I need an antenna in the U-NII-4 spectrum. This means the signal is in the range of 5.850 GHz up to 5.925 GHz. The center frequency is 5.887 GHz. Let’s build an antenna for this frequency.

Co-linear antenna
Co-linear antenna

How do you know your antenna is tuned for the correct frequency? Good question! When making your own antenna you need to know a couple things:

Wavelength
The size of (elements of) an antenna is often related to the wavelength. For instance the elements of a 1/2 wave dipole antenna is half a wavelength in size. The wavelength is the distance a radiowave travels during one cycle.
The formula for the wavelength is:


\displaystyle \lambda = \frac{C}{f}

Where:
λ = wavelength (in meters or inches, we will be using the metric system below)
C = speed of light (299,792,458 meters per second in a vacuum)
f = frequency

[CP_CALCULATED_FIELDS id=”6″]

Velocity Factor
Now the speed of light is 299792458 meters per second. Now there is a catch, it is the speed in vacuum. When making an antenna, it is probably not constructed in a vacuum. When using a coax, the substance the wave travels through is the dielectrum insulator. This is the substance between the centre core and the metallic shield.

Image from Wikipedia
Coaxial cable

The Velocity Factor (VF) also called wave propagation speed or Velocity of Propagation (VoP) of a transmission speed is defined as follows: The ratio of the speed which a wavefront (i.e. radio signal) passes through the medium compared to the speed of light in a vacuum. The speed of a radio signal in vacuum is the same as the speed of light in a vacuum, which makes the Velocity Factor 1.0.

Impedance
Todo:

(V)SWR
When an antenna is tuned for sending you can assume it is also tuned for receiving. It would be nice to measure this. There is a device called Voltage Standing Wave Ratio meter often called SWR meter. This measures the impedance matching between the signal source and the antenna. When there is an impedance mismatch, this results in a standing wave along the transmission line. The ideal VSWR is 1:1. This optimum condition exists only when the load (antenna) has an identical impedance as the transmission line (Coaxial cable). Also the load should be free of inductance and/or capacitance. Good luck with that 😉 Any other situation results in voltage and current fluctuations along the transmission line.

Antenna types
Todo:

Next step
Now we handled the basic things we need to know we continue with the actual measuring of the performance of the antenna.
With the SWR meter we can determine the SWR value of a known frequency. When we measure different frequencies, we can make a plot which frequency gives the optimal SWR value. The measured points can be plot in a chart. This reveals the optimum frequency for the antenna. For this moment this is still my theory, but I will try to confirm this by actually doing it.

How do I get a signal source which is sending in the frequency domain I am interested in. It would be nice if the resolution is high to capture a proper curve.
The TS5823 has 200 mW transmit power and has 32 channels in the range 5645 Mhz till 5945 Mhz. The maximum frequency step is 22 Mhz so this is an ideal candidate to test a curve with.

Frequency Range 1 .. 4
Channel 1 .. 8

CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8
FR1 5865 5845 5825 5805 5785 5765 5745 5725
FR2 5733 5752 5771 5790 5809 5828 5847 5866
FR3 5705 5685 5665 5645 5885 5905 5925 5945
FR4 5740 5760 5780 5800 5820 5840 5860 5880

Looking at the frequencies it is possible to downsize the amount of channels where the frequency step is between 18 and 22 Mhz. This has a more consistent spread and it reduces the amount of channels to 16.

FR CH Frequency Spread   FR CH Frequency Spread
FR3 CH4 5645 n/a FR1 CH4 5805 20
FR3 CH3 5665 20 FR1 CH3 5825 20
FR3 CH2 5685 20 FR1 CH2 5845 20
FR3 CH1 5705 20 FR1 CH1 5865 20
FR1 CH8 5725 20 FR3 CH5 5885 20
FR1 CH7 5745 20 FR3 CH6 5905 20
FR1 CH6 5765 20 FR3 CH7 5925 20
FR1 CH5 5785 20 FR3 CH8 5945 20

Antenna segment connection
Antenna segment connection

Also a nice video is the following:
250 channel fpv receiver with spectrum analyzer which points to the fpv_receiver_module sourcecode on Github.

From Albion Alloys there is the following assortment which you can buy at Verspaget Modelbouw Eindhoven, Fredriklaan 104, Eindhoven:

Albion Alloys assortment
Albion Alloys assotment

Lengths are 305 mm.
The price level per category @ Verspaget (2016-02-10) is:
A: €5.80
B: €6.45
C: €7.00

