While I certainly lack the deep understanding you guys have, tonight I went ahead and removed c91 and c92. I thought I could jumper over them but now I realize I was mistaken. This had the intended effect, but also one unintended effect. The thing now squeals like crazy at lower volumes! There's some sort of uncontrolled oscillation happening when I lower the volume control. I wish I understood why that was. Any comments about that?

Flipping the offset from - to + works famously, btw. I wish the VFO I'm using let me switch it on just a switch, but it's not as readily programmable as the Raduino. I did just recently pick up an arduino recently though and intended to do some experimenting :)

--
Ryan Flowers KC7RYS?

Alright guys, check it out. I have had a great idea. Start a thread Called "Users User Manual", start it with links?to the official instructions. Additional notes on missing #5, and advice on which way to hold the tuning pot when wiring it up. Then links to stuff like randy compiled on voltage measurements, and signal paths. And additional links and texts people think are most important for newcomers and old timers to know about getting the most you can out of it. The most important thing about it is posting links in place of duplicating data and clogging up the files section. And a "Users User Manual" ?is something people will likely search the messages for and find a whole thread devoted to it. And keep it free, and open source in the spirit of community.

I thought it was too good to keep to myself. You might wonder what Happened to John if I worked quietly on this for a few days. Nah, you'd probably throw a party.

And I think it was an EYE (I) first, then an EL (l) second, and third was a ONE (1). Honest, it was just cut and paste. It was just the number digits I changed for frequency scanning speed, and 5K steps. All those other things were already there, and still are, and some people like it. It really works. I use it every day. I even slowed it down even more by increasing the delay to 275. And whatever comes after it. ?Fuzzball.

So whaddaya think? If anyone else inspired enough to get a good start on it tomorrow. You got my blessing. Hey let's make the Technical Writing Professor Thompson do it. That reference to wiring the tuning pot was for you by the way.

You might need a more solid ground plane. ?Perhaps stitch some of the islands on the backside together using traces on the front side. ?

You are using 1n4148's in the mixers, Farhan is using BAT54 dual shottky diodes. ?The shottky diodes don't need as much drive from the bfo or vfo as the 1n4148's do. ?Also, the two shottky diodes in the balanced modulator are guaranteed to be balanced, not so for two randomly chosen 1n4148's.

Looks like you have a totally different final amplifier. ?Farhan's push-pull IRF510's reduce the second harmonic, your single 2SC1971 may require more output filtering than Farhan's did. ?

Farhan's initial schematic showed lots of BC849's, but only because he didn't have a decal for 2n3904's. ?His current schematic shows 2n3904's.

It looks good! If it were mine I would change tow minor things. The resistors I would show as 4K7 for 4.7 because my old eyes have trouble with those little tiny decimal points any more, and I would leave a bit more copper showing around the mounting holes to make sure the stand offs have a good contact area.

Jeff

N9ARZ

Hi Fellows

This is only a prototype to work with a PCB.

I have the file with the Sprint layout from ABACOM.

Any concern about the design please forward to-Heriberto- cl2kmk@... ??

Qrv's

73's Jc

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Ah, come on. ?You're tougher than that. ?It's how you learn. ?You've learned a fair bit these last couple months.

Now go clean up that wireup documentation.

Jerry

Noel

Used this code - it works great! More reliable and responsive than the original.?

Thanks,

Howard, VK4BS

That's really great Jerry. Thank you. Now be sure you save it somewhere so you can post it again the next time it comes up. Maybe a mini book to point newcomers towards might be a good thing. But......

Now... please tell me if I got the right spot in the code to change it. Or where is "The sketch has been written."?

Jack has traumatised me so very much, with pouncing on the snippets I copy and paste, and the mysterious characters?within. I am too scared to do anything without confirmation. (Shaking)

I don't need to ask anyone else for proof about using USB, I never felt that the contrary needed to be argued.

I am surprised to see the snark. It's new. I saw someone didn't like it and dropped an F-bomb. But I am cool with everyone. As long as they don't get me so flustered I make myself look like an ID10T. Again.?

I am looking forward to checking this out. I concur about the other eyes trying some things seen in the group. I am still thinking about trying a mic gain circuit. Just to try it out.

OK, here is where I am so far. I removed C91 and C92. I changed the 1.05 Raduino sketch by? adding code to read pin D7. In the original sketch, this was reserved for the TX/RX line monitor, which I don't use. You can use pretty much any other unused Arduino pin if you want. You also need to got through the code and remove references to that particular pin. Make sure you save your sketch under a new filename so as not to lose the original!!!

In the "setup" area, I made sure that pin D7 had the pullup enabled: pinMode(ULSB_SELECT,INPUT_PULLUP); (I #defined D7 as ULSB_SELECT previously)

Then, I added this code in the "loop" function:

if (digitalRead(ULSB_SELECT) == 1) /* if U/LSB switch is high, do LSB,
?if low, do USB */
{
? if (isUSB ==1)
? {
? isUSB = 0;
? setFrequency(frequency);
? updateDisplay();
? }
}
else
{
? if (isUSB == 0)
? {
? isUSB =1;
? setFrequency(frequency);
? updateDisplay();
? }
}

Finally, the little trick that allowed the displayed frequency to be correct for both LSB and USB: I modified this line in the setFrequency() function:

? if (isUSB){
??? si5351.set_freq((bfo_freq + f - 3100) * 100ULL, SI5351_CLK2);

The addition is the "- 3100" after the "freq + f". This keeps the displayed frequency the same, but shifts the actual VFO frequency to put the passband in the right spot.

