Antenna Testing, Home Built , ¼ waves


#1

Introduction
1/4 waves and J-Poles are probably the easiest antennae to make at home, well thats what I found and here are some results…

Aim:
Before installing the Flight Aware Rx on the outside of my home I wanted to check which type of antenna gave the best reception. All tests were performed with the Rx in the same location and the data for each test was collected over 24 hour period, using both the Mode S Mixer data capture application and the Flight Aware flight counters.
I would ideally like more gain than a ¼ wave (no gain) but I have a small 78m hill one mile (2020m) to the east of me. So the two antenna types I selected to for testing where ¼ waves and J-poles. Both have relatively high take-off elevations, so the effect of the hill will be minimised. A Colinear would have too flat a radiation pattern for my location and they have more variables in their construction, thus without test equipment, the performance of a colinear would be a shot in the dark (for me at least).

Test Equipment:
Rx: Noolec SMArt, Aluminum Enclosure, 0.5PPM, SMA connector (2017)
Filter: 1090Mhz surface mount, 50 Ohm, SMA connector Passband: 1086 ~ 1094 MHz
Processor: Raspberry Pi 3
Operating Sys: PiAware 3.5.3 with Mode S Mixer
USB cable: Lindy 100mm from Rx to the processor
Arial main cable: 1000mm double screened satellite cable, 75 Ohm
Arial pig tail: Lindy 100mm coax, SMA to F type panel mount
Arial connector: F Type 75 Ohm
Datacomms: Pi Ethernet to the power line (Pi WiFi disabled) .
Location: Inside concrete block built garage, tile roof, aerial 2m above floor
Ground 97.5m Above sea level
Note: There is only one impedance step change in the Rx line 75 Ohm to 50Ohm, which occurs at the join between the satellite cable the pigtail. Not a significant issue as the rig is not a transmitter.
Date:
From 20 February 2018 to

Tests ¼ wave:

  1. ¼ wave 45deg 6 leg spider
  2. ¼ wave “Lynx” 52mm canttena
  3. ¼ wave 90deg mini 32mm ground plane
  4. ¼ wave Maxi 98mm cantenna
  5. ¼ wave 45deg 16 leg spider – radial 69mm from 45 deg bend to tip
  6. ¼ wave 45deg 16 leg spider – radial 69mm from centre to tip
  7. ¼ wave Coke Can Cantenna

The test location was the same for all tests The location is not ideal thus the results of one antenna should only be compared to results of another antenna in this test.

The test location was a block build garage situated within a brick built housing estate.

Test 1:
¼ wave 45deg 6 leg spider /
garage /
20-23/02/2018 /
Tuesday 20:00-Friday 20:00

Arial element length: 69mm x 1.5mm copper
Connector: F Type

Comments:
Easy to connect the antenna to the cable as access is only slightly restricted by the radials.
Arial element is protected by the tube of a plastic ball point pen.
Plastic ballpen used to protect vertical element.
Good range.
Easy to construct (soldering iron required).
Waterproof F connector with silicon sealant
Very low visual impact


Average daily flights : 1,502
SD of daily flights : 94.26

Test 2:
¼ wave “Lynx” 52mm canttena /
garage /
24-27/02/2018 /
Saturday 15:00 – Tuesday 20:00

Arial element length: 69mm x 1.5mm copper
Can height: 69mm
Can diameter: 52mm
Connector: F Type

Comments:
Difficult to tighten the F connector on the cable to the antenna due to the sides of the can being too close to the connector.
Fair range
Very easy and quick to construct
Low visual impact


Average daily flights : 1,556
SD of daily flights : 64.347

Test 3:
Just to see what happens if you remove the sides of the can.
¼ wave 90deg mini ground plane /
garage /
27/02/2018 – 02/03/2018 /
Tuesday 22:00 – Friday 20:00

Arial element length: 69mm x 1.6mm copper wire
Can height: 0mm
Can diameter: 32mm
Connector: F Type

Comments:
Shows you need a ground plane.
Poor range
Very easy and quick to construct
Low visual impact


