The MFJ-1048 Transceiver Passive Preselector 1.6-33 MHz MFJ Passive Preselector has an extremely high dynamic range! It improves the performance of nearly any HF or shortwave receiver/transceiver. It vastly improves the most expensive receivers. It is beneficial to those with broadband front-ends prone to overload. Protects your sensitive receiver input from damage (including switching diodes and attenuator resistors) caused by strong signals from multi-transmitter, multi-band operation -- contests, field day, nearby hams, CBers, TV/FM/AM stations.
It eliminates phantom signals by suppressing strong out-of-band signals that cause intermod, blocking, and cross-modulation. It also eliminates second-order intermodal problems caused by out-of-band solid shortwave broadcast signals mixing and producing unwanted in-band signals.
MFJ's unique Hi-Q series tunable circuit gives you superb performance. The tunable series-tuned circuit works into a very low impedance formed by broadband toroidal transformers.
It has a narrow bandwidth, excellent stopband attenuation, low loss, and constant bandwidth and gain over each band. It also has excellent attenuation in adjacent contest bands.

The entire 1.6 to 33 MHz HF band is covered in five overlapping bands. An RF sense transmit/receiver switch w with adjustable time delay automatically bypasses your MFJ-1048 when you communicate. It also has PTT line T/R switching. Plugs between antenna and transceiver. Fully shielded metal enclosure. It has a tough black finish.