The FM-24 and FM-25 are standard format ComPol boards. They are identical except that the FM-24 is crystal controlled and tuned manually. The FM-25 includes a digital frequency synthesizer and electronic tuning. The receivers have five tuned circuits between the antenna and mixer. This provides high rejection of off-frequency signals and minimizes overload problems. The gain distribution also minimizes overload while maintaining very high sensitivity. Following the mixer are two IF filters. The user has three bandwidth options: The first is wide, with low group delay time, for SCA applications. The second is normal, to get the best trade between bandwidth and fidelity. The third option is narrow, where performance is slightly compromised to provide very high adjacent channel rejection. It is often possible to receive distant stations on the adjacent to a local with this filter option.
The receivers include built-in 5 volt regulators. The 10-pin headers include an RSSI output that can be used for monitoring the signal level or operating a squelch circuit.