EME211 Attenuator / 9MHz Trap Kit
The Mini-Kits EME211 RF Attenuator and Trap Filter module that is used ahead of the receivers RF amplifier and mixer, and is part of the M1 series building blocks to construct a high performance M1 HF Transceiver, but can also be used as a general purpose 6dB per step switchable attenuator. The attenuator uses two relays to provide attenuation steps of 0dB, 6dB, 12dB, and 18dB. The 9MHz trap uses high Q tuned circuits that when carefully aligned, provides greater than 50dB of attenuation at 9MHz while keeping loss less than 0.4dB at 7.3MHz. See the M1 Transceiver Block diagram on where this module is used.
The M1 HF Series Kits have been designed to allow easy construction due to the use of mainly leaded components for those that don't like surface mount devices. SMD components are only used when required due to availability of components, or for better performance. The RF modules are all designed with a 50ohm impedance making it easy to interconnect with the other M1 series modules, and your own home brew circuit designs.
The images below show both sides of the board. The module uses a number of tiny SMD devices that could not be avoided as it was not easy to get all the required components onto the small board.