Amateur Radio & Electronics Projects:

144 MHz VHF AmplifierTri-Ex Tower InstallationLow Frequency DDS Transmitter

Denis P. Cote W1WVPortfolio Presentation

VHF POWER AMPLIFIEROverview

n Built 1995-1997n 144-147 MHz n CW & SSB Modesn Class AB Operationn 10 Watt RF Inputn 400 Watt RF Outputn Custom Machined &

Labeled Panelsn HV Safety Interlocks

Amplifier DocumentationDouble Click to Open Files

Microsoft Word Document

Detailed Description Write Up

Amp Fig. 1 HV PS Fig. 2a LV PS Fig. 2b Tube Data Sheet

VHF POWER AMPLIFIERComponents Chassis

Screen / Grid / Filament Supply

4CX250R – Power TetrodeRF Deck & Tuning Controls

Tank Circuit Compartment

VHF POWER AMPLIFIERHigh Voltage Tube Supply

n HV Plate Supply – 4 KV 0.5A Output

n HV Adjustable via Autotransformer (Variac)

n Nominal Voltage 2 KV

n Step-Start Inrush Protection

n 300V Screen Supply

n Adjustable Grid Bias

n Low Voltage Supplies: T/R Relay, Indicator Lamps & Auxiliary Relays

VHF POWER AMPLIFIERPower Supply Nomenclature

300 V DC Screen and

Bias Supply

4KV HV Transformer

12 & 9 Volt DC Low VoltageTR Relay, Indicator Lamps, Aux Relays

HV Filter Capacitor Bank

Step Start Relays

HV metering shunt (not visible)

Variac

HV Rectifier Bridge

VHF POWER AMPLIFIEROperational Parameters – On Air Test

Plate Voltage (No Load): 2200 VDC

RF Input Power: 640W

Plate Voltage (Load): 1600 VDC

RF Output Power: 390-400W

Plate Current (No Load): 90-100 mA

Drive Input: 8-10W

Plate Current (Load): 390-400 mA

Plate Dissipation: 240-250W

Screen Current (Load): 30 mA

Class of Operation: AB1

Grid Current (Load): 0-1 mA

Efficiency: 62.5%

TRI-EX ANTENNA TOWERConstruction - 1999

Base Preparation& Concrete Pour

Electric Winch Control

51’ Extended

Base Design &

FabricationWT-51 Tower: 21’ Retracted Ht.

Antenna Tower

Concrete Tower Base – AutoCAD

Low Frequency DDS TransmitterConstruction

LF DDS TransmitterOverview

n Atmel AT90S2313 DDS Chipn Frequency 130 - 400KHzn Operate 160-190KHz LF Band (LOWFER)n Morse, QRSS (Slow CW), DFCW n 1 Watt Outputn Stable 12.6 MHz TCXO n PC Control via RS-232n DDS Programmable via Parallel Converter &

Atmel Software

LF DDS TransmitterLong Distant Receive CapturesVisual Morse Code Representation

Receptions Courtesy of:

W1TAG (John Andrews) Andover, MA (Left)

W3EEE (Steve Dove) Elm, PA (Right)

Extremely weak signals – inaudible through receiver speaker !

QRSS/DFCW FFT Receive Software:

Argo V1 Build 1.34 courtesy Alberto, I2PHD

www.weaksignals.com

Soundcard based receive software

LF DDS TransmitterTransmit Antenna and Final

n 50’ x 50’ Vertical Loop Antennan LF Class D Final Transmittern Part 15 FCC – 1 Watt to TX Antennan DDS Transmitter used as Exciter

LF Transmit AntennaTX ID ‘DPC’ Swansea, MA

LF Final Amp in Weather Tight Enclosure – 100’ from house

TX Loop Antenna

LF Final AmplifierClass D Switching Amp

LF Final Amplifier BoardUndergoing Bench Testing & Tune Up

Square Wave – Amp OutputSine Wave – Antenna Current

LF Receiving Equipment

23 Turn LF Receive Loop

23 Turn LF Receive Magnetic Loop

Low Frequency Receiver Icom IC-R75 ReceiverLoop Tune Control & LP FilterAntenna Rotor ControlPC 500MHz AMD: Argo V1 & SB16 soundcard

LF Receive Block Diagram

LF RXIC-R75

Loop Tune&

Pre-Selector

CRTPCw/

SoundCard

500 KHzLP

Filter

Loop Antenna

Aux.Line Out

PC Running Argo Software

Displayed InformationAs Received

LF CW Exciter

RS-232 Keyed Oscillator Freq 173.5 KHZKID Keyer IC12 VDC Supply VoltagePoint to Point SolderingVector Board

Back Up

RADIO ELECTRONICS PROJECTS

Amplifier Testing Class D LF Final Amplifier Board

Output Waveforms LF Exciter Receive Antenna Relay Board

HAM RADIO EQUIPMENT

HF ANTENNAS/GROUND

n Rohn Telescoping Tower Refurbishment2009-Present

70 foot TelescopingTower

n Rohn Telescoping Tower Refurbishment2009-Present

Roller and Sheave Machining