best antenna

[YSWG]

As I stated, only those who feed via Linux (T feeder) or FR24 FlightFeeder (F feeder). Those using Windows FR24 uploader don't have the stats page. Can't comment if PlanePlotter feeders to FR24 have it or not.

[abcd567]

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Note: Tapatalk does not display Tables properly, Browsers do.
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QUICK REFERENCE TABLES

FORMULAS:

Item	Formula	Example Antenna 50 Ohm, Receiver 75 Ohm
Reflection Coefficient Γ	Γ = (Z1 - Z2) / (Z1 + Z2)	Γ = (75 - 50) / (75 + 50) = 0.2
Standing Wave Ratio SWR	SWR = {(1+Γ) / (1-Γ)} : 1	SWR = {(1+0.2) / (1-0.2)} : 1 = 1.5 : 1
Mismatch Loss ML dB	ML = -10 log (1 - Γ2)	ML = -10 log (1 - 0.22) = 0.177 dB

CALCULATED VALUES:

Reflection Coefficient	0.00	0.10	0.15	0.20	0.25	0.30	0.35	0.40	0.45	0.50	0.55	0.60	0.65	0.70	0.75	0.80	0.85	0.90	0.95	1.00
SWR	1.00	1.22	1.35	1.50	1.67	1.86	2.08	2.33	2.64	3.00	3.44	4.00	4.71	5.67	7.00	9.00	12.33	19.00	39.00	∞
Mismatch Loss dB	0.00 dB	0.04 dB	0.10 dB	0.18 dB	0.28 dB	0.41 dB	0.57 dB	0.76 dB	0.98 dB	1.25 dB	1.56 dB	1.94 dB	2.38 dB	2.92 dB	3.59 dB	4.44 dB	5.57 dB	7.21 dB	10.11 dB	∞ dB

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[abcd567]

ANOTHER EXPERIMENTAL DESIGN - 6 ELEMENT COILED DIPOLE.
FITS INSIDE 25mm PVC PIPE

NOT BUILT & TESTED YET

Gain = 8.5 dB in horizontal direction, SWR = 1.65

SEE BELOW SCREENSHOTS OF COMPUTER SIMULATION USING 4NEC2 SOFTWARE
(available free of cost at http://www.qsl.net/4nec2/):


SIMULATION OUTPUT: ANTENNA LAYOUT, SWR, GAIN, & PATTERN
6 section-coiled-dipole-output.jpg

INPUT: DIMENSIONAL DATA OF ANTENNA, FREQUENCY, CABLE IMPEDANCE, CABLE CONNECTION POINT
6 section-coiled-dipole-input.jpg

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[trigger]

Hi ab cd,
That one looks interesting. I have a bit of wire left so I'll have a go at building it and I'll report back.

I've tried the coiled whip you posted above but had not much success with or without the ground plane. The Franklin is much better.

Do you know how well theory translates into practise or do you have to build something to try it out?

[abcd567]

Hi ab cd,
That one looks interesting. I have a bit of wire left so I'll have a go at building it and I'll report back.

I've tried the coiled whip you posted above but had not much success with or without the ground plane. The Franklin is much better.

Do you know how well theory translates into practise or do you have to build something to try it out?

Theory gives fairly accurate results. When the antenna is built, it is never exactly as in theory (i.e. wires not perfect straight lines, wires not perfectly vertical/horizontal, coil not a perfect circle or perfect helix, wire dia & lengths not very accurate etc), so the results may be substantially different. Best is to build-try-trim/adjust-try.

Sent from my N762 using Tapatalk 2

[abcd567]

ANOTHER EXPERIMENTAL DESIGN - 5/8 WAVELENGTH DIPOLE WITH TUNING/IMPEDANCE MATCHING COIL.
FITS INSIDE 25mm PVC PIPE

NOT BUILT & TESTED YET

REVISED ON APRIL 03, 2014 DUE TO ERROR IN EARLIER INPUT/OUTPUT DATA

Gain = 5.81 dBi, SWR = 1.37

SEE BELOW SCREENSHOTS OF COMPUTER SIMULATION USING 4NEC2 SOFTWARE
(available free of cost at http://www.qsl.net/4nec2/):


SIMULATION OUTPUT: ANTENNA LAYOUT, SWR, GAIN, & PATTERN
dipole+coil-output-R1.png

INPUT: DIMENSIONAL DATA OF ANTENNA, FREQUENCY, CABLE IMPEDANCE, CABLE CONNECTION POINT
dipole+coil-input-R1.jpg

COIL & FEED DETAILS
dipole-coil-details-R1.png

[SpaxmoidJAm]

i managed to have a quick play at lunchtime with sprectrum analyser today, i thibk after getting my coupler the right way round i got some readings, the quick and dirty bent bit of wire wedged in a tnc connector did have a resonance near 1090MHz 3 db's or so but the good resonance was down at 860MHz 12 db's.