Code Type a x b Piece(s)
A1 Brass Angle 1mm x 1mm 1
A2 Brass Angle 2mm x 2mm 1
A3 Brass Angle 3mm x 3mm 1
A4 Brass Angle 4mm x 4mm 1
A5 Brass Angle 5mm x 5mm 1
A6 Brass Angle 6mm x 6mm 1
Code Type a x b x c Piece(s)
CC1 Brass “C” Channel 1mm x 1.5mm x 1mm 1
CC2 Brass “C” Channel 1mm x 2.5mm x 1mm 1
CC3 Brass “C” Channel 1mm x 3mm x 1mm 1
Code Type a x b x c Piece(s)
UC1 Brass “U” Channel 1mm x 1mm x 1mm 1
UC2 Brass “U” Channel 1.5mm x 1.5mm x 1.5mm 1
UC3 Brass “U” Channel 2.5mm x 2.5mm x 2.5mm 1
UC4 Brass “U” Channel 4mm x 4mm x 4mm 1
Code Type Outer Dia x Wall x Inner Dia Piece(s)
AT1M Aluminium Tube 1mm x 0.25mm x 0.5mm 4
AT2M Aluminium Tube 2mm x 0.45mm x 1.1mm 4
AT3M Aluminium Tube 3mm x 0.45mm x 2.1mm 4
AT4M Aluminium Tube 4mm x 0.45mm x 3.1mm 3
AT5M Aluminium Tube 5mm x 0.45mm x 4.1mm 2
Code Type Outer Dia x Wall x Inner Dia Piece(s)
CT1M Copper Tube 1mm x 0.25mm x 0.5mm 4
CT2M Copper Tube 2mm x 0.45mm x 1.1mm 4
CT3M Copper Tube 3mm x 0.45mm x 2.1mm 4
CT4M Copper Tube 4mm x 0.45mm x 3.1mm 3
CT5M Copper Tube 5mm x 0.45mm x 4.1mm 2
Code Type Outer Dimensions Piece(s)
SFT1 Slide Fit Brass Tube Pack 0.4mm, 0.6mm, 0.8mm, 1.0mm 1 pc of each
SFT2 Slide Fit Brass Tube Pack 0.3mm, 0.5mm, 0.7mm, 0.9mm 1 pc of each
SFT3 Slide Fit Aluminium Tube Pack 0.4mm, 0.6mm, 0.8mm, 1.0mm 1 pc of each
SFT4 Slide Fit Aluminium Tube Pack 0.3mm, 0.5mm, 0.7mm, 0.9mm 1 pc of each
SFT5 Slide Fit Nickel/Silver Tube Pack 0.4mm, 0.6mm, 0.8mm 1 pc of each
SFT6 Slide Fit Nickel/Silver Tube Pack 0.3mm, 0.5mm, 0.7mm 1 pc of each
SFT7 Slide Fit Brass Tube Pack 1.2mm, 1.4mm, 1.6mm, 1.8mm 1 pc of each
SFT8 Slide Fit Brass Tube Pack 1.1mm, 1.3mm, 1.5mm, 1.7mm 1 pc of each
SFT9 Slide Fit Brass Tube Pack 1mm, 2mm, 3mm 1 pc of each
SFT10 Slide Fit Brass Tube Pack 4mm, 5mm, 6mm 1 pc of each
Code Type Outer Dia x Wall x Inner Dia Piece(s)
MBT03 Micro Brass Tube 0.3mm x 0.1mm x 0.1mm 3
MBT04 Micro Brass Tube 0.4mm x 0.1mm x 0.2mm 3
MBT05 Micro Brass Tube 0.5mm x 0.1mm x 0.3mm 3
MBT06 Micro Brass Tube 0.6mm x 0.1mm x 0.4mm 3
MBT07 Micro Brass Tube 0.7mm x 0.1mm x 0.5mm 3
MBT08 Micro Brass Tube 0.8mm x 0.1mm x 0.6mm 3
MBT09 Micro Brass Tube 0.9mm x 0.1mm x 0.7mm 3
MBT10 Micro Brass Tube 1.0mm x 0.1mm x 0.8mm 3
MBT11 Micro Brass Tube 1.1mm x 0.1mm x 0.9mm 3
MBT12 Micro Brass Tube 1.2mm x 0.1mm x 1.0mm 3
MBT13 Micro Brass Tube 1.3mm x 0.1mm x 1.1mm 3
MBT14 Micro Brass Tube 1.4mm x 0.1mm x 1.2mm 3
MBT15 Micro Brass Tube 1.5mm x 0.1mm x 1.3mm 3
MBT16 Micro Brass Tube 1.6mm x 0.1mm x 1.4mm 3
MBT17 Micro Brass Tube 1.7mm x 0.1mm x 1.5mm 3
MBT18 Micro Brass Tube 1.8mm x 0.1mm x 1.6mm 3
MBT19 Micro Brass Tube 1.9mm x 0.1mm x 1.7mm 3
MBT20 Micro Brass Tube 2.0mm x 0.1mm x 1.8mm 3
Code Type Outer Dia x Wall x Inner Dia Piece(s)
NST03 Micro Brass Tube 0.3mm x 0.1mm x 0.1mm 2
NST04 Micro Brass Tube 0.4mm x 0.1mm x 0.2mm 2
NST05 Micro Brass Tube 0.5mm x 0.1mm x 0.3mm 2
NST06 Micro Brass Tube 0.6mm x 0.1mm x 0.4mm 2
NST07 Micro Brass Tube 0.7mm x 0.1mm x 0.5mm 2
NST08 Micro Brass Tube 0.8mm x 0.1mm x 0.6mm 2
NST09 Micro Brass Tube 0.9mm x 0.1mm x 0.7mm 2
NST10 Micro Brass Tube 1.0mm x 0.1mm x 0.8mm 2
Code Type Outer Dia x Wall x Inner Dia Piece(s)
BT1M Copper Tube 1mm x 0.25mm x 0.5mm 4
BT2M Copper Tube 2mm x 0.45mm x 1.1mm 4
BT3M Copper Tube 3mm x 0.45mm x 2.1mm 4
BT4M Copper Tube 4mm x 0.45mm x 3.1mm 3
BT5M Copper Tube 5mm x 0.45mm x 4.1mm 2
BT6M Copper Tube 5mm x 0.45mm x 5.1mm 2
BT7M Copper Tube 5mm x 0.45mm x 6.1mm 2
BT8M Copper Tube 5mm x 0.45mm x 7.1mm 2
BT9M Copper Tube 5mm x 0.45mm x 8.1mm 2
BT10M Copper Tube 5mm x 0.45mm x 9.1mm 2
Code Type Outer Dia x Outer Dia x Inner Dia Piece(s)
SSB1M Square Brass Tube 1.6mm x 1.6mm x 0.9mm 3
SSB2M Square Brass Tube 2.4mm x 2.4mm x 1.6mm 3
SSB3M Square Brass Tube 3.2mm x 3.2mm x 2.4mm 3
SB1M Square Brass Tube 3.96mm x 3.96mm x 3.2mm 2
SB2M Square Brass Tube 4.76mm x 4.76mm x 3.96mm 2
SB3M Square Brass Tube 5.55mm x 5.55mm x 4.76mm 2
SB4M Square Brass Tube 6.35mm x 6.35mm x 5.55mm 2
Code Type Outer Dia x Outer Dia Piece(s)
SBW10 Square Brass Rod 1mm x 1mm 4
SBW15 Square Brass Rod 1.5mm x 1.5mm 3
SBW20 Square Brass Rod 2mm x 2mm 2
SBW25 Square Brass Rod 2.5mm x 2.5mm 2
SBW30 Square Brass Rod 3mm x 3mm 2
Code Type Dimension Piece(s)
BW02 Brass Rod 0.2mm 10
BW03 Brass Rod 0.3mm 10
BW04 Brass Rod 0.4mm 10
BW045 Brass Rod 0.45mm 10
BW05 Brass Rod 0.5mm 10
BW08 Brass Rod 0.8mm 9
BW10 Brass Rod 1.0mm 9
BW15 Brass Rod 1.5mm 7
BW20 Brass Rod 2.0mm 5
BW25 Brass Rod 2.5mm 4
BW30 Brass Rod 3.0mm 3
Code Type a x b x c Piece(s)
IB2 Brass I Beam 1mm x 2mm x 1mm 1
IB6 Brass I Beam 3mm x 6mm x 3mm 1
Code Type Dimensions Piece(s)
BS1M Brass Strip 6mm x 0.4mm 5
BS2M Brass Strip 12mm x 0.4mm 4
BS3M Brass Strip 25mm x 0.4mm 3
BS4M Brass Strip 6mm x 0.6mm 4
BS5M Brass Strip 12mm x 0.6mm 4
BS6M Brass Strip 25mm x 0.6mm 3
BS7M Brass Strip 6mm x 0.8mm 4
BS8M Brass Strip 12mm x 0.8mm 3
BS9M Brass Strip 25mm x 0.8mm 3
BS10M Brass Strip 25mm x 1.6mm 1
Code Type Dimensions Piece(s)
NSR1 Nickel Silver Rod 0.1mm 10
NSR2 Nickel Silver Rod 0.2mm 6
NSR33 Nickel Silver Rod 0.33mm 6
NSR45 Nickel Silver Rod 0.45mm 5
NSR6 Nickel Silver Rod 0.6mm 5
NSR7 Nickel Silver Rod 0.7mm 5
NSR9 Nickel Silver Rod 0.9mm 5
NSR10 Nickel Silver Rod 1.0mm 5
Code Type Outer Dia x Wall x Inner Dia Piece(s)
MAT03 Micro Aluminium Tube 0.3mm x 0.1mm x 0.1mm 2
MAT04 Micro Aluminium Tube 0.4mm x 0.1mm x 0.2mm 2
MAT05 Micro Aluminium Tube 0.5mm x 0.1mm x 0.3mm 2
MAT06 Micro Aluminium Tube 0.6mm x 0.1mm x 0.4mm 2
MAT07 Micro Aluminium Tube 0.7mm x 0.1mm x 0.5mm 2
MAT08 Micro Aluminium Tube 0.8mm x 0.1mm x 0.6mm 2
MAT09 Micro Aluminium Tube 0.9mm x 0.1mm x 0.7mm 2
MAT10 Micro Aluminium Tube 1.0mm x 0.1mm x 0.8mm 2

Thanks to
This article uses material from the Wikipedia articles “Coaxial_cable” and “Speed of light”, which are released under the Creative Commons Attribution-Share-Alike License 3.0.