ADS-B DIY Antenna

[ab cd]

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DIPOLE LENGTH vs. RADIATION PATTERN & GAIN

As seen from above diagram, the full wavelength dipole has a combination of high gain and a horizontal pattern which is most favourable for ADS-B, but has the disadvantage of very high impedance, which requires impedance matching arrangement (stub, coil etc)

The 1.25 wavelength dipole is also similar to full wavelength, and has slightly better directivity in horizontal direction, & lower impedance than fullwave, hence easier to match the impedance. It Is very popular as 5/8 wavelength whip with ground plane (the 1.25 wavelength dipole is two limbs of 5/8 = 2 x 5/8 = 10/8 =1.25).

The 5/8 wavelength whip with maching coil at bottom is a popular whip for mounting on vehicles, where metallic body of the vehicle serves as ground plane.

 

[Richard Lee]

In the fine print, (bottom line) it says the PY4ZBZ Full-Wave 1090 has good gain, because of it's height above ground.
The radiation pattern shown here, looks nothing like the free-space Lazy 8 full-wave pattern shown in your post.

From what I can tell, even when the antenna is radiating a symmetrical pattern, the ground has an effect.
The sweet spot of good performance depends on pattern shape, wave-length and height above ground.

Tracking planes over NYC, north over the Canadian border, and into northeastern Maine, seems to show this antenna is working better than the 9dBi DPD.
The tower is effecting my pattern. (They always do). But, it's impossible to say in what direction the losses and gains occur.

 

[ab cd]

In the fine print, (bottom line) it says the PY4ZBZ Full-Wave 1090 has good gain, because of it's height above ground.
The radiation pattern shown here, looks nothing like the free-space Lazy 8 full-wave pattern shown in your post.

From what I can tell, even when the antenna is radiating a symmetrical pattern, the ground has an effect.
The sweet spot of good performance depends on pattern shape, wave-length and height above ground.

Tracking planes over NYC, north over the Canadian border, and into northeastern Maine, seems to show this antenna is working better than the 9dBi DPD.
The tower is effecting my pattern. (They always do). But, it's impossible to say in what direction the losses and gains occur.

At 1090 MHz:
full wavelength dipole has two limbs, each limb = 275/2 =138 mm
1.25 wavelength dipole ( 2 x 5/8) has two limbs, each limb = 275 x 1.25/2 (or 275 x 5/8) = 172mm

The PY4ZBZ Dipole is 150mm each limb.
It is neither a fullwave dipole nor a 1.25 wavelength ( 2 x 5/8 wavelength) dipole. It is something in-between the two.

If you compare the upper half of lazy 8 of 1.25 wavelength dipole, it is very similar to pattern of PY4ZBZ dipole: Two main horizontal lobes towards left & right, and two small upward lobes n the middle. Considering ground instead of free space has logically chopped-off the lower half of the lazy 8, as there is no signal arriving from below the ground.

 

[ab cd]

Following are some details from an antenna manufacturer for CB (27 MHz) antennas, but serve a good example of popularity of 5/8 wavelength on Dipoles.

image 1 of 2 - Screenshot from part of manufacturer's web page

Image 2 of 2 - Radiation pattern of some of above antennas - These look similar to pattern for PY4ZBZ dipole

 

[ab cd]

THE COILED DIPOLE + AMPLIFIER TRIAL RUN

Amplifier : Location = Near Antenna; Gain = 13-18 dB

Cable (between antenna & Receiver): Length = 50 ft/15 m; Type = Coaxial RG6, cheap quality.

Duration of trial run = 2 hrs, on evening of 06 Sept 2014


Image 1 of 3 - Photo of the antenna & Amplifier

Image 2 of 3 - The VRS Range Plot - 2 hrs trial run

Image 3 of 3 - The Range Plot on adsbScope - 2 hrs trial run

 

[ab cd]

I have posted a photo of coiled antenna in my last post. The coils are 65mm long x 6.4mm dia, about the size of a finger. Now see below the photo of another antenna coil:

Enormous antenna loading coil used in a powerful longwave (30-300 kHz) radiotelegraphy transmitter in New Jersey in 1912.

 

[ab cd]

CRITICAL DEPENDENCE OF ANTENNA TUNING/SWR ON COIL DIMENSIONS
I was modelling a 4-element dipole with single-turn coil. I used two options
(1) for countries using Imperial/US system: use 3/4 inch dia PVC pipe as former to wind the coil.
(1) for countries using metric system: use 25mm dia PVC pipe as former to wind the coil.

