Gentlemen,

I have looked at a number of schematics but do not seem to find the one matching the current Bitx40 R3 transciever being sent from India.

Could someone please point me in the right direction or send a link to the correct file(s)

Tnx,

PJH, N7PXY

No Raduino here, but do have a Nano to play with. ?Here's a code scrap to replace that final clause in doTuning() to give the tuning pot a bit of hysterisis. ?Perhaps somebody could try it out.

  // the tuning knob is at neither extremities, tune the signals as usual
  else if (knob != old_knob){
    static char dir_knob;
    if ( (knob>old_knob) && ((dir_knob==1) || ((knob-old_knob) >5)) ||
         (knob<old_knob) && ((dir_knob==0) || ((old_knob-knob) >5)) )   {
       if (knob>old_knob) {
            dir_knob=1;
            frequency = baseTune + (50l * (knob-5));
       } else {
            dir_knob=0;
            frequency = baseTune + (50l * knob);
       }
       old_knob = knob;
       setFrequency(frequency);
       updateDisplay();
    }
o
   tone(CW_TONE, sideTone);
   tone(6, 1000);

Also, if you want a 1000hz square wave on pin 6 as a test signal, just execute this line somewhere:

? ? tone(6,1000);

That sets up a counter-timer to continuously generate the square wave while the Nano goes off and does other things.

Shut it down with

? ? noTone();

Jerry, KE7ER

Thanks very much for this, John.

For the record and/or posterity, I was unable to get a full 1A from HF Sigs' board #869.

I turned both R136 and RV1 fully clockwise, then opened RV1 until the Fluke 87 showed 100mA. ?(Amp input; meter on the A/mA setting)

R136 had to rotate almost fully CCW to get a solid 7W output power on the WM-2 Wattmeter. ?The PA was only drawing about 740mA at that point.

The IRF510's heatsink was warm to the touch, and the resting current draw was up to about 150mA. ?I turned RV1 a bit CW so the 'warm' current was 100 mA. ?Current with a strong 'ahhh' and a solid 7W out still shows about 740mA draw by the PA.

I'll have a CARE package from Mouser tomorrow - I'll get the signal on the o-scope on the dummy load and check the output signal then. ?In the mean time, I have a solid, intelligible signal on the SDR receiver now - thanks for that!

开云体育

Has anyone succeeded with adding CW properly? I have seen several possibilities on here, but no working examples. If yes, how did you do it? Or is it just impractical, like making milk from chalk and water? I was planning to at least inject a tone from a simple circuit for antenna tuning. But I took down my friends G5RV jr. in favor of a better 40 meter only dipole. No tuner needed for either end of the band. A 20 watt BITX CW signal could be a lot more successful than my MFJ-9240 CW transceiver which is about 6-7 watts, and works great for QRP. ??

I am sure a narrow audio filter switched in, would be helpful for focusing on a signal. But how do you put a signal smack on the tuned frequency without rebuilding the whole thing?

On a side note, I used my tablet to generate a 1khz tone, and held the mic to the tablet speaker to check the SWR while adjusting the antenna tuner. Worked great when I had that other antenna up.

Just a couple of bits plus Allisons suggestions although this applies more to the homebrew variety.

Tips n Mods
--
Rob G4NQX

That's a broadband transformer. ?Either core should work fine, and they likely use what they got.

Moving from the Schottky Bat54s back to the two non-schottky 1n4148's would require more drive, not less. ? Near as I can tell, those Bat54s diodes were a problem for W5KUB and for nobody else. ?Allison is referring to the diode ring mixer at D10,11,12,13, and I'm pretty sure is mostly concerned about receiving.

In post?/g/BITX20/message/22042? I gave my rather uninformed take on proper local oscillator injection level into that diode ring, suggesting 7dbm was appropriate for the 1n4148's. ?I can easily believe that 7dbm is appropriate for schottky diodes like the Bat54 but that the 1n4148's require significantly more drive. ?I have no idea how much drive they are currently getting, or how much they should get. ?If the 1n4148's are not getting driven hard enough, might be worth trying a couple Bat54s in that diode ring. ?Properly driven, the 1n4148's might give a larger dynamic range, though most of us wouldn't notice.

Allison mentions impedance matching at the diode ring as also being important, especially where the diode ring sends a signal into that IF amp at Q2 on receive. ?If Q2 presents 200 ohms to the mixer, then the amp at Q1 will see that same 200 ohms when driving the mixer. ?Allison suggests the mixer would perform better in a 50 ohm environment. ?Then higher drive from the local oscillator into the diode ring becomes more important, those diodes will need sufficient current to get them into a lower impedance part of their IR curve. ?Not obvious to me we care about matching impedances into the local oscillator port, I'd think the Si5351 3v pk-pk square wave through a series resistor and dc blocking cap might be sufficient.

Jerry, KE7ER

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