Bitx Kit Transmitter Scope Waveforms

These voltages are what I would call "minimum". If you have more, it's probably good. With these voltages I was able to adjust the drive to get 12 watts out.

Unless otherwise noted, there is a 2 KHz, 50 millivolt signal applied to the mike input connector. If you have R92 on the board for electret mike voltage, be sure and capacitor couple the input signal. Something around 1-10 ufd should be great.

This is at the buttonhook of R77. R66 pot fully CW or CCW. What you are seeing is the 11 MHz BFO coupled back through T6 being varied at the 2 KHz rate. This is not modulated at this point. The 2 signals have been linearly added. For modulation to occur and new frequencies produced, there has to be a non-linear device. This will be the diodes, D14 and D15. We will have a modulated waveform, double sideband, at R66.

This is with R66 turned the opposite way. The 2 extremes may not give you the same voltage.

Buttonhook D13 with R66 at one end.

Buttonhook D13 with R66 balanced.

Buttonhook D11. The filter has removed the lower sideband.

Junction R14 - L10. We are now at 14 MHz. Adjusting the VFO should change the frequency slightly.

Buttonhook D2. If you don't have at least this much signal voltage. You won't be able to get enough drive.

Junction C11-C13. The adjustment of C14 and C18 will have a great effect on the signal level. You want to adjust them at the frequency that you use the most.

Junction R83 - Q20. With this much voltage, you should be able to drive the PA to 10 - 12 watts out with the drive pot less than 3/4th's full CW. The adjustment of the PA bias is very sensitive and if you are unable to get full power out, reset and readjust.