Please scroll down to see the test result graphs at the bottom.
(1) The three antennas under test were:
(a) Coiled Whip
(b) Stock Whip
(c) Optimized Whip
(2) In order to minimize number of variables, only the removable parts of Whips were interchanged. All other hardware, location, and software/gain settings were identical. Even the same mag mount base & RG174 coax cable was used for all the three whips.
(3) In order to be sure that results are not influenced due to fluctuation in traffic, test were conducted twice.
(a) First test between 2pm & 3 pm
(b) Repeat test between 4pm & 5pm
The can I used in above experiment as ground plane, has 100mm (4 inches) dia.
I am planning a second round of tests.
Keeping same whip, I will try cans of larger & smaller dia: mag mount only which has 25 mm (1 inch) dia, cans of dia 50mm (2 inches), 75mm (3 inches), 100mm (4 inches) and 300 mm (12 inches).
The antenna length is measured from the point the core wire of coax connects to it. That point is hidden inside the base and is 15 mm below the point where whip screws into the base, and is continuation of the brass screw. Hence the actual length of antenna is 15+52=67mm. Please see diagram below.
I did not download and burn Piaware image on my microSD card. Instead I downloaded and burned “Raspbian Jessie Lite” from raspberrypi.org/downloads.
After burning the Raspbian Jessie image to my microSD card, I used an automated method (linked below) to install dump1090, 4 data feeders (flightaware, planefinder, flightradar24, and adsbexchange) and rrd graphs (web portal) which gives me the graphs you have seen.
The automated installation method I have used after burning Raspbian Jessie image, is given in the FIRST Post of this thread:
Note: During installation of Web Portal, I did NOT choose Advanced option (MySQL and MySQL Lite) as it will quickly fill storage on my 8Gb microSD card by storing flight data continously. This does not affect creation & display of graphs.