In progress: Softrock Lite II, 40m

February 28, 2009 | Amateur Radio | By: Mark VandeWettering

I’m kind of at a position where I don’t know what to do, and I’m having a feeling that I shouldn’t be working on machinery today (the temporary knack muse has left me). I got the power supply and local oscillator installed, but I’m now at an block: when I powered up my Softrock with a current limiting resistor in place, I see a current of about 3.5ma, which seems within reason. I then power it up without, and see a current of 22ma, which is not so good (it should be less than 4ma) and no hint that it is oscillating when I tune in my FT-817 anywhere near the 28.224 Mhz that the oscillator should be running at. I measure the following voltages:

  • R11 hairpin: 4.92 volts, nominal, indicates that the voltage regulator is working.
  • R15 hairpin: 3.94 volts, nominal value should be < R11, mine is significantly lower than the supply voltage, might indicate a problem.
  • R12 hairpin: 2.37 volts, should < 2.5, seems nominal.
  • R17 hairpin: 4.7 volts, should be > 2.5, mine seems high perhaps.

I’m going to ponder it, and read through the softrock40 Yahoo! group for help.

Here are some pictures in the meantime.

Addendum: It oscillates! I found that I had a solder bridge across the leads of C12. Now, I can hear it LOUDLY in my FT-817, although the oscillator doesn’t sound all that smooth. Still, all it has to do is drive those flip flops, so I doubt it matters. Current draw is 13.6ma, which seems a bit high, at least if you take the builder’s guide as true, but it has a fairly obvious mistake, so I am not sure that I should trust his 1.8ma as true either. Still, I’ll go back and remeasure the voltages going forward, and take a bit of a break before I go onto the next round of adding SMT caps and ICs.

Addendum2: Coil, coil, toil and trouble. Man, making 38T through one of these coils is tough, even with #30 wire. Photographing it with a digital camera does make it easier to double check your work.



Comment from Leonard
Time 2/28/2009 at 3:34 pm

Robby’s current measurements are incorrect. I discussed it with him yesterday. His ma meter is toast! The best measurement is to measure the voltage drop across R11. Mine measured 90mv’s corresponding to 9 ma’s. Calculations say that is in the ballpark.

Comment from Eldon Brown
Time 2/28/2009 at 4:31 pm


This looks like a fun project, it will be great to hear/see it online.

73’s – Eldon – WA0UWH

Comment from Al Gordon
Time 5/23/2009 at 9:48 am

Am really enjoying your detailed presentation of the 40m Soft Rock Lite build. I got my kit and 30m kit a few days ago, but can’t start it for a few weeks due to other commitments. This is my first kit with surface mount. Maybe you can tell us real beginners some of the techniques you are using, like kind of soldering pencil, flux, solder, anti static precautions. I hope your kit works well and, by the time you’re through, have documented all the potential pitfalls.

73, Al, N6ZI