What's all this antenna dB stuff really mean?

dB on it's own is actually meaningless. dB is a relative measurement. So an antenna with 3dB gain doesn't mean anything, but you can say that a 6 dB antenna will receive twice as much signal as a 3dB antenna. See what we mean about "a relative measurement"???

To confuse things further there is the dBi and dBd (amongst others!) - dBi means the antenna is being compared to a perfect antenna that transmits / receives equally in all directions. This type of antenna is only in theory and can't ever be built, but it is a good reference point. dBd, seen less commonly, refers to a perfect "dipole" antenna - this is an antenna with two "arms" - a bit like the old rabbit ear antennas on old televisions. Any antenna that is measured in dBd will have 2.15dB more gain - or amplification compared to an antenna measured in dBi

How much is a dB?

Well that all depends on what you are measuring (sorry!). But what we can say is that every 3dB doubles the signal. So 3dB is twice the signal and 6dB is four times the signal, and so on...

3dB = x 2 (eg. Blackhawk Shark Fin Antenna)

6dB = x 4 (eg. Blackhawk Trucker Antenna)

7dB = x 5 (eg. Blackhawk Marine Antenna)

10dB = x 10 (Just for reference)

11dB = x 12.5 (approx) (eg.LPDA and Caravan Yagi)

14dB = x 25 (approx) (eg. our 14dB Blackhawk Yagi)

So from this you can see that the Blackhawk Yagi works more than 12 times better at pulling in signals than the Shark Fin Antenna, and twice as much compared to the LPDA.

But be careful - not all antennas have the same gain (dB) at all frequencies. For example the LPDA antenna will provide it's gain across a host of frequencies whereas the Blackhawk Yagi is only useful for NextG and 4GX (Telstra 3g/4G)

And here is a good, "rule of thumb" - the more gain an antenna has the more directional it is. Antennas that receive all around (omnidirectional) - like the Trucker Edge Antenna and Marine antenna will usually have a gain of around 3 - 7 dB. Antennas with high gains, like the LPDA and Yagi, must be pointed to where the signal is coming from.

So whilst we use the term "dB" all the specifications on our site are in dBi - which is comparing the antenna with the "perfect" antenna. This makes it easy to compare the antennas with each other and from different manufacturers.

 

 


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