Yagi antenna designer.

Uda Yagi Antenna dimension calculator

Back to Antenna calculator overview.

On-line directional antenna designer. Unlike most antenna designs on this site which are omni directional, this antenna type is very directional and has been constructed to facilitate the reception of telemetry signals from the smart falconry telemetry project. Calculate the required dimensions for a three to eleven element directional yagi antenna construction for any given frequency.

Enter the required frequency in MHz and the antenna designer will calculate the dimensions of the required elements as shown below.

Enter Frequency (MHz)

The amount of antenna elements (the more elements the more (inverse log) gain it has and directional beam becomes more narrow.)

Boom diameter BD in millimeters (the diameter of the PVC pipe where the antenna elements will be mounted on)

Antenna elements diameter ED in millimeters (the diameter of the antenna elements)

The Yagi antenna is a directional antenna using parasitic director and reflector elements to amplify the radio frequency signals from the direction it is pointing. The more parasitic director elements (up to a point) added will increase the DB (gain) and narrow the receptive beam width. It is different from the other antenna types because of this 'one direction reception'.

Performs very well and can be used for RX and TX purposes. Construction materials for UHF/VHF are PVC plumbing pipes and joints and aluminium melding rods, although heavy gauge copper wire is also suitable.

Frequency calculations are based on radio waves traveling at the speed of light 299 792 458 meters per second.

Yagi Antenna Design

Yagi directional antenna design illustration.

Notes about the Yagi antenna calculator

* Boom length: BL The boom length should be more than is calculated as this distance is measured from the center of the reflector to the center of the last director. It stands to reason that more length is needed to mount these elements to the boom and you might want an area behind the reflector to mount the antenna itself. Second to note about the boom is that it is assumed to be made of non conductive material, like PVC piping. Do not use aluminium tubing or other metal materials for the boom..

** Dipole connection : The impedance at the center of a dipole is about 73 Ohm, and that of an open folded dipole about 292 Ohm. To connect this to 50 Ohm transceivers we need transformers to convert 73 and 300 Ohm to 50 Ohm. A separate section deals with connecting the driven active antenna element to a 50 Ohm transceiver via coax. This antenna design calculates a single dipole rod as active element a gamma match would be the simplest way to connect it to 50 Ohm transceivers. Gamma matching is used for the falconry telemetry system as the single rod dipole has a narrow bandwidth which is exactly what is needed when tracking a very specific frequency. If however you are a radio amateur operator and want an antenna with more bandwidth, then a folded dipole can replace the active element of this antenna design.

Gain calculation and why approximate. The gain calculation is based on four formulas to calculate the gain for directional yagi type antennas. Each one gives its own results. This antenna calculator uses all four and then divides the results by four giving the average.

  • (David VK3AUU) 3.39 * Math.Log(('amount of elements' - 1) * 0.2) + 9.15 =
  • (Ring WA2PHW) 10 * Math.Log(5.4075 * (('amount of elements' - 1) * 0.2) + 4.25) / Math.Log(10) =
  • (Bertelsmaier DBJ9BV)7.773 * Math.Log('amount of elements' - 1) / Math.Log(10) + 9.28 =
  • (Rothammel p439 11th ed.) 3.39 * Math.Log('for each element count -2 in separation distance (per element)') + 9.15 =

Antenna matching the driven element

Gamma match
One of the simplest methods of matching a dipole to 50 Ohm coaxial cable. The adjustment point to get the SWR as low as possible is around 0.05 lambda. The recommendation is that the matching rod is half the thickness of the dipole material, however using the same material as the dipole has minimal effect on the sweet spot.

Gamma Matching Illustration
Gamma Matching
Gamma Matching Construction
Gamma Matching Construction
Gamma Matching Construction
Gamma Matching Construction
Five element 433 MHz yagi antenna
Yagi antenna feed point

Yagi active element

Yagi construction

Yagi gamma matching

Completed Yagi Antenna

Completed Yagi Antenna