Now - the caveat! I didn't have any definitive way to test this, as right now, I hear nothing on 7.076 (JT65 freq for 40m), even on the "big" radio. However, I took off the antenna connection of the bitx40, set my IC-718 to the lowest output I could, keyed it up in 7.150 MHz AM, and then tuned up & down from there on the bitx while trying both modes. In either mode, the frequency shift and volume of the received signal seemed to be pretty much the same, as I tuned up & down from the "center" frequency, certainly it should be pretty darned close! Hopefully, I'll see if I can hear some signals later & confirm the operation was a success!

John Smith,

Here's your paper.

Assume for now that we are transmitting an AM signal at 12.000mhz with a 1khz tone from the microphone. ?The two diode modulator get's a 12.000mhz carrier from the BFO and mixes that with the 0.001mhz audio from the microphone. ? The modulator gives us a signal consisting of the carrier, the carrier plus the audio or 12.001mhz and the carrier minus the audio or 11.999mhz. ?If we send that straight out to the IRF510, that's AM phone on 12mhz.

For LSB, all we want is the 11.999mhz signal. ?We ?can get that by having ?very sharp bandpass filter (the crystal filter) that allows through the 11.999mhz modulator product but not the 12.000mhz or 12.001mhz components. ?Sending that on to the IRF510 would give an LSB signal at 12.000 MHz. ?(The number you read on the dial is the frequency of the suppressed carrier.)

For USB, all we want is the 12.001mhz signal. ?We ?can get that by having ?very sharp bandpass filter that allows through the 12.001mhz modulator product but not the 12.000mhz or 11.999mhz components. ?Sending that on to the IRF510 would give a USB signal at 12.000 MHz.

It's really hard to move the crystal filter. ?Easier to build the crystal filter for only 12.000mhz, and place the BFO at either 11.999mhz (for USB) or 12.001mhz (for LSB).

If we speak into the microphone, most of us give more than just a 1khz tone, there's a range of audio frequencies of interest for intelligible speech from around 500hz to 3000hz. ? ?So that crystal filter must allow a band of frequencies about 2500hz wide through, not just a single frequency. The Bitx40 has a balanced modulator, so the carrier is mostly suppressed. ?It's good enough if the crystal filter does a good enough job of knocking out the far sideband, which starts at 500+500=1000hz away from the low audio frequencies that we are trying to transmit.

We want to transmit at 7mhz, not 12mhz. ?The diode ring mixer combines the above 12mhz sideband signal with the VFO. ?If the VFO is at 5mhz, then the 7mhz bandpass filter (the three torroids L1,L2,L3) will allow through the 7mhz difference signal from 12mhz-5mhz. ?If the VFO is at 19mhz, then the bandpass filter will allow through the 7mhz difference of 19mhz-12mhz. ?Note that 19-12.001 = 6.999mhz, so in the 19mhz case what was 12mhz USB has become 7mhz LSB.

The sketch has been written. ?Several here are successfully using a 19mhz VFO to transmit 40m USB. ?Ask them. ? Only physical change is to remove C91 and C92, the Raduino doesn't need them for 5mhz or 19mhz. ?Pete is successfully using the alternate method of moving the BFO from the Si5351.

Don't take personally my attempts at guiding this conversation in the direction of physical reality. ?I don't want 1000 lurkers coming away with the wrong idea of what works. ?I will occasionally try correct wrong information. ? Some may find me a bit snarky at times, that's my attempt at humor. ? Some may find you a bit snarky too.

> I would have expected you to ...

Tough. ?(See, I can be kind of snarky.)

Jerry, KE7ER

I never said anyone proposed it. But I am now saying it has come up several times. After the earliest conversations of operating CW, on this BITX someone had looked it up and provided greater detail on it. And now we know we can't, and why we can't.

Now for a serious request of you Jerry. Between several to many times you have offered your opinion of running the VFO at 19Mhz instead of 5Mhz. But I don't recall you ever detailing how to do it. You know I can follow along and change the code. But what else is involved. Any other specific changes? As much as you seem to think it would solve a lot of problems and make some hacking easier. I would have expected you to have written a paper, or constantly instruct people how to do it, or upload a sketch with it all done for us by now.?

Is this where the VFO get's set at 19Mhz? This is just a cut and paste.

#define INIT_BFO_FREQ (1199800L)

unsigned long baseTune = ?7100000L;

unsigned long bfo_freq = 11998000L;

Finally, I think your ragging on me for being wrong now is because I said the toroid band pass filter put's it on LSB. But it's the crystal filter that does that. Right? I would rather be corrected and learn, than get a blow up about it later. Or continue the same debate without ever making progress. We are licenced communicators. We can do better.

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