630M Band Pass Filter using transistor radio IFTs

I’ve included 630 meters in my 8 band Progressive Receiver project (still under development after 5 years, but that’s a future post!). 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 a homebrew 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 for this band. 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.

2 thoughts on “630M Band Pass Filter using transistor radio IFTs

  1. Steph - VK5ZVS / VK5FQ says:

    Hi Paul, Saw your video. Thanks for the link. Well Done! The 630m filter pcb looks rather swish!!

    Liked by 1 person

    • Paul Taylor says:

      Thanks for making it first Steph. Its such a neat idea to repurpose 455khz IF transformers as the resonators in a tight BPF. And I didnt have to wind a single rurn on a toroid!

      Like

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