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Yaesu FT-1000D

Yaesu's classic, top of the line HF transceiver for contesters and DXers is
probably the only ham dual-receiver radio that does true diversity reception

The KD5VC 250Hz Filter Mod

The FT1000D comes equipped with additions including IF Filters for the 455KHz c.f. The narrowest of these has a 500Hz bandwidth, but no matching filter for the 250Hz bandwidth for the 455KHz IF This means that if you select the 250Hz bandwidth filter in the second IF, it is paired with the 2.4KHz filter in the third IF. It is a simple modification to have the control section select the 500Hz filter in the third IF instead.

This modification requires the addition of a switching diode (1N4148, 1N918 etc.) between the select line on the 250Hz filter spot and the 500Hz filter.

First, access the filters on the IF board, and clip the diode as indicated for the installation of the 250Hz filter in the manual. Then remove the 500Hz filter, note that the IF filter position for the 500Hz filter is the second from the front of the radio.

Then solder the diode between the cathode end of the 250Hz select diode, and the cathode end of the diode under the 500Hz filter. This diode should be oriented with the cathode toward the 250Hz select diode's cathode end.

Now when the 250Hz third IF control pulls the select line low, the new diode will pull the 500Hz filter select line low, selecting that filter in place of the 2.4Khz filter. When you finish this modification you will note that the 500Hz filter reduces the wideband noise, and the "Width" control works when the 250Hz filter is selected.

Because of the mismatch in the filter bandwidths, the first few detents on the width control act as an IF shift, when the 500Hz filter is offset enough to "catch up" with the bandwidth of the 250Hz filter, the action changes to a bandwidth control. On my radio, the first three detents act as an IF shift, and the next three reduce the bandwidth to under 100Hz.

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