开云体育

Hi.

Just an update for everyone about the modifications suggested by Wolfgang DK4RW to ensure clean switching in full break-in mode. This involved reducing the base emitter resistor R41 with a lower value (235 Ohms) and also replacing C22 with a 0.1uF capacitor to remove the audio key clicks experienced with my 17Mtr board when set in full break-in mode. I have also noticed that one processor fails to boot up with 12v supply but switches on every time with 13.8 volts without any mods being done!

It is a pity only one board out of three worked "straight out of the box" so to speak without any modifications being made to ensure clean switching of the TX. However, in spite of the above modifications enabling the boards to be used effectively on CW using the Iambic B setting and full break-in, the semi break-in setting still results in? a tone generated between the individual characters.

I am prepared to live with this for the moment but would like to know if you have also experienced this self oscillation/RF feedback and if anyone has any ideas about how this oscillation is being generated. Self oscillation, RF feedback, or timing ? It would be nice to know where to start. Thanks for the excellent scope traces Wolfgang.

In answer to those who questioned if the toroids supplied in later revisions had any differences, I can only go on appearances. They are all colour coded as the same "mix" but visually there does appear to be? some difference. Slightly thicker and sharper edges?

G QRP data on winding these filters suggest a margin of 5% for the windings anyway so I think it is much more important to ensure the windings are evenly spaced around the whole toroid and the enamel is cleanly removed and neatly soldered.

? ? ?? Original 20 Metre board which became unstable.

? ?? Newer board with modifications.

Any information about keyer output and waveform differences due to experimentation and modification is very welcome.

Derek G4VWI.