Low pass filter kits can be had from QRPLabs or you can build your own. The QRPLabs instruction documents have all the values they use...it would be easy to roll your own on a piece of perf board. Or some of the members here offer circuit boards. The components are not expensive or hard to find (altho it might be more cost effective to order them from QRPLabs). Lots of info online or in the ARRL Handbook on design.
Or see the wiki for details on how to hack the existing filters on the uBitX (thanks to Allison, et al.).
See for more info on the kits (disclaimer...I have no financial interest in QRPLAbs, just a customer).
73... Mark AA7TA
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On 9/22/18 7:41 PM, ajparent1/KB1GMX wrote:
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Spurs are less an issue for 20M and below.
External low pass or transmitting band pass filters are responsible way to go.
