1. Amateur Radio & Electronics Projects:
144 MHz VHF Amplifier
Tri-Ex Tower Installation
Low Frequency DDS Transmitter
Denis P. Cote W1WV
Portfolio Presentation

2. VHF POWER AMPLIFIER
Overview
n Built 1995-1997
n 144-147 MHz
n CW & SSB Modes
n Class AB Operation
n 10 Watt RF Input
n 400 Watt RF Output
n Custom Machined &
Labeled Panels
n HV Safety Interlocks

3. Amplifier Documentation
Double 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

4. VHF POWER AMPLIFIER
Components Chassis
Screen / Grid / Filament Supply
4CX250R – Power TetrodeRF Deck & Tuning Controls
Tank Circuit Compartment

5. VHF POWER AMPLIFIER
High 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

6. VHF POWER AMPLIFIER
Power Supply Nomenclature
300 V DC Screen
and
Bias Supply
4KV HV
Transformer
12 & 9 Volt DC Low Voltage
TR Relay, Indicator Lamps,
Aux Relays
HV Filter
Capacitor Bank
Step Start Relays
HV metering shunt
(not visible)
Variac
HV
Rectifier Bridge

7. VHF POWER AMPLIFIER
Operational 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%

8. TRI-EX ANTENNA TOWER
Construction - 1999
Base Preparation
& Concrete Pour
Electric Winch Control
51’ Extended
Base Design
&
Fabrication
WT-51 Tower: 21’ Retracted Ht.

9. Antenna Tower

10. Concrete Tower Base – AutoCAD

11. Low Frequency DDS Transmitter
Construction

13. LF DDS Transmitter
Overview
n Atmel AT90S2313 DDS Chip
n Frequency 130 - 400KHz
n Operate 160-190KHz LF Band (LOWFER)
n Morse, QRSS (Slow CW), DFCW
n 1 Watt Output
n Stable 12.6 MHz TCXO
n PC Control via RS-232
n DDS Programmable via Parallel Converter &
Atmel Software

14. LF DDS Transmitter
Long Distant Receive Captures
Visual 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

15. LF DDS Transmitter
Transmit Antenna and Final
n 50’ x 50’ Vertical Loop Antenna
n LF Class D Final Transmitter
n Part 15 FCC – 1 Watt to TX Antenna
n DDS Transmitter used as Exciter

16. LF Transmit Antenna
TX ID ‘DPC’ Swansea, MA
LF Final Amp in Weather Tight Enclosure – 100’ from house
TX Loop Antenna

17. LF Final Amplifier
Class D Switching Amp
LF Final Amplifier Board
Undergoing Bench Testing & Tune Up
Square Wave – Amp Output
Sine Wave – Antenna Current

18. LF Receiving Equipment
23 Turn LF Receive Loop
23 Turn LF Receive Magnetic Loop
Low Frequency Receiver
Icom IC-R75 Receiver
Loop Tune Control & LP Filter
Antenna Rotor Control
PC 500MHz AMD: Argo V1 & SB16 soundcard

19. LF Receive Block Diagram
LF RX
IC-R75
Loop Tune
&
Pre-Selector
CRT
PC
w/
Sound
Card
500 KHz
LP
Filter
Loop Antenna
Aux.
Line Out
PC Running
Argo Software
Displayed
Information
As Received

20. LF CW Exciter
RS-232 Keyed
Oscillator Freq 173.5 KHZ
KID Keyer IC
12 VDC Supply Voltage
Point to Point Soldering
Vector Board

21. Back Up

22. RADIO ELECTRONICS PROJECTS
Amplifier Testing
Class D LF Final Amplifier Board
Output Waveforms LF Exciter Receive Antenna Relay Board

23. HAM RADIO EQUIPMENT

24. HF ANTENNAS/GROUND

25. n Rohn Telescoping Tower Refurbishment
2009-Present
70 foot Telescoping
Tower

26. n Rohn Telescoping Tower Refurbishment
2009-Present
Roller and Sheave Machining