ADS-B Site Upgrade Reconditions

[geckoVN]

@Do I Need A Filter?

The space around ADS-B antenna contain not only 1090 MHz signals, but also lot of other signals at different frequencies. The closer the frequency of a signal to 1090 MHz, your ADS-B antenna picks it stronger. For example if there are three signals of equal strength, one at 144 MHz, 2nd at 850 MHz and 3rd at 950 MHz, the ADS-B antenna will pick 950 MHz one the strongest, 850 MHz one a bit less stronger, and 144 MHz one much fainter.

Sorry, but NO.
RF simply isn’t that straight forward.
It’s a beginners mistake to treat RF as DC

You need to take into account the mathematical relationship between two (or more) frequencies.
For example, a strong 364MHz signal could easily resonate a 1090MHz antenna and de-sence a receiver.

There is an old RF adage that says: " Every mixer can be an amplifier, every amplifier can be a mixer"
As we all know, the output of a mixer is four frequencies: the two fundamentals plus F₁
+F₂ and F₁-F₂
Using a simplified example: a high powered, FM station on 110MHz plus a local transmitter on 980MHz could produce 1090MHz inside your LNA and you’d never know why your system performed poorly.