Re: uBITX full design

Jerry Gaffke


Be aware it might not be as trivial as it looks.

The transformers are described here:
Search for "Coil Details".

The KiCad files are not available, that was some sort of requirement
when they set up HFSignals to build this stuff.
Perhaps to get a business loan they had to keep some part of the design private.
The remainder of the design is open source, and building from scratch is encouraged.
The uBitx is a two layer board, the bottom side is mostly ground plane.
Perhaps just build "ugly style" or "Manhatten style" on copper clad circuit board,
that way you have a solid ground plane under the entire design, which is highly recommended.

All quartz crystals in that IF filter should be matched by hand to within 100hz or so,
that means building a crystal oscillator and having some way to accurately measure frequency..
If your quartz crystals have different characteristics than what hfsignals uses,
you will need some way to determine the passband of the IF filter and adjust the filter shape
as described in Experimental Methods in RF Design (and/or search for Dishal on the web).

You will need some way to sniff and measure RF, an Antuino would be ideal,
though you might get by with a diode RF probe and a Harbor Freight DVM.
A good scope would be nice, perhaps 50mhz or more of bandwidth.
The nanoVNA would be worth looking into, shows complex of 1 and 2 port networks,
and thus is an education in itself.

If you are serious about studying "RF and Microwave", all of the above is worth the investment.

And lastly, maybe get a working uBitx from hfsignals, so you can
know for sure what the signals levels really should be when yours does not work.

Many have built radios like the uBitx from scratch.
But few find it easy.

Jerry, KE7ER

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