ADS-B antennas

From regional-training

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 wound around across the turns on one side of the coil. (An alternative tuning method would be to slide a section of tubing up and down over the coil turns.)

Jaycar lists various nextech antennas for mobile phone usage,

Both these antennas work better than the shorter antenna supplied by Core Electronics and PiHut

colinear

1/2 wave co co with balun
quarter wave co co with air balun

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.

wheeler co co

Measurements

coax loss

velocity factor

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-400 or RG-218 - do not use RG58.

coax parameters

Coax LMR-600 RG-8X EcoFlex 10 Belden 9913
RG8/U		 LMR-400 * RG-11 Westflex 103 RG-218 * LMR-300 LMR-240 RG-213 RG-6 RG-142 RG-400 RG-58 RG-316
Inner solid BCCAI SC stranded C solid BC S BC BC SC SC SBC Solid BC SC S C Copper Silver stranded TC
Dielectric foam PE foam PE low loss PE PE foam PE foam PE PE air PE PE foam foam PE PE foam PE PTFE PE
Outer Outer tape and tinned copper AL tape tinned braid Copper tape copper braid Tri-laminate AL and braid Tinned Copper CCS CCS Copper Braid Al tape tinned C braid Al tape and tinned copper copper Al tape Copper braid Silver platted Copper Braid Tinned Copper braid
dia centre 4.47 2.74 2.85 2.7432 2.74 ? 2.62 4.95 1.78 1.42 2.29 0.74 0.93 ? ? ?
dimens dielectric 11.96 7.24 7.25 7.24 7.39 7.2 17.27 4.83 3.81 7.24 4.7 2.95 ? ? ?
Outer 12.45 8.13 < 10.2 8.13 8.13 9 5.72 4.52 7.98 6.3 3.96
V.F. 0.85 0.85 0.84 0.84 0.84 0.81 0.66 0.85 0.83 0.66 0.66 0.7 0.695 0.659 0.69
Impedance 50 50 50 50 50 75 50 50 50 50 50 75 50 50 50 50
Loss 100 MHz
per 100’ 		0.8 1.5 1.22 1.4 1.4 1.46 1.40 1 2.1 2.1 2.1 2.9 3.9 4.4 4.9 11
Loss 1000 MHz
per 100' 		2.6 3.9 4.33 4.4 4 5.85 5.12 5 7.3 7.6 8 11 12.9 14.7 20 38

bibliography

^ https://ham.stackexchange.com/questions/17014/440mhz-collinear-dipole-array-suitable-coax

^ https://ham.stackexchange.com/questions/7076/how-the-coaxial-collinear-antenna-works

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