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The birdie at 7.2mhz is due to the 5'th harmonic of the vfo at 5*(12-7.2)=24mhz
beating with the 2'ed harmonic of the bfo at 2*12=24mhz.

Allard's v2 firmware drives the BFO from the si5351,
so can keep vfo up around 19.2mhz while still being able to select USB or LSB.
He moves the bfo down a few khz to below the crystal filter when operating USB with a high side vfo.
? ??

Oddly enough, the 5'th harmonic of the vfo at 5*(12+7.2)=96mhz
now beats with the 8'th harmonic of the bfo at 8*12=96mhz.
So we still have a (much weaker) birdie when receiving 7.2mhz.


On Thu, Jan 11, 2018 at 08:56 pm, Dale Brooks KG7SSB wrote:

Ashhar, I'm having trouble with the good 'ole birdie at 7.199 mhz on my home brew bitx40 designed radio. I had the same problem with the hf sig board but was able to get rid of it by placing a tuned circuit on the output of the VFO Raduino board. Not so lucky with this one. Do you have any ideas that I can try to solve this problem? And is there an easy way to shift the VFO frequency (Raduino)? so that I'm above the IF frequency instead of below it. I'm sure this would get rid of the problem.Thanks for the help,,,Dale kg7ssb..

Very exciting!? We are looking forward to the shake down testing outcome.

Mike ZL1AXG

On Fri, 12 Jan 2018 at 7:03 PM, Diver Martin <diver.martin@...> wrote:

I like the SSM2167 for one big reason: Simpler package.? While QFN is easy to do in a mass-production environment and I've never even had a problem with my hot air station, I hate QFN's/ TDFN' (Tiny Damned Frickin No-leaded packages) when doing prototyping or small quantity stuff.??

For the first run of this PCB, I'm sure there will be problems, and being able to probe the pins directly is always nice.? It's an extra dollar in low quantities, but the compression part is nice. I added it to my design, made a few changes, so I should be pretty good to go with this first revision.

That said, in my many many years of making circuit boards, I have had a design work and fit_exactly_ as intended and specified only once in my life.? It was quite the celebration!? With this particular system, I'm sure there will be no exceptions to my rule that there's always a revB :)

Changes:

Moved mic/speaker output headers outwards by 0.2" to make front panel mating better

Added SSM2167 mic amplifier, variable resistor for gain, adds speech compression (1:1 to 1:10)

Other features not stated earlier, S-meter and SWR measurement.

Here we goooo......

On Thu, Jan 11, 2018 at 8:24 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

The MAX9814 could work well
But be aware that while the AGC will reduce gain when your audio level gets too high,
it will also increase gain when there is nothing but background noise.
So during pauses in speech, your friends will be impressed by the sound of the
apparently monstrous cooling fan required to cool the mighty uBitx.?

Might be worth looking at the SSM2167
? ??
You can disable the speech compression feature if that's not what you want.
Still provides AGC style gain reduction when audio levels get too high,
and also reduces gain when audio levels are too low.

Jerry, KE7ER



On Thu, Jan 11, 2018 at 07:51 am, Michael Hagen wrote:

I used the MAX 9814, follow the datasheet suggestions. Set the final output with a pot.

?

--

Martin Held - AE7EU

-------------------------------------------------------------------------------
If there aren't any questions, then what is there to learn?

I like the SSM2167 for one big reason: Simpler package.? While QFN is easy to do in a mass-production environment and I've never even had a problem with my hot air station, I hate QFN's/ TDFN' (Tiny Damned Frickin No-leaded packages) when doing prototyping or small quantity stuff.??

For the first run of this PCB, I'm sure there will be problems, and being able to probe the pins directly is always nice.? It's an extra dollar in low quantities, but the compression part is nice. I added it to my design, made a few changes, so I should be pretty good to go with this first revision.

That said, in my many many years of making circuit boards, I have had a design work and fit_exactly_ as intended and specified only once in my life.? It was quite the celebration!? With this particular system, I'm sure there will be no exceptions to my rule that there's always a revB :)

Changes:

Moved mic/speaker output headers outwards by 0.2" to make front panel mating better

Added SSM2167 mic amplifier, variable resistor for gain, adds speech compression (1:1 to 1:10)

Other features not stated earlier, S-meter and SWR measurement.

Here we goooo......

On Thu, Jan 11, 2018 at 8:24 AM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

The MAX9814 could work well
But be aware that while the AGC will reduce gain when your audio level gets too high,
it will also increase gain when there is nothing but background noise.
So during pauses in speech, your friends will be impressed by the sound of the
apparently monstrous cooling fan required to cool the mighty uBitx.?

