Real world comparison measurements clare ve3npc qcwa dinner nov 21 2006
This presentation is the property of its rightful owner.
Sponsored Links
1 / 48

HELIX ANTENNAS PowerPoint PPT Presentation


  • 296 Views
  • Uploaded on
  • Presentation posted in: General

REAL WORLD COMPARISON MEASUREMENTS Clare - VE3NPC QCWA Dinner Nov. 21, 2006. HELIX ANTENNAS. Early Helix – 2 x 10 Turns. 1989. 2 x 15 Turn 70 cm Helix . 1991 ?. AO-13 Antennas. About 1994. AO-40 Antennas. 2001. 13 and 23 cm Helix Arrays. 2003 .

Download Presentation

HELIX ANTENNAS

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Real world comparison measurements clare ve3npc qcwa dinner nov 21 2006

REAL WORLD COMPARISON

MEASUREMENTS

Clare - VE3NPC

QCWA Dinner Nov. 21, 2006

HELIX ANTENNAS


Early helix 2 x 10 turns

Early Helix – 2 x 10 Turns

1989


2 x 15 turn 70 cm helix

2 x 15 Turn 70 cm Helix

1991 ?


Ao 13 antennas

AO-13 Antennas

About 1994


Ao 40 antennas

AO-40 Antennas

2001


13 and 23 cm helix arrays

13 and 23 cm Helix Arrays

2003


So how did we do

So How Did We Do?

  • Only worked AO-40 in mode L/S

  • 6 other low orbiters were used by others

  • Used Yaesu FT-736R with 10 watts on L

  • There were 30 submissions

  • We made 102 QSO’s, nearly all on SSB

  • Placed 7th.


Ve3npc l s qso s ao 40

VE3NPC L/S QSO’s AO-40

  • AO-40 on mode L/S from 16 Sept 01 to 28 Jan 04

  • 10 watts output into 4 x 27 T helix array on the L uplink

  • Works out to about 1500 watts ERP

  • In that time I logged 832 QSO’s in mode L/S


More helix antenna operation

More Helix Antenna Operation

  • First satellite QSO in 1988

  • Now 18 years later have over 11 K Satellite QSO’s in log

  • With exception of mode A and K used in early RS satellites all were made using home brew helix ants for 70cm up and down links and 23 cm uplinks


So what

So What !

  • I have learned a lot about building and operating helix antennas.

  • They have worked very well on the air in competition with commercial crossed yagis, loop yagis and dishes that most satellite operators were and are using.

  • What my paper is about is that according to some published antenna modeling theory they should not have worked as well as the have.


The helix antenna

THE HELIX ANTENNA

  • Invented by Dr. John D Kraus in 1947

  • He constructed large arrays of helix antennas for radio astronomy


Helix antennas

  • “the dimensions of the helix are so non-critical that the helical beam antenna is one of the simplest types of antenna it is possible to make”

  • circumference

  • turn spacing (phase angle)

  • reflector size

  • conductor diameter

  • helix support (boom)


Kraus

Kraus

  • Gain (db)=10log3.325n

  • Linear function

  • Double n (turns) - double gain – 3 db

  • Four times n – four times gain – 6 db


Kraus1

Kraus

  • Satellite Experimenters Handbook

    0.8 > C > 1.2 C = circumference in wavelengths

    12 < a > 14 a = pitch angle in degrees

    But used C = 1 wavelength and a =12.5 degrees


V e3npc

V E3NPC

  • C = 1 wavelength

  • pa = 12.5 degrees


Helix antenna computer modeling nec

Helix Antenna Computer Modeling (NEC)

  • 1990 ARRL UHF/Microwave Experiments Manual – Bob Atkins KA1GT

  • 1995 ARRL Antenna Compendium - Emerson

  • 2005 Proceedings of the Southeastern VHF Society – Cebik W4RNL


Nec design theory

NEC Design Theory

The NEC designs concluded that :

- for a given number of turns there was a

particular value of circumference and

pitch angle that would provide peak gain.

- as the number of turns was increased the

increase in gain soon leveled off.


Bob atkins

Bob Atkins


Emerson

Emerson


Cebik

Cebik


Cebik1

Cebik


Emerson length

Emerson - Length


Consequences

Consequences

  • NEC modeling peak gain designs used in ARRL publications

  • Web page helix antenna calculators use NEC peak gain design formula

  • AMSAT “experts” come up with peak gain formula dimensions


Ve3npc 1990 or so

VE3NPC 1990 or so

  • Constructed several 70cm helix antennas following Bob Atkins design in the ARRL UHF/Microwave Experimenters Manual

  • They did not give any better performance.

