Hi gang...
??? I'm new to this list and coming up to speed on BITX40 mods. I started looking at the Raduino software to add a rotary encoder for improved tuning control, when I learned of this group a couple of weeks ago. I've since incorporated the Raduino 1.24 (maybe 1.25) software. Tuning is much improved, and many features have been added. I have stalled at making some of the hardware mods to the board until I can verify and understand the added features.
??? Starting first with an observation that may prove beneficial during troubleshooting that I didn't find in the history. I discovered that the multi-filar transformer windings are twisted many times more than necessary; putting them at risk of failure. This caused the enameled wire insulation to rupture and induce a part fart (R70) on my board after only a brief period of operating. A scan of the remaining transformers revealed this exposure exists on all of them. It's a bit of a pain to rewind and replace them in their mounting headers, so I've made a mental note to check them first when troubleshooting for failures down the road. I also think I alerted Farhan to this in an email, so new builds may have been screened for this.
??? CW is a mode of choice for me, so I was quite pleased to see early software support for this in Allard's most recent releases. I have been studying the hardware and Raduino software, and reviewing the posts relating to the mods. I struggled with understanding how the CW mode was implemented, but finally sorted it out. I'm confident that it works, but it uses a somewhat convoluted scheme to add (LSB) or subtract (USB) the sidetone frequency so the displayed transmit and receive frequencies match. :-)
??? I read that a "Pop" issue induced during PTT operation, has been identified and isolated with confidence to the powering up the Mic amp (Q12) as the root cause, but I'm uncertain it was resolved. Has anybody attempted to replace or bridge R127 with a forward biased diode (anode toward TX)? This snubs the R127/C124 (10 ms time constant) power-up delay by enabling C124 to charge instantly to within 0.7V of supply, and well within Q12's normal operating bias range. If this is indeed the root cause for the pop, the diode will prevent it.
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72
Gary, N3GO
