PCB ADS-B 1090MHz Antenna

#21
Thanks for posting results of VRS range plot.

Comparing the range plot of pcb with 1/4 w gp, both are almost identical.

This is with both the antennas indoor. It will be interesting to see how the two antennas compare when both installed outdoor.
Hi All,

An interesting comparison which proves antenna theory is alive and well <grin>.

I'd expect the PCB antenna and a 1/4 wave ground plane to have the same performance because one is a variation of the other. The PCB antenna is a centre-fed 1/2 wavelength dipole (with the method of feeding it resembling a flattened form of coaxial dipole), which has the same radiation pattern and gain as the ground plane. The PCB antenna certainly lends itself well to being mounted in a radome for weather-proofing, resulting in a cheap, low profile and low weight antenna.

FWIW, some PVC pipe is not transparent to RF, and can be very lossy. A quick test is to place a short length of the pipe in a microwave oven, along with glass of water, and run the oven for 30-60 seconds. If the PVC stays cool it's a satisfactory material for the radome. If it gets warm or hot, don't use it with the antenna because it's lossy and absorbs microwave energy (including ADS-B).
 

ab cd

Senior Member
#22
Hi All,

An interesting comparison which proves antenna theory is alive and well <grin>.

I'd expect the PCB antenna and a 1/4 wave ground plane to have the same performance because one is a variation of the other. The PCB antenna is a centre-fed 1/2 wavelength dipole (with the method of feeding it resembling a flattened form of coaxial dipole), which has the same radiation pattern and gain as the ground plane. The PCB antenna certainly lends itself well to being mounted in a radome for weather-proofing, resulting in a cheap, low profile and low weight antenna.

FWIW, some PVC pipe is not transparent to RF, and can be very lossy. A quick test is to place a short length of the pipe in a microwave oven, along with glass of water, and run the oven for 30-60 seconds. If the PVC stays cool it's a satisfactory material for the radome. If it gets warm or hot, don't use it with the antenna because it's lossy and absorbs microwave energy (including ADS-B).
Your views match exactly with my views. Are we telepathic? :D

2018-05-16 17.59.19.jpg

.

Die Koaxialantenne.png
 
#23
Telepathic will do nicely! :)

I should comment on the only significant difference (more relevant in theory than in practice) between the two antennas which is that the Zo (impedance) of the GP (with horizontal radials) is about 35 ohms whereas the coaxial dipole is nominally 75 ohms, or probably a bit less due to the elements' large diameter relative to their length. The pic is a coaxial dipole I made a few years back as a reference antenna for ADS-B. It's not weatherproof in the format shown but it might give home constructors some brain fodder. The "support" tube is 10mm aluminium which acts as the outer conductor for the RG-213 inner conductor that sticks out the top as the radiating element. The outer braid on the coax has been removed. Holding the Berocca tube concentric is an aluminium disc tapped to match a thread on the end of the end of the aluminium tube (3/8" 24 TPI from memory). The end of the Berocca tube is pop riveted to that disc in three places.


ADSB Coaxial Dipole_01.jpg
 
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