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:
- ¼ wave 45deg 6 leg spider
- ¼ wave “Lynx” 52mm canttena
- ¼ wave 90deg mini 32mm ground plane
- ¼ wave Maxi 98mm cantenna
- ¼ wave 45deg 16 leg spider – radial 69mm from 45 deg bend to tip
- ¼ wave 45deg 16 leg spider – radial 69mm from centre to tip
- 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.