uBitx Unfiltered

Warren Allgyer
 

I made the attached files for my own reference during work on my uBitx which I have now suspended. But I thought they might be helpful for those still engaged in trying to filter the radio with external LPF/BPF combinations. This was my uBitx with the filters completely removed so I could see what parameters would be needed for an external filter to work satisfactorily. There are four slides included. Here are my comments on each:

80,40,20 meter CW
- Power level set on each band individually to 5 watts
- Green display line represents the -43 dBc threshold
- Second harmonic on both 80 and 40 is somewhat problematic as are odd harmonics out to 13th

80,40,20 meter SSB
- Power level set on each band individually to 5 watts CW then 1 kHz tone input level adjusted to produce the same 5 watts
- Green display line represents the -43 dBc threshold
- Second harmonic on both 80 and 40 is somewhat problematic as are odd harmonics out to 9th

17, 15, 10 meter CW
- Power level set on each band individually to 2 watts
- Green display line represents the -43 dBc threshold
- Harmonics can all be removed with a simple 34 MHz LPF. The filter included in the uBitx is more than adequate

17, 15, 10 meter SSB
- Power level set on each band individually to 2 watts CW then 1 kHz tone input level adjusted to produce the same 2 watts
- Green display line represents the -43 dBc threshold
- 17 meter spurs represented by markers 1 and 2 are problematic because only a close spaced, single band BPF can be used to remove them.
- 15 meter spurs at the low end need to be addressed.
- A single filter cannot cover these bands because of the close spaced 17 meter spurs.
WA8TOD

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