Alinco DX-77 bandpass filter improvement

Discussion in 'Amateur Radio News' started by Guest, Nov 15, 2000.

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  1. Guest

    Guest Guest

    Cornell Drentea writes

    The Alinco DX-77 is a great performer for its class (with an OIP3 of +20 dBm), but it can use better selectivity.

    An additional 8 poles IF crystal filter can be cascaded for 16 poles of sharp selectivity by mounting an identical filter with the one in the radio in serries without any additional modifications. The radio has sufficient AGC and TGC action to make up for the additional insertion loss.

    The extra filter is available from Alinco for around $65. To achieve the conversion, remove/unsolder the current filter from the radio by first removing the IF board. Be careful not to destroy the circuit board. If you are not handy, don't try this. The radio is rather miniaturized. Place the two filters back to back upright (rather than straight down)and touch solder them together to make one assembly. The connecting pins should face outwards. Do not hold the soldering iron for too long on the filters. Then, interconnect filters at the top to put them electrically in serries. Install wires at the bottom, and mount the entire assembly upright through the empty unsoldered pads on board. Solder the assembly in place. Make sure everything is clear of contacts. A little bit of glue at the bottom of the assembly will secure it to the board. This completes the modification. Reinstall all connectors and screws. If you did everything right, you will have a much better radio. The result is outstanding selectivity in receive and a better sound (more like a DX)in transmit.

    Good luck with the mod!

    73, Cornell Drentea - KW7CD
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