ADS-B antennas
Nextech magnetic mount whip antennas
nextech make magnetic mount antennas with 2 metres of coax with and SMA male connector that seems to work reasonaly OK at 1090 MHz
Here are the parameters of the 4G 700MHz antenna before tuning:
The parameters after tuning and deployed at YSWG:
Turning was performed by capacitively loading the coil with wire wrap run around the turns on one side of the coil.
Jaycar lists various nextech antennas for mobile phone usage,
- 5dBi https://www.jaycar.com.au/nextech-5dbi-magnetic-mount-4g-antenna/p/AR3340
- 7dBi https://www.jaycar.com.au/nextech-7dbi-magnetic-mount-4g-5g-antenna/p/AR3344
Both these antennas work better than the shorter antenna supplied by Core Electronics and PiHut
colinear
The Wheeler version of COCO found its way into commercial production in the 460-MHz range.
The antenna used a dielectric housing for support of the somewhat floppy coaxial cable and for weather protection. To place the antenna at DC ground relative to its mounting location, the top section used a short between the inner and outer conductors at the ¼-λ mark, although the section continues for the full section length.
Along the base section, also a full electrical half-wavelength, the makers installed three ¼-λ rods connected to the coaxial cable braid 1/4-λ from the bottom of that section. However, section continues below the rods for its full length.
The feedpoint — close to 50 Ω in the antenna described in the article — is at the base of the lowest section.
Measurements
coax loss
velocity factor
- https://www.jackenhack.com/diy-coaxial-collinear-antenna-ads-b-sdr-receiver-measuring-cable/
- https://owenduffy.net/blog/?p=18245
- via CH0 and CH1 phase shift or via TDR on CH0 https://www.youtube.com/watch?v=aWvPB299U60
ferrites
Ferrite supression can be tested with a nanoVNA. Very interesting.
common mode choke
Filter loss
Coax
The antenna may be made with any reasonable coax, including the relatively lossy RG58 at 1090MHz, however the feedline should use low loss coax like LMR-100
bibliography
- https://forum.planefinder.net/threads/1-4-wave-ground-plane.156/
- https://apps.dtic.mil/sti/tr/pdf/ADA101340.pdf
- https://forum.planefinder.net/threads/very-small-collinear-antenna-300-mm.177/
- https://www.qsl.net/py4zbz/adsb.htm
- https://martybugs.net/wireless/collinear.cgi
- https://discussions.flightaware.com/t/has-anyone-simulated-tried-a-wire-colinear-with-two-single-loops/70422/10
- https://discussions.flightaware.com/t/coaxial-collinear-coco-antenna-hyps-facts/17274
- https://discussions.flightaware.com/t/coco-coaxial-collinear-antenna-tips-tricks/69144/32
- coaxial https://www.arrl.org/files/file/QST/This%20Month%20in%20QST/January%202014/VirtualRadarJan2013QST.pdf
^ https://ham.stackexchange.com/questions/17014/440mhz-collinear-dipole-array-suitable-coax
^ https://ham.stackexchange.com/questions/7076/how-the-coaxial-collinear-antenna-works
- https://www.repeater-builder.com/antenna/pdf/build-a-9dB-70cm-collinear-antenna-from-coax.pdf
- http://sm0vpo.altervista.org/antennas/7db-colinear.htm
- 'quarter wave coco https://vu3dxr.in/building-a-quarter-wavelength-coaxial-collinear-antenna-for-2-meters/
- https://discussions.flightaware.com/t/coaxial-collinear-coco-antenna-hyps-facts/17274/20
- 1/2 wave co co https://k7zgq.blogspot.com/2012/12/coax-cable-collinear-wireless-and-or.html
- 1/4 wave co co https://www.srgclub.org/CollinearAnt-HomeBrew.html