The myth of specific channel “tuned” antennas

The myth of specific channel “tuned” antennas

I often get asked on which channel X or Y antennas are tuned too. The short answer is: There’s no such thing as a tune so specific that it encompass a single channel, for hobbyist at least.

The long answer is a perfect tune on a certain channel won’t make any difference as the bandwidth of most antennas in FPV is way too large to matter. In other words, if you can reach a perfect tune in the first place, then all other channel will be “good enough”. What is “tune” after all? The frequency of perfect SWR might not be the frequency of best efficiency or best gain or axial ratio, ect. As in my previous post about SWR: An antennas with 2:1 SWR and 98% efficiency will still do better than an antennas with 1.01:1 SWR and 75% efficiency. More accurately, the “tune” of antennas would be where all desired characteristics happen together in good enough value. SWR is relatively easily measured in an antenna and thus erroneously taken as the only metric that mater.

Take example this S11 (similar to SWR) measurements of our older model X-air taken by Maarten Baert:

One could be tempted to say the best tune is at 6GHz, however the nature of theses antennas place the best gain and best axial ratio not at the best SWR, but in the center of that somewhat W shape (green area).  That “tune” range in the green area cover all channels of the 5.8GHz band and then some. So no channel will get measurably better reception than any other.


“But if the best gain was at 6GHz where SWR is 1.05:1, that would be better right?”

-That would be around 0.25% better in terms of range.

“When I fly on X channel I get worse range than Y?”

-A nearby transmitter may reduce your range on specific channel(s), not related to antennas. Also, Vrx sensitivity and Vtx power level do change from channel to channel.

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