  • Narrower band width and harder to get good feed match


Ve3npc 1992 93

VE3NPC – 1992/93

  • Constructed several different 2.4 GHz helix antennas and arrays for AO-13

    mode S

  • All were over 30 turns and most used Bob Atkins peak gain design

  • Didn’t work – never even heard beacon

  • Made 4 ft dish – worked like a charm


Summer 2005

Summer 2005

  • Dave VE3KL proposed constructing a 70cm helix antenna using the Emerson design

  • From my previous experience I questioned his choice

  • Dave was skeptical.

  • Well that started the ball rolling

  • Maybe I was wrong but I didn’t think so

  • Simple matter to compare his with mine

  • What appeared to be simple turned into a major project

  • Constructed and compared 10 different helix antenna


Objectives

Objectives

  • 1 To compare the peak gain design verses the simple Kraus design.

  • 2 To test the validity of the difference in gain relative to the number of turns (length in wavelengths).

  • 3 To test the effects of different boom materials.


Test equipment set up

Test Equipment Set Up


Antenna test range

Antenna Test Range


Helix antennas

Comparison Results Between Four Kraus Design Helix Antennas of Increasing length. C = 1 w/l P.A.= 12.5 deg.


Gain directivity

Gain & Directivity

  • An antenna may be very directive i.e. exhibit a narrow forward beam width but due to the configuration of the side lobes and/or degree of losses, provide higher or lower forward gain


Kraus 12 5 cm increased turns

Kraus 12.5 cm-Increased Turns

12 turns

6.5 turns

26 turns

52 turns


Increasing turns gain differences

Increasing Turns/Gain Differences


Comparison results between kraus design and emerson design

Comparison Results Between Kraus Design and Emerson Design


70 cm 10 turn kraus emerson

70 cm 10 Turn Kraus/Emerson

Kraus 10 turns

Emerson 10 turns


12 5 cm 2 88 w l kraus emerson

12.5 cm 2.88 w/l Kraus/Emerson

Emerson 12 turns

Kraus 13 turns


12 5 cm 5 75 w l kraus emerson

12.5 cm 5.75 w/l Kraus/Emerson

Kraus 26 turns

Emerson 24 turns


Kraus design different boom materials

Kraus Design – Different Boom Materials


Conclusions

Conclusions

  • Casts serious doubt on NEC computer modeling of helix antennas

  • Ant based on modeling doesn’t give predicted peak gain

  • 30 Turn helix ants can be made that will give real gain. Useful gain with 52 turns.

  • Aluminum or PVC OK for boom


Other verification

Other Verification

  • Can find no other information on direct experimental evidence to verify the computer modeling results of helical antennas !


Helix antennas

Questions ? ? ?


Ve3npc 23cm array constructed by kb9ups

VE3NPC 23cm Array Constructed by KB9UPS

VE3NPC

KB9UPS


Who cares

WHO CARES !!

  • Checked my satellite QSL cards

  • 40 % did not list type of ant

  • Of the 1267 cards listing type of antenna only 37 used a helix (3%)

  • Only 3 were in the US

  • One VK,FY and FP

  • The rest European (G3RUH pattern?)

  • 22 countries


G3ruh james miller

G3RUH – James Miller

  • 1993 published design for 16 turn 2401 MHz helix

  • C = 1.06 wavelengths

  • P.A. 12.5 degrees

  • 3.3 mm copper wire conductor

  • Boom 1 x 1 inch aluminum

  • Measured gain (sun noise) = 15.2 dbic

  • Kraus gain = 17.3 dbic


Central states vhf society antenna range tests 1995 2006

Central States VHF Society Antenna Range Tests 1995-2006

  • 15 helix antennas for 70cm, 33cm,23cm and 13cm measured

  • 2 met the theoretical (VE3KSK) – G3RUH design

  • 5 within 1 – 3 db

  • 8 within 4 – 11 db

  • Where theoretical = Kraus gain minus 3 db


Southeastern vhf society antenna range tests 2006

Southeastern VHF Society Antenna Range Tests 2006

  • 2 helix antennas tested at 2304 MHz

  • One 27 turn and one 16 turn.

  • Both about 1 db less than Kraus gain minus 3 db


Ao 40 orbit

AO-40 Orbit

60 k kilometers


  • Login