Recently, I have received an antenna from one of the Chinese manufacturers and they haven't disclosed the detailed specification.

Below is the picture of my antenna (please ignore the specification in the picture):

enter image description here

The specifications that are provided by the vendor are over here.

  • Frequency: 865-867 MHz
  • Gain: 3 dBi
  • VSWR < 3.0 : 1
  • Radiation Pattern: Omnidirectional
  • Impedance: 50 ohm
  • Length (From connector to Antenna End): 500 mm

I want to know from its size and gain, can we predict its antenna type (e.g. Collinear antenna), its design (dipole or mono-pole), internal construction, polarization and various other parameters?

These kinds of antennas look to be standard and I think others who have used them in the past can help me in identifying my own antennas. I am waiting for my manufacturer to share detailed specification but I am not sure how long will they take.


According to my calculations, the wavelength for 865 MHz signal would be 0.35 m. So, for half-wave dipole, the length should be 0.17 m. However, length of my antennas is bigger than that. I think that's why it is collinear dipole array antenna. Please correct me if I am wrong.


2 Answers 2


The length implies that the antenna is approximately a wavelength long - enough to fit two elements in some sort of collinear array.

An ideal collinear array would have a gain of around 4-5 dBi. Factor in 1-2 dB loss for non-ideality and the previous poster is probably right in assuming that it is a collinear array.


It's most likely some kind of co-linear array of dipoles.

The lack of a ground plane means it's not a monopole. And as you've calculated, it's substantially physically longer than a half-wave dipole would be. Further supporting the notion of some kind of array, the indicated gain of 3dBi is greater than the gain of a simple half-wave dipole (2.15 dBi).

  • $\begingroup$ Since it takes single ended RF signal. Does it have internal balun? $\endgroup$
    – abhiarora
    Oct 30, 2018 at 19:45
  • $\begingroup$ if you will, yes, it does, in the shape of a defined length of outer conductor "folded inside out". $\endgroup$ Oct 30, 2018 at 20:02
  • $\begingroup$ indeed, quite likely of the "bazooka" balun variety: antenna-theory.com/definitions/bazooka.php $\endgroup$ Oct 30, 2018 at 21:07

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