Re: Softrock 6.2 lite 30Meters
- The problem turns out to be that, in my opinion, a 2N3906 (Ft = 250
MHz)is a marginal device at 40.5 MHz in this application. I replaced
it with an MPSH81 (Ft = 600 MHz) and the peak-to-peak output voltage
increased to 4.8V and it toggles the '74 divider nicely.
The MPSH81 has a different pin-out, so the B and E leads have to be
swapped, which can be easily done with a short length of Teflon tubing
--- In email@example.com, "Jack Smith" <Jack.Smith@...> wrote:
> Built 6.2 Lite for 30 meters this afternoon and I have a problem with
> the 40.5 MHz crystal oscillator output.
> Q2's collector shows about 2.7V PP output at 40 MHz, insufficient to
> toggle U2. (10x probe, 100 MHz oscilloscope. Can use an FET probe and
> 400 MHz scope if necessary, but this is not a case of the scope probe
> loading Q2, as U2's output is not toggling without probing Q2.)
> I plugged in a 13.5 MHz crystal and see 4.8V PP out of Q2 into U2,
> with U2 and U3 toggling as they should, 6.75 MHz out of U2 and 3.875
> MHz out of U3.
> I've checked the component values once, and will re-check them
> tomorrow when I'm fresh, but I wondered if anyone else has seen this
> Jack K8ZOA