Alison KB1GMX counts 5 different schematics for the µBITx, and that is not including the HF1 or minima (2014) designs that came before the µBITx. The design was evolutionary.
The first production boards were labelled “V3”. Two further iterations have been sold since, the “V4” and now “V5”.
- V1 and V2 models were prototypes, and were not marketed and sold
- V3 had the TDA2822 audio chip in it. One batch had issues, and would easily fail. This was the first production board from December 2017.
- V4 had discrete transistors for the audio section and test points were introduced in a number of locations on the board. Pads were also included to allow the RD16HHF to be used to replace the, as shipped, IRF510 finals. This board had issues with low audio output – more suitable for headphones than speakers.
- V5 changes the 12mhz IF local oscillator to 11.059 MHz, and uses the LM386 for audio. The Low Pass Filter layout and relay arrangement has been improved to reduce harmonic removal.
V3 and V4 are probably technically not fully compliant with emissions regulations in most countries (at least in the developed world). However, the low power output of the µBITx probably means that emissions will have resulted in few issues with interference in practice.
The effectiveness of harmonics, IMD and spur modifications incorporated in the V5 board have yet to be established across a selection of production boards. There are no doubt improvements, but the degree to which the product could be considered to be 100% compliant on all bands and all modes has yet to be established.
[Edited by uBITx.net]