Antenna Ground Plane

[abcd567]

@geckoVN

Does that describe you when you built your first coco?

No, and all my attempts to make high gain colinears (coax & wire) have failed, and that is how I learned what I have said in my last post.

.

@abcd567

AVAILABLE ANTENNA DESIGNS
There are a lot of antenna designs available which meet above criteria.
However almost all high gain antennas sch as Coaxial Collinear, Wire Collinear with Coils, Wire Collinears with stubs, Stripline antennas etc, require following to give good performance:

1. High accuracy of dimensions.
2. Have impedance mismatch with receiver / have high SWR, and require additional components to bring down SWR
3. Require test equipment and technical know-how to tune to designed frequency, and to reduce SWR to 1.5 or less

Obviously, these are unsuitable for DIY antenna making by a normal ADS-B hobbyist, who does not have any test equipment and any technical know-how.

ANTENNA DESIGNS SUITABLE FOR A NORMAL HOBBYIST
The only antennas which are (1) reasonably tolerant to dimensional errors and (2) have impedance in range 75 to 50 ohms (SWR 1.5 or less) are listed below. These are therefore suitable for making a DIY antenna by an average hobbyist without any test equipment and without any technical know-how.

1. The 1/2 wavelength dipole (2 limbs, each 1/4 wavelength)
2. The 1/4 wavelength monopole with ground plane (Spider & Cantenna)
3. The stock whip mag-mount antenna (supplied with DVB-T dongle), cut to size and placed on a metal object such as a food can.

These easy antennas have one disadvantage. These have low gain (1.5 to 2 dBi).
If used with very short runs of coax, these perform ok. With long runs of Coax, these require amplifier. With introduction of FlightAware ProStick and ProStickPlus with integral RF-preamplifier, this deficiency is overcome. Even if a generic DVB-T (black/blue) is used, adding a satellite amplifier or a custom made LNA covers the low gain deficiency of 1/4 wavelength groundplanes.

COMMERCIAL ANTENNAS
If a hobbyist is not interested in fun and satisfaction of making a DIY antenna, and is simply interested in best performance, he can purchase a commercial antenna such as Flightaware 26 inch antenna (Gain 5.5 dBi, SWR<1.5), or high gain antennas by other manufacturers, available at ebay/amazon/respective sites.

For FlightAware antenna:
https://www.amazon.com/dp/B00WZL6WPO