  We have fabricated arrays of High-T$_c$ Superconducting Quantum Interference
Devices (SQUIDs) with randomly distributed loop sizes as sensitive antennas for
Radio-Frequency (RF) waves. These sub-wavelength size devices known as
Superconducting Quantum Interference Filters (SQIFs) detect the magnetic
component of the electromagnetic field. We use a scalable ion irradiation
technique to pattern the circuits and engineer the Josephson junctions needed
to make SQUIDs. Here we report on a 300 SQUIDs series array with loops area
ranging from $6$ to $60\ \mu m^{2}$, folded in a meander line covering a $3.5\
mm\times 8\ mm$ substrate area, made out of a $150$-nm-thick
$\mathrm{YBa}_2\mathrm{Cu}_3\mathrm{O}_7$ film. Operating at a temperature
$T=66\ K$ in a un-shielded magnetic environment, under low DC bias current
($I=60\ \mu A$) and DC magnetic field ($B=3\ \mu T$), this SQIF can detect a
magnetic field of a few $pT$ at a frequency of $1.125\ GHz$, which corresponds
to a sensitivity of a few hundreds of $fT/\sqrt{Hz}$, and shows linear response
over 7 decades in RF power. This work is a promising approach for the
realization of low dissipative sub-wavelength GHz magnetometers.
