Category Archives: 630m

VK5ZVS 630M Band Pass Filter using transistor radio IFTs

I’ve included 630 meters in my 8 band Progressive Receiver project. Not that I expect to hear much LF CW, but down the track I hope to hook up a shack computer for FT-8, WSPR or whatever weak signal digi mode they use down there. 630m is a playground for homebrew transmitters and receivers. For example, Dimitris VK1SV has some simple but impressive class E transmitters using the familiar IRF5xx switching FETs. You can get a lot of bang for your buck out of any transistor or FET operating at 470kHz. So including 630m in my receiver creates opportunities for future play!

Using metal can transistor radio IFTs as the tuned elements of a BPF is just such an obvious and neat idea. A pack of four IFTs is available from Jaycar, three cans for the 455kHz IF and one (red) for the oscillator. VK1SV built a 630m filter with two, whereas Steph VK5ZSV went as far as five. My filter uses four, mainly because the white ones come 2 in a pack, so my investment was 2 packs (about $10). The video shows a band scan with the filter out, then in. Thanks to VK1SV and VK5ZVS for publishing their designs on their sites.

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