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Off-Center Fed Dipoles презентация
Содержание
- 1. Off-Center Fed Dipoles
- 2. N1IW Why? Looking for solutions for low
- 3. N1IW Off Center Fed Dipole Basics Half
- 4. N1IW OCFD Data 80M Used for 10
- 5. N1IW Why They Work It’s just a
- 6. N1IW Current Distribution on a Dipole
- 7. N1IW Current & Voltage at Fundamental V I
- 8. N1IW I & V at 2nd Harmonic I V
- 9. N1IW I & V at 4th Harmonic I V (2X Expanded Scale)
- 10. N1IW I & V at 8th Harmonic I V (2X Expanded Scale)
- 11. N1IW But what about the 6th harmonic?
- 12. N1IW I & V at 6th Harmonic (Bad Dog!) I V (2X Expanded Scale)
- 13. N1IW And Odd Harmonics? Same problem: Current minimum
- 14. N1IW I & V at 3rd Harmonic (Bad Dog!) I V
- 15. N1IW Basic Gain Plots
- 16. N1IW 160M center fed dipole at 80 feet EL AZ
- 17. N1IW 160M OCFD at 80 feet AZ EL
- 18. N1IW 160M OCFD on 80M (x2) EL
- 19. N1IW 160M OCFD on 40M (x4) EL
- 20. N1IW 160M OCFD on 20M (x8) EL
- 21. N1IW 160M OCFD on 10M (x16) EL
- 22. N1IW Geometry/Height Old 80M design: 45.3 ft,
- 23. N1IW 4:1 Guanella Current Balun
- 24. N1IW 90’
- 25. N1IW 176’
- 26. N1IW 160M OCFD Normalized VSWR Plots
- 27. N1IW OCFD Orientation Issues
- 28. N1IW Single 160M OCFD at 125º, 160M/80M
- 29. N1IW Disclaimer… Your mileage may vary Batteries
N1IW Why? Looking for solutions for low band antennas Was abused by a counterpoise as a child Looking for multiband solutions Traditional low band wire arrays use dipoles or inverted vees
Слайд 2N1IW
Why?
Looking for solutions for low band antennas
Was abused by a counterpoise
as a child
Looking for multiband solutions
Traditional low band wire arrays use dipoles or inverted vees
Applications to driven & parasitic arrays
Looking for multiband solutions
Traditional low band wire arrays use dipoles or inverted vees
Applications to driven & parasitic arrays
Слайд 3N1IW
Off Center Fed Dipole Basics
Half wave resonant antenna at lowest frequency
of operation
Even Harmonic resonances (V/I ratio is approximately constant)
160M: 160, 80, 40, 20, 17, 12, 10
80M: 80, 40, 20, 10
Fed 1/3 of the way from the end vs. in the middle
Feed point impedance is approximately 200Ω
4:1 current balun does the trick
Even Harmonic resonances (V/I ratio is approximately constant)
160M: 160, 80, 40, 20, 17, 12, 10
80M: 80, 40, 20, 10
Fed 1/3 of the way from the end vs. in the middle
Feed point impedance is approximately 200Ω
4:1 current balun does the trick
Слайд 4N1IW
OCFD Data
80M
Used for 10 years
136 feet in length (located at abt
30 feet)
Fed 44.5 feet from one end
Resonant on 80M, 40M, 20M, 10M (no tuner)
160M (measured data)
Recent addition
264 feet long (located at abt 80 feet)
Fed 88 feet from one end; 4:1 homebrew balun
200Ω on 160M and 166Ω on 80M at resonance
2:1 BW: >200 kHz on 160M, 260 kHz on 80M
Fed 44.5 feet from one end
Resonant on 80M, 40M, 20M, 10M (no tuner)
160M (measured data)
Recent addition
264 feet long (located at abt 80 feet)
Fed 88 feet from one end; 4:1 homebrew balun
200Ω on 160M and 166Ω on 80M at resonance
2:1 BW: >200 kHz on 160M, 260 kHz on 80M
Слайд 5N1IW
Why They Work
It’s just a dipole!
But
½ wave resonant element, then harmonic
wire
Voltage/Current relationship at 1/3 feed point provides essentially constant ratio on even harmonics
Broadside null on harmonics
Voltage/Current relationship at 1/3 feed point provides essentially constant ratio on even harmonics
Broadside null on harmonics
Слайд 22N1IW
Geometry/Height
Old 80M design: 45.3 ft, 90.7 ft; 30 ft high
New 160M
design: 88ft, 176 ft; 80 ft high
Both use 4:1 Guanella balun design
80M variation: 45/65 ft flat+26 ft dropper
Feed point impedance at resonance drops as effective height above ground decreases
Recommend 1/3 λ up for 4:1 balun to work well
Both use 4:1 Guanella balun design
80M variation: 45/65 ft flat+26 ft dropper
Feed point impedance at resonance drops as effective height above ground decreases
Recommend 1/3 λ up for 4:1 balun to work well
Слайд 24N1IW
90’ Leg
45’ Leg
#12 stranded/insulated copper
4:1 Current Balun
(PVC enclosure)
~8 Wraps, covered with
heatshrink tubing
“Dogbone”
Insulator
Stainless hardware
UHF Connector
80M OCFD Construction Detail
Слайд 25N1IW
176’ Leg
88’ Leg
#12 stranded/insulated copper
4:1 Current Balun
(PVC enclosure)
~8 Wraps, covered with
heatshrink tubing
“Dogbone”
Insulator
Stainless hardware
UHF Connector
160M OCFD Construction Detail
Слайд 28N1IW
Single 160M OCFD at 125º, 160M/80M
How to deal with the broadside
null…
Rotate antenna to achieve best gain compromise
Rotate antenna to achieve best gain compromise
Europe (50º)
80M
160M
El of 30º
Слайд 29N1IW
Disclaimer…
Your mileage may vary
Batteries not included
Some assembly required
Professional driver, closed course
Void
where prohibited
Do not dispose of in fire
Taxes, titles, license fees extra
10M band openings longer than 2 hours require immediate medical attention
Do not dispose of in fire
Taxes, titles, license fees extra
10M band openings longer than 2 hours require immediate medical attention
