TPU and Antennas

Free space reflection coefficient before and after each 5 th and up to 20 washing cycles

Many if not most of you have now seen the youtube video by painless 360, if not, go have a quick look then come back here:

What Painless360 asserts in this video is that TPU shifts the frequency of your video output akin to picking up R5 on F4. However, his assertion is false and the interpretation that it is of a significant impact or that it justifies a stop in the use of TPU as an antenna mount is also false.

What the data is really showing is a shift in the tune of the antenna. All antennas are tuned to a specific frequency range and within this range, there is a peak or peaks where the antenna performs best. FPV antennas are generally tuned to be most powerful at 5800Mhz. That is to say that the antenna will give it’s most powerful output on 5800.

So what effect does TPU have? TPU is a hygroscopic material and does absorb some water which is not RF transparent. As such, it has an effect of reducing the total output strength of the antenna, although minimally. Additionally, it shifts the ‘tune’ of the antenna, such that the best frequency for performance is 50-150mhz lower than intended. This is not like having your receiver set to the wrong channel but close enough, this is like flying behind an object which blocks some of the strength of your video. The output frequency stays the same but the signal strength is diminished.

This effect from TPU is negligible, especially when we’re talking about racing a minimal when talking about freestyle. This may come into effect with longer range flying, but more likely will just alter what the ideal channel for flying long distance is. The recommendation is always to use an antenna that extends further from the body, which you can do on a god_mode given that the hole in the AXII cup is SMA sized.

While I respect Painless 360, he got this one wrong.

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