  We present a simple and flexible frequency offset locking scheme developed
for high-field imaging of ultra-cold atoms which relies on commercially
available RF electronics only. The main new ingredient is the use of the sharp
amplitude response of a home-made RF filter to provide an error signal for
locking the lasers. We were able to offset lock two independent diode lasers
within a capture range of 200 MHz, and with a tuning range of up to 1.4GHz. The
beat-note residual fluctuations for offset locked lasers are below 2MHz for
integration times of several hundreds of seconds.
