Antennas%20for%20Restricted%20Space

1
Antennas for Restricted Space

• Two Unusual Examples
• _at_ W5JAW

2
Why?

• Necessity
• Challenging
• Educational (An excuse to play with modeling
  software and other tools)
• Its Fun!

3
To Understand Why.
4
To Understand Why.Contd
5
Initial Goals

• Single all band antenna for 80-10m, including
  WARC bands
• Fit within width of house (no external supports
  available
• Semi stealth

6
EZNEC Main Window
7
EZNEC Example
8
Phase 1 Solution Bent Carolina Windom
9
Dimensions of C.Windom

• Horizontal 42 ft (25 17 ft)
• Left Vertical Section 16 ft
• Right Vertical Section 8 ft
• Center Vertical Section 10 ft
• Height 30 ft

10
C.Windom Performance

• Acceptable on 40-10m
• Terrible on 80m (as expected)

11
SWR and Feedpoint Effects
134 ft dipole
154 ft dipole
12
80m Modification Bent Carolina Windom
13
80m Modification

• 75 uHy inductor (4 Air Dux)
• 12 ft vertical wire at 8 ft bend

14
Current Distribution80m
15
80m Azimuth Plot
16
80-10m Results(100 Watts)
17
160 Meter???

• Good enough to work a few mults during contests
• Semi stealth

18
160m ProjectModel 1

• Quick and simple 1-2 day project
• Model on EZNEC
• Collect parts
• Install
• Try it out (Stew Perry)

19
160m 1 Front View
20
160m 1 Side View
21
EZNEC Model 1
22
Elevation Gain 8ft 160m
23
Results with Model 1

• Worked 43 States, 5 VE Provinces and 6 countries
  that night
• Worked 45 countries over the rest of the winter,
  on all continents
• Decided to try improvements for next season

24
Design Goals for Model 2

• Raise base above edge of 2nd level roof
• Add some length to vertical section
• Design and build Auto Tuner (ATU) to cover entire
  band
• Build into and use resources of LDG Auto Tuner

25
Auto Tuned 160m AntennaMajor Tasks and Project
Flow

• Model antenna (EZNEC) 3 Weeks-- Compare to
  old antenna-- Determine tuning requirements
• Mechanical design and build of antenna Few
  Days
• Design and build the base loading unit 3
  Weeks-- Mechanical-- Electrical

26
Auto Tuned 160m AntennaMajor Tasks and Project
Flow

• Design and build the Controller 2 months
• -- Select microcontroller (PIC)
• -- Study and understand PIC resources
  Hardware resources (I/O, A/D, Timers, etc)
  Instruction set and SW configuration
  Development tools (Microchip IDE)
• -- Design electronics
• -- Preliminary logic flow diagram
• -- Develop firmware
• -- Run simulations on PC and debug
• -- Build electronics boards
• -- Modify LDG tuner to provide electrical and
  mechanical interface to Controller
• -- Assemble Controller into LDG tuner

27
Auto Tuned 160m AntennaMajor Tasks and Project
Flow

• Test and debug total system Few Hours
• -- Program PIC via Microchip ICD2
• -- Step through program to test all functions
• -- Debug and reassemble until system
  performs as planned
• Add Phase II features, debug and test
  1 Week
• Final documentation 3 Days

28
Radiation Efficiency

• Rtotal RradiationRcoilRgroundRenvironment
• Efficiency 100 x Rradiation / Rtotal

29
160m 2 Front View
30
160m 2 Side View
31
160m 12 ft Simple Model
32
Elev. Pattern Simple Model
33
SWR Simple Model 12 ft
34
12 ft 160m Model w/ Roof
35
12 ft 160m Vertical SWR
36
12 ft 160m Elev Pattern
37
Gain Comparisons
38
K5NA
VS. W5JAW
39
The Farm --1
40
The Farm --2
41
AUTOTUNERFUNCTIONAL OVERVIEW

• Use the existing pushbutton switches on the LDG
  Tuner to interface with the PIC Controller to set
  mode of operation
• Provide switching between primary antenna and 160
  m
• Control keying of transceiver during tuning
• Allow manual tuning of 160 m antenna
• Provide one button semi-automatic tuning on 160m

42
AUTOTUNERFUNCTIONAL OVERVIEW

• Provide optional automatic tuning on 160m,
  activated by sensing SWR
• Measure frequency change to provide proper
  initial direction to motor drive
• Provide digital filtering of SWR measurement
  during tuning to eliminate noise caused by
  antenna movements due to wind

43
AT External Unit
44
External Unit Schematic
45
AT Internal Mechanism
46
AT Inside View
47
AT Inside View
48
AT Input End Cap
49
PIC Controller PCB Schematic
50
PIC PCB
51
Relay PCB Schematic
52
Relay PCB
53
Controller in LDG ATU
54
ATU Front View
55
PIC MPLAB IDE
56
N5TW 160M Challenge

• K5NA 274/1352.09
• N5TW 177/1351.31
• W5JAW 71/125.92

Score Countries/Radiator Length (countries per
foot)
57
Success with Small LF Ants.

• Dont be constrained to conventional
  configurations
• Minimize losses in system
• Use modeling tools
• Be in right place at right time
• Be patient

58
Ice? No Problem!