antenna help
- Thread starter c0by
- Start date
ab cd
Senior Member
Soldering or no soldering, tape or just air gap in between pieces....whatever method of construction you use, the result is same - very few lucky DIY CoCo makers get the claimed or expected performance.
All Collinears (CoCo, Coiled Whips, Franklin etc) are very alluring because these are very simple to make. The problem shows up only when these are put to service. The reason is these are very sensetive to dimensions & insulation characteristics. A few mm error in design or construction can knock down these from "excellent" to "poor" category.
The collinears are successful only when these can be tested & trimmed/tweaked using costly test equipment, so costly that these are generally beyond the reach of common hobbyist.
The easiest antennas for DIY are those having a vertically upward pointing whip with length equal to 1/4 wavelength (69mm for ADS-B), connected to core of feeding coax, PLUS a "support structure" connected to shield of the feeding coax. This type of antenna is naturally resonant, naturally impedance matched to the 75 ohm / 50 ohm system, and has good dimensional tolerance, one or two mm error in whip & support structure dimensions will not result in appreciable/noticeable loss of performance. These do not require any test equipment or trimming/tweaking.
The only disadvantage of these simple & easy antennas is low gain (1.5 to 2 dBi). This can be overcome by adding an in-Line Amplifier.
The "support structure", connected to shield of feeding coax cable, comes in various forms, some are listed below:
(1) A vertically downward whip, 1/4 wavelength (69mm) - the 1/2 wavelength Dipole
(2) Horizontal or slanting radials (3, 4, 6 or 8) - Spider
(3) Horizontal metallic disk - Platetenna
(4) Metallic food or beverage Can - Cantenna
http://forum.planefinder.net/threads/three-easy-antennas-for-beginners.248/
.
All Collinears (CoCo, Coiled Whips, Franklin etc) are very alluring because these are very simple to make. The problem shows up only when these are put to service. The reason is these are very sensetive to dimensions & insulation characteristics. A few mm error in design or construction can knock down these from "excellent" to "poor" category.
The collinears are successful only when these can be tested & trimmed/tweaked using costly test equipment, so costly that these are generally beyond the reach of common hobbyist.
The easiest antennas for DIY are those having a vertically upward pointing whip with length equal to 1/4 wavelength (69mm for ADS-B), connected to core of feeding coax, PLUS a "support structure" connected to shield of the feeding coax. This type of antenna is naturally resonant, naturally impedance matched to the 75 ohm / 50 ohm system, and has good dimensional tolerance, one or two mm error in whip & support structure dimensions will not result in appreciable/noticeable loss of performance. These do not require any test equipment or trimming/tweaking.
The only disadvantage of these simple & easy antennas is low gain (1.5 to 2 dBi). This can be overcome by adding an in-Line Amplifier.
The "support structure", connected to shield of feeding coax cable, comes in various forms, some are listed below:
(1) A vertically downward whip, 1/4 wavelength (69mm) - the 1/2 wavelength Dipole
(2) Horizontal or slanting radials (3, 4, 6 or 8) - Spider
(3) Horizontal metallic disk - Platetenna
(4) Metallic food or beverage Can - Cantenna
http://forum.planefinder.net/threads/three-easy-antennas-for-beginners.248/
.
Last edited:
