You need:

• SMA Pigtail with your desired coax length, the cable I used is RG316
• Plastic antenna tube (found some made by Reely here in Germany, 380mm long)
• Two pieces of wire each 200mm long, I used AWG28
• Hotglue

Mark the center on the antenna tube and use a solder iron to make a small hole in the tube right at the center. Do not cut the tube in half, this will give a better mechanical stability.
Prepare the open end of the SMA pigtail. Keep the feedpoint cap as short as possible.

Solder the two pieces of wire to the coax open end. Be sure the center wire will not touch the outer shielding.

Pull the wires through the antenna tube and the coax open end into the tube hole.
Then apply some good amount of hotglue to strengthen this point.

Cut the antenna tube including the wires inside to an overall length of 300mm. Each half of the tube to 150mm.

On my EZ* I sticked the dipole through the wing. On the lower end, the antenna tube (and only the tube!) was cut and put back together using silicon fuel tube (from nitro engines). This way it’s flexible and will not break in case of ground contact during landing.

A last helix to cover all interesting frequencies for FPV.

Antenna dimensions:

• Design frequency 2450MHz
• 8 turns
• Wavelength 0.23
• Internal diameter 41mm
• Wire diameter 2.5mm
• Coil spacing 28mm
• Reflector diameter 80mm
• Wave Trap size 15.2mmx7.6mm
• Feed point height 5mm (wire center), see pictures

My internal helix diameter is roughly 80mm with a coil spacing of 55.5mm. Wire diameter is 3.5mm/10mm².
Reflector size is 250mmx250mm. Center support is made from 6mm Balsa, soaked with epoxy resin.
For matching the IBCrazy wave trap method is used. Trap size is 30mmx15mm. See also http://www.rcgroups.com/forums/showthread.php?t=1377791

Designed for ground station use, the antenna was made after the following tutorial from IBCrazy:

http://www.rcgroups.com/forums/showthread.php?t=1352583

0.75mm² copper wire was used for the antenna elements, some hot clue to fix everything and a piece of PVC tube to keep the antenna away from any metal parts of the tripod.

Due to fragility of the copper wire a Styrofoam ball will be used as a protection radom.

62mm is used as quarter wavelength.

Angle (green one) between the “eyes” on one S-shaped wire is 78-80°.
The angle (blue one) of quarter wave sections is 100°.

About fine tuning I found the following:
Green angle >90° will lower the resonance frequency while angles <90° will result in a higher resonance frequency.

Measuring results after proper tuning for 1240MHz:

Return Loss & VSWR

Construction details from calculation:

VK5DJ's YAGI CALCULATOR

Yagi design frequency =868,50 MHz
Wavelength =345 mm
Parasitic elements fastened to a non-metallic or separated from boom
Folded dipole fully insulated from boom
Director/reflector diam =4 mm
Radiator diam =4 mm

REFLECTOR
167 mm long at boom position = 30 mm  (IT = 77,5 mm)

RADIATOR
Single dipole 160 mm tip to tip, spaced 69 mm from reflector at boom posn 99 mm (IT = 74,0 mm)
Folded dipole 164 mm tip to tip, spaced 69 mm from reflector at boom posn 99 mm (IT = 76,0 mm)

DIRECTORS
Dir    Length    Spaced    Boom position    IT    Gain    Gain
(no.)    (mm)    (mm)    (mm)        (mm)    (dBd)    (dBi)
1    146    26    125        67,0    3,5    5,6
2    144    62    187        66,0    5,8    7,9
3    142    74    261        65,0    7,3    9,5
4    140    86    348        64,0    8,5    10,7
5    139    97    444        63,5    9,5    11,7

COMMENTS
The abbreviation "IT" means "Insert To", it is the construction distance from the element tip to the edge
of the boom for through boom mounting

Spacings measured centre to centre from previous element
Tolerance for element lengths is +/- 1 mm

Boom position is the mounting point for each element as measured from the rear of the boom and includes
the 30 mm overhang.The total boom length is 474 mm including two overhangs of 30 mm

The beam's estimated 3dB beamwidth is 53 deg

A half wave 4:1 balun uses 0,70 velocity factor coax and is 121 mm long plus leads
FOLDED DIPOLE CONSTRUCTION
Measurements are taken from the inside of bends
Folded dipole length measured tip to tip = 164mm
Total rod length =350mm
Centre of rod=175mm
Distance HI=GF=69mm
Distance HA=GE=87mm
Distance HB=GD=105mm
Distance HC=GC=175mm
Gap at HG=3mm
Bend diameter BI=DF=23mm

If the folded dipole is considered as a flat plane (see ARRL Antenna Handbook) then its resonant
frequency is less than the flat plane algorithm's range of 10:1
The cap between the dipole halfs at the feedpoint is not critical but should be less than 5mm.

The required balun is made from RG316 coax cable and calculated with a velocity factor of 0.7.

Feedpoint detail:

And finaly the plot of the VSWR measurment to proof the construction:

Material costs <10€.

Feel free to contact me if you have questions about the antenna.

More on the FPV Equipment  page.

I mostly finished my FPV antenna tracker. The mechanic part and basic control electronic are working fine now.

Read all details on my FPV Equipment Page.