  Lasers with well controlled relative frequencies are indispensable for many
applications in science and technology. We present a frequency offset locking
method for lasers based on beat frequency discrimination utilizing hybrid
electronic LC filters. The method is specifically designed for decoupling the
tightness of the lock from the broadness of its capture range. The presented
demonstration locks two free running diode lasers at 780 nm with a 5.5 GHz
offset. It displays an offset frequency instability below 55 Hz for timescales
in excess of 1000 s and a minimum of 12 Hz at 10 s averaging, outperforming the
best reported instabilities of methods based on beat frequency discrimination.
The performance is complemented with a 190 MHz lock capture range, a tuning
range of up to 1 GHz, and a frequency ramp agility of 200 kHz/$\mu$s.