Average daily flights : 955
SD of daily flights : 29.698

Test 4:
¼ wave Maxi 98mm cantenna /
garage /
02/03/2018 – 06/03/2018 /
Friday 22:00 – Tue 23:00

Arial element length: 69mm x 1mm brass rod
Can height: 69mm
Can diameter: 98mm
Connector: F Type

Comments:
Good access to F connector.
Good range
Very easy and quick to construct
Higher visual impact


Average daily flights : 1,365
SD of daily flights : 38.039

Test 5:
¼ wave 45deg 16 leg spider /
garage /
7-11/03/2018 /
Wed 23:00- Sunday 13:00

Radial legth: 70mm on the 45 slope and 14mm horizontal
Arial element length: 69mm x 1mm brass rod
Connector: F Type

Comments:
Easy to connect the antenna to the cable1mm brass as access is only slightly restricted by the radials.
Good range.
Easy but slow to construct (soldering iron required).
Very low visual impact
Need to work out where to measure the radial length from as this design is not as food as the 6 leg spider or swap the element for a 1.5mm copper wire


Average daily flights : 1,636
SD of daily flights: 31.512

Test 6:
Just to see where you should measure the radial length from.
¼ wave 45deg 16 leg spider /
garage /
11-13/03/2018 /
Sunday 13:00-Tues 20:00

Arial element length: 69mm x 1mm brass rod
Radial: 1mm brass wire
Radial legth: 69mm FROM Centre to Radial Tip
Connector: F Type

Comments:
Easy to connect the antenna to the cable as access is only slightly restricted by the radials.
Good range.
Easy but slow to construct (soldering iron required).
Very low visual impact

**Similar to the test 5 but radials cut to measure 69mm from arial element to radial tip. **
Performance was BETTER when the radial length was measured from the 45 deg bend.

Test 7:
¼ wave Coke Cantenna /
garage /
13-16/03/2018 /
Tues 20:00 – Friday 20:00

Arial element length: 69mm x 1mm brass rod
Diameter: it’s a coke can
Height: 69mm
Connector: F Type

Comments: Good but looks like the 6 leg spider is a little better than a cantenna. Looks like the diameter of a cantenna needs to between coke can and 52mm

Results:
From the results above the 6 leg 45 deg 1/4L antenna performed as well or very slightly better than the “Lynx” 52mm cantenna. The cantenna was found to be the easiest to construct of all the antenna.

Below is a Flight Aware timeline which can be used to compare the performance of each antanna as the date of each test was recored and show above.



Antenna Testing, Home Built super J pole or ¼ wave?
Antenna Testing, Home Built, simple J-Poles
#2

@g7pnu
Great! Happy experimenting. DIY is fun, gives lot of satisfaction and pleasure

:+1: :clap: :+1:


#3

Thank you for your post @abcd567 “How To Get VRS-Like Coverage Map on RPi” without it I couldn’t have made any useful measurements. Do you know of any other applications I can run on a Pi (or Linux PC) to measure the efficiency of a given antenna?


#4

Install “Web Portal” using the method given in the following thread. The Web Portal has lot of performance graphs which are helpful in evaluating you antenna.

ADS-B Receiver Project Setup Scripts

It will offer you options to update (actually it is upgrade, takes a lot if time, I always say no to it), then to install dump1090-mutability/dump1090-fa, data feeders etc. Say NO to all. At the end it will present option for Web Portal. Say OK to it. Then it will ask advance option say NO to it, and then installation will start.


#5

Looks like fun @g7pnu. I too have tried many home built antennas for tracking ADS-B on1090, 978 and AIS around 161MHz. I got into using the pi’s within the last year and have been having a ball with cantenna’s, spiders and a j-pole for the AIS tracking. Haven’t tried J-poles or Slim Jims for ADS-B yet so I look forward to your results. I think a lot of us do this for the fun factor and that’s what it’s all about.


#6

Thank you @Dunnsville. I’m cutting the legs of my little J Pole 1mm each evening and looking at the timeline it’s going to take me 11 days to get 198mm * 66mm, which may be the optimum length. Got to test and measure. :slight_smile:


#7

Thank you @abcd567 I will try your recommendation after I have completed my current set of J pole tests. Have a good evening.