3 ms·

I'm not ham operator so I'm just guessing here, but they may be talking about interference at the receiver. The new signal may be so strong and near enough ham

I'm not ham operator so I'm just guessing here, but they may be talking about interference at the receiver. The new signal may be so strong and near enough ham band, that even after attenuation by typical band-pass filter it's still the strongest component and will overwhelm input stage amplifier. Trivial solution for that would be adding a band-stop filter tuned for the frequencies used for HFT but that again may add noise and attenuate nearby frequencies.

wbl 3y ago
In HF the limiting noise is not receiver generated unlike in microwaves and (ideal) capacitors and inductors don't generate noise: resistors and active components do. However a sharp notch is a real pain to make in analogue domain. Lots of stages, temperature changes the component values, and things get bulky.