Re: cw filters

DD5ET
 

As seen by these answers so far, there are lots of options. If, like me, you'd prefer to go the kit or pre-built route, there are options from cheap and simple to expensive and more complex.

I personally built the Hi-Per-Mite from Four State QRP: http://www.4sqrp.com/hipermite.php. It's a 200 Hz (fixed bandwidth) CW filter kit that costs $25 delivered and is powered by a 9 volt battery. It can all fit in an Altoids tin or other similarly sized enclosure. I had ordered some jacks and small enclosures (about the size of a deck of cards) for another project and used them for this, too (see photo -- Altoids tin is for size reference -- email me for parts sources, if interested). As Jerry Gaffke indicated, it's easy to use because it connects between the uBITX and your headphones. And, since it's an external device, it can be used with any radio that has an audio out jack. I've used it with my uBITX and my Xiegu G90 and it works well. Once I add an on/of switch, it'll be complete.



If you want a wider (but still fixed) bandwidth, QRP Guys have a CW filter kit with a 600 Hz bandwidth for only $20: https://qrpguys.com/qrpguys-active-600hz-audio-filter. This kit even comes with on/off and in/out switches and two audio jacks. All you need to supply is an enclosure, if you want one, and a 9 volt battery.

SOTABEAMS has a slightly more expensive DSP audio filter kit (also available pre-built), but it is more flexible because it comes with selectable filter bandwidths: https://www.sotabeams.co.uk/dsp-audio-filter-units-ready-to-use/. Prices start around $60 if bought outside the EU (EU customers pay a 20% VAT).

SOTABEAMS also has their new Wolfwave audio processor, but that is probably overkill and starts at around $300 if bought outside the EU: https://www.sotabeams.co.uk/wolfwave-advanced-audio-processor/.

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