Is that a limitation of the antenna? I though QuadRF uses SDR so can see many frequencies, not just the wifi things like ESPARGOS [0]

From documentation, QuadRF: Operating frequency range of 4.9 - 6.0 GHz (C-Band).

0. https://espargos.net/

Not the antenna, unfortunately, it only operates on the range of 4.9-6ghz.

It would be great to have a wider range like other SDRs but of course the cost will increase exponentially.

https://www.crowdsupply.com/scale-rf/quadrf