The 3/4 inch PVC pipe has outer dia = 1.05 inch = 26.7mm
The 25mm PVC pipe has outer dia = 25mm
The difference between two dimeters is about 6.5%. I did not expect any difference in design if any of the two coil inner diameters are used.
When I ran the simulation, the outer limbs for lowest SWR were:
(1) 192mm in case of 26.7mm dia coil (3/4 inch pipe as coil former)
(2) 206mm in case of 25mm dia coil (25mm pipe as coil former)

Above shows how the tuning of antenna and achieving low SWR is critically dependent on coil dimensions.

Please see the screenshots of two simulations below.

CASE 1 - Coil inner diameter = 26.7mm (Coil wound over 3/4 inch PVC Pipe)

=============================================================================================
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CASE 2 - Coil inner diameter = 25mm (Coil wound over 25mm PVC Pipe)

.

 

[ab cd]

Sleeved Dipole With Amplifier ..
Antenna+Amplifier assembly will fit inside 1-1/4 inch or 1-1/2 inch PVC Pipe for Outdoor Mounting

Amplifier Gain: 13-18 dB
Coax Cable between antenna & receiver: 50 ft/15 m RG6, Cheap Quality.

Step 1 of 3 - Design & Simulation

Step 2 of 3 - Construction

Step 3 of 3 - Trial Run 2 hrs

.

 

[ab cd]

In my last post above, I have used 3/4 inch copper water pipe, as the 1/2 inch & 3/4 inch sizes are most commonly available.
However, the antenna gain and coverage increases with increase in copper pipe diameter.
If larger size (1 inch or 1-1/4 inch or 1-1/2 inch) copper pipe is used, it will give better coverage, and the assembly will still fit inside a 1-1/2 or 2 inch PVC Pipe.

 

[ab cd]

Two types PVC pipe end caps, to protect antenna and amlifier inside the pipe, from rain water & moisture.

The #1 end cap seems better for both upper & lower ends of pipe, as it is glued to the pipe by a special adhesive for pvc pipes & couplings. Once glued, the lower endcap will not be dislodge by downward pull of coax or weight of antenna+amplifier assembly.

# 1

# 2

 

[ab cd]

Spider Antenna (146 MHz)

http://vk6ysf.com/146mhz_ground_plane_antenna.htm

Another Spider (435 MHz):
http://vk6ysf.com/435MHz_Ground_Plane_Antenna.htm

 

[Reg]

Aereo's array of antenna's is neat.

 

[plane-finder_user]

can you make more pictures and for what did you use that?
look very weird for me....

 

[ab cd]

This is an array of coin sized symetrical Inverted F Antennas (IFA). Each antenna unit is tuned to one on-air tv channel.

 

[ab cd]

Inverted-F antennas are widely used in cell phones, WLAN hardware, and other small wireless devices. The performance is similar to a quarter-wave ground plane.

The IFA is a monopole antenna, which is bent horizontally to reduce its height while still maintaining high radiation efficiency. A shunt stub is added to accomplish an impedance match.

[/B]

 

[plane-finder_user]

and you use that for adsb?

 

[ab cd]

and you use that for adsb?

No, I dont use it. Maybe forum member "Reg" (who originally posted photo of AeroAntena and started this discussion) has found a way to use it for adsb.

 

[Reg]

No, I dont use it. Maybe forum member "Reg" (who originally posted photo of AeroAntena and started this discussion) has found a way to use it for adsb.

Nope, not me. I was just replying to a post a few pages back. 'With all the antenna on the roofs, etc.. Thought that poster might be interested to see the Aereo's array.

btw, Thanks for sharing all your research ab cd.

 

[Turorit]

Just spent the evening reading this thread, great stuff!
I think I'll try out the pepsi antenna, half wave dipole & full wave PY4ZBZ Full-Wave.
I'm currently running a magmount 1090mhz included with the microADSB USB receiver I bought before the RTL stuff. It sits just on the edge of the tin roof & gets about 100km.
Also going to swap from my rtl e4000 dongle to the r820t & raise height of the antenna above the house on my tower

 

[ab cd]

Just spent the evening reading this thread, great stuff!
I think I'll try out the pepsi antenna, half wave dipole & full wave PY4ZBZ Full-Wave.
I'm currently running a magmount 1090mhz included with the microADSB USB receiver I bought before the RTL stuff. It sits just on the edge of the tin roof & gets about 100km.
Also going to swap from my rtl e4000 dongle to the r820t & raise height of the antenna above the house on my tower

After you have made and tried various antennas and have comparaed their performance, do one more project: add an inline amplifier.

The amplifier greatly enhances range of every antenna.

To make inline amplifier work, you will also need a dc power supply (dc adaptor) and power inserter,

The amplifier, dc power supply & dc inserter each will cost from $5 to $15 depending on make and the seller.