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IF Filter Board

The HW-5400 is a single conversion, 8.830 mhz IF radio and contains space for 1 Rx 4 pole crystal filter, and 1 Rx/Tx 6 pole crystal filter.
The original 6 pole filter is a 2.4khz wide filter (great for DX work). The optional 4 pole filter is a 1.8khz wide filter.
This project added an additional selectable crystal filter(s) to allow for wider audio transmit (eSSB) and/or reception.

Left Side:
DDS IF board generates the proper IF signal depending on mode and filter selection.

Right Side:
Filter board (perf board) Contains both the original 2.4khz and new 4khz & 6khz crystal filters and switching circuits.
Filter board (under perf board) Contains the tuned IF circuits, RX amplifier, ALC, and AGC circuits.

IF

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IF Filter board Design

 

Removed the original 2.4khz IF crystal filter from the IF board. Installed IN/OUT connectors on the IF board. Installed the original 2.4khz IF filter and a new 4khz IF filter on a homebrew PCB, the "IF SFB". Filter selection is done by the "LO DDS" board via the front panel keypad. A signal is sent from the "LO DDS" board to both the "IF DDS" and the "IF SFB". The "IF DDS" uses the signal to change the phantom carrier IF freq to the correct value for the selected filter. Mechanical low signal 12v relays on the "IF SFB" select either filter. The board is located over the top of the original IF board. (to keep the IF signals as short as possible)