED SWR WILL FORCE THE OUTPUT TRANSISTOR TO OPERATE AT A MUCH

HIGHER TEMPERATURE THAT COULD RESULT IN PREMATURE FAILURE.


Set S2 (SSB DELAY) switch to the “ON” position only if transmitter is in SSB mode.

Set S1 (ON/OFF) switch to the “ON” position.

The amplifier is now ready for operation.




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Troubleshooting

Problem Possible Cause Possible Solution

Amplifier does not operate

(Power switch S1 “ON” but

power indicator is not lit)

Power source not

connected.

Check connection to power

source.

Fuse missing or blown. Check F1.

Faulty wiring from S1

switch to circuit board.

Check wiring from S1 switch to

circuit board.

Amplifier does not operate

(Power switch S1 is “ON” and

power indicator lit)

Insufficient or no RF drive. Check transmitter and coaxial

cable to input of amplifier.

Relay engages on transmit but

amplifier has no output power. J1 open.

Check that J1 is properly

shorted with solder.

Relay chatters during SSB

operation.

Switch S2 is not closed. Move S2 switch to proper

position.

Faulty wiring from S2

switch to circuit board.

Check wiring from S2 switch to

circuit board.

Relay chatters during AM/FM

operation. Insufficient drive power. Increase drive power.

Amplifier keeps blowing fuse.

Plastic insulating washers

(WASHER1, WASHER2,

WASHER3) improperly

installed.

Check plastic insulating

washers on Q1 and U1.

Insulators (INSUL1,

INSUL2, INSUL3)

improperly installed.

Check insulators under Q1 and

U1.

Short Circuits.

Check for short circuits on top

and bottom of circuit board

from faulty soldering.

Check for short circuits from

bottom of circuit board to heat

sink.




Last Revised - 12/25/2020 5:05 AM

Page 52 of 53


Specifications

Parameter Conditions/Notes Value

Operating Modes - AM, FM, SSB

Voltage Requirements Typical +48VDC

Maximum +55VDC

DC Current Maximum 12A

RF Input Power Minimum 500mW

Maximum 20W (PEP)

RF Power Output Maximum 275W

2nd Harmonic Typical (150W CW@28MHz) -46dBc***

3rd Harmonic Typical (150W CW@28MHz) -80dBc

Input / Output Impedance††† Typical 50-Ohms

Input SWR‡‡‡ Typical 1.1:1

Power Gain Typical @28MHz 15dB

Characterized Bandwidth 0.5dB Gain Flatness 26-30MHz

Class-AB Bias Drain Current -20◦C to +100◦C Heat Sink

Temperature 100mA +/-15mA

Fuse ATO - Automotive Type 15A

SSB Relay Dropout Delay Typical 1.0 Second

Stand-By Power Typical 250mW

Reverse Voltage Protection No Damage to Amplifier or Fuse Continuous

PCB Solder Mask & Silkscreen Premium FR4

*** Decibels below carrier. ††† An antenna system with an SWR of 1.5:1 or less is critical for proper amplifier operation.

‡‡‡ Standing Wave Ratio.




Last Revised - 12/25/2020 5:05 AM

Page 53 of 53


RF Performance

35

70

105

140

175

210

240258

270 275

0

50

100

150

200

250

300

0 1 2 3 4 5 6 7 8 9 10 11

OU

TPU

T (W

ATT

S)

INPUT (WATTS)

Power Output @ 48V/28MHz

Documents

RF Linear Amplifier PCB Assembly Manual DX300 Revsion A PCB...RF Linear Amplifier PCB Assembly Manual SkyWave DX300 Revision-A Last Revised - 12/25/2020 5:05 AM Page 5 of 53 Quantity