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.
DDS IF board generates the proper IF signal depending on mode and filter selection.
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.
Click on picture to enlarge
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)