Tried to use the network analyser but was got confused by its calibration procedure and ran out of time, once i'm happy and i sort of know what i'm doing i'll get some screen grabs of stuff.

[abcd567]

i managed to have a quick play at lunchtime with sprectrum analyser today, i thibk after getting my coupler the right way round i got some readings, the quick and dirty bent bit of wire wedged in a tnc connector did have a resonance near 1090MHz 3 db's or so but the good resonance was down at 860MHz 12 db's.

Tried to use the network analyser but was got confused by its calibration procedure and ran out of time, once i'm happy and i sort of know what i'm doing i'll get some screen grabs of stuff.

Good! Keep it up. We all will benefit from your work

Sent from my N762 using Tapatalk 2

[charan]

please post how to make a resonator coil; turns, diameter etc

[Oblivian]

please post how to make a resonator coil; turns, diameter etc

Did you not click the images? they are there.

Length required to make turns can be made with antenna 5/8 calculators. Which at 1090mhz is 160mm

If they are 1/4 wave coils. The standard length is 56mm

[SpaxmoidJAm]

I worked out where i was going wrong with the network analyzer and made a quick aerial this lunchtime, in fact i made the top half of this aerial with four 138mm radial arms for the ground plane


6 section-coiled-dipole-output.jpg
This was the output
test2.jpg

although the notch at 1090MHz isnt as big as the one around 860 its got reasonable bandwidth.

[abcd567]

I worked out where i was going wrong with the network analyzer and made a quick aerial this lunchtime, in fact i made the top half of this aerial with four 138mm radial arms for the ground plane


[ATTACH=CONFIG]3760[/ATTACH]
This was the output
[ATTACH=CONFIG]3806[/ATTACH]

although the notch at 1090MHz isnt as big as the one around 860 its got reasonable bandwidth.

Try to trim the limb lengths slightly. This may improve 1090 MHz notch.

[abcd567]

I worked out where i was going wrong with the network analyzer and made a quick aerial this lunchtime, in fact i made the top half of this aerial with four 138mm radial arms for the ground plane


[ATTACH=CONFIG]3760[/ATTACH]
This was the output
[ATTACH=CONFIG]3806[/ATTACH]

although the notch at 1090MHz isnt as big as the one around 860 its got reasonable bandwidth.

Try also (1) bend downwards the earth plane wires, so that their tips are say about 40 to 50 mm below horizontal (2) use a little longer earth plae wires say 150 mm instead of 138mm

Sent from my N762 using Tapatalk 2

[abcd567]

VELOCITY FACTOR OF COAXIAL CABLES:

The velocity factor VF of a medium is ratio of velocities of propagation of Electromagnetic waves in that medium (v) and in vacuum (c).

The velocity of propagation of Electromagnetic waves in a medium depends on:
(1) Medium's electrical characteristic relative permittivity er.png (dielectric constant)
(2) Medium's magnetic characteristic relative permeability ur.png (which is the measure of the ability of a material to support the formation of a magnetic field within itself).

VF4a.png

Velocity Factor
VF4b.png

Values of Relative permeability ur.png
Relative permeability is usually 1 for non-magnetic materials such as cable insulation materials.

Values of Relative permittivity er.png

• Vacuum = 1 (by definition)
• Air = 1.00058986
• PTFE/Teflon = 2.1
• Polyethylene = 2.25
• Foamed Polyethylene = 1.75 to 1.35
  (foamed polyethylene is a mixture of gas and polyethylene and it's electrical parameters depend on solid to gas proportion)

Hence Velocity Factors (VF) are calculated as follows:

• For PTFE/Teflon insulated coax, VF = 1 / √(2.1 x 1) = 0.69
• For Polyethylene insulated coax, VF = 1 / √(2.25 x 1) = 0.66
• For foamed polyethylene insulated coax, the VF ranges between VF = 1 / √(1.75 x 1) = 0.76 & VF = 1 / √(1.35 x 1) = 0.85

**Information below is quoted from Coaxial Cable Manufacturer Belden's Catalouge:
DIELECTRIC CONSTANT
• Symbol: er.png
• Very important for electronic cables
• Lower er.png = Lower capacitance, Higher impedance, Lower attenuation.
• Air is best dielectric (er.png = 1)
• Adding air to (foaming) any material lowers its dielectric constant er.png.

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[SpaxmoidJAm]

Try also (1) bend downwards the earth plane wires, so that their tips are say about 40 to 50 mm below horizontal (2) use a little longer earth plae wires say 150 mm instead of 138mm

Sent from my N762 using Tapatalk 2

That has improved the notch, but I think the inherent problem with this design is that you cannot adjust the other two lengths of the antenna. Making it not the best design to go for if your making your first antenna. That being said 5.5 to 6 db's isn't to bad.

test3.jpg

what I might try is coupling each stage with a connector so it can be adjusted but again anyone without equipment would be working blind.

Think a collinear is next to try.

here's the aerial
WP_20140404_001.jpg