Might be worth looking at the SSM2167
? ??
You can disable the speech compression feature if that's not what you want.
Still provides AGC style gain reduction when audio levels get too high,
and also reduces gain when audio levels are too low.

Jerry, KE7ER



On Thu, Jan 11, 2018 at 07:51 am, Michael Hagen wrote:

I used the MAX 9814, follow the datasheet suggestions. Set the final output with a pot.

?

--

Martin Held - AE7EU

-------------------------------------------------------------------------------
If there aren't any questions, then what is there to learn?

The MAX9814 could work well
But be aware that while the AGC will reduce gain when your audio level gets too high,
it will also increase gain when there is nothing but background noise.
So during pauses in speech, your friends will be impressed by the sound of the
apparently monstrous cooling fan required to cool the mighty uBitx.?

Might be worth looking at the SSM2167
? ??
You can disable the speech compression feature if that's not what you want.
Still provides AGC style gain reduction when audio levels get too high,
and also reduces gain when audio levels are too low.

Jerry, KE7ER



On Thu, Jan 11, 2018 at 07:51 am, Michael Hagen wrote:

I used the MAX 9814, follow the datasheet suggestions. Set the final output with a pot.

?

It can't be anything blown up. Can you measure how much is the current draw on receive? It should be around 150 ma. That is an indicator that things are alright.

- f

On Fri, Jan 12, 2018 at 8:37 AM, Jim Richard <jimk1uqi@...> wrote:

Oops:? After completing my build in a metal cookie box,? transmit was fine with 5 watts to dummy load on 40 meters.? Receive had good rf noise, lots of birdies, but no real signals except for some local AM broadcast stations, which sounded good.? Just using an indoor amplified antenna, but expected more signals. Had a brain f**t put the metal cover on the box to see if that would help the birdies. Forgot to insulate the top of the display board and the nice rf background noise went away.? Shorted something up there!? Switched off and removed cover:? turned on: no rf noise, display is lit, displaying a 40 meter frequency, but nothing happens when turning is turned or pushed.? Suspect oscillator is not sending any signals or the Arduino is not functional, or controlling.? Did not see or smell any magic smoke so maybe it's a relatively minor matter.??

? I'm currently doing Chemotherapy and don't trust myself to troubleshoot further at this time,? probably will get back to it next week.? In the meantime, I'm trying to learn as much about the troubleshooting both the hardware and software, so I can have a logical plan for fixing my radio.? Depending on the helpful savvy people on this fine group to point me in the right direction!? Thanks guys!!!?

Oops:? After completing my build in a metal cookie box,? transmit was fine with 5 watts to dummy load on 40 meters.? Receive had good rf noise, lots of birdies, but no real signals except for some local AM broadcast stations, which sounded good.? Just using an indoor amplified antenna, but expected more signals. Had a brain f**t put the metal cover on the box to see if that would help the birdies. Forgot to insulate the top of the display board and the nice rf background noise went away.? Shorted something up there!? Switched off and removed cover:? turned on: no rf noise, display is lit, displaying a 40 meter frequency, but nothing happens when turning is turned or pushed.? Suspect oscillator is not sending any signals or the Arduino is not functional, or controlling.? Did not see or smell any magic smoke so maybe it's a relatively minor matter.??

? I'm currently doing Chemotherapy and don't trust myself to troubleshoot further at this time,? probably will get back to it next week.? In the meantime, I'm trying to learn as much about the troubleshooting both the hardware and software, so I can have a logical plan for fixing my radio.? Depending on the helpful savvy people on this fine group to point me in the right direction!? Thanks guys!!!?

You are correct, the LFP caps see half of the peak-to-peak voltage, since that RF is centered on ground.

In Farhan's example of 3000 ohms at 10W:
Vrms*Vrms/Ohms = Watts? ? so? ? Vrms = sqrt(Watts * Ohms) = sqrt(3000*10) = 173.2 Volts RMS across the cap
The peak voltage is sqrt(2)=1.414 time the RMS voltage (assuming this is a sine wave halfway through the filter), so 173.2*1.414 = 245 Volts peak to ground.



Hans, on a completely different note, you may find this interesting,
It takes the three si5351 msynth register values for p1, p2, p3 as reported by Clockbuilderpro
and back computes values for a, b, c
Just got it to work this morning, seems right but may yet have issues.

I assume a,b,c must all be integers.
However, a and b could take on fractional values in increments of 1/128 and still yield integer values for p1,p2,p3.
I wonder if that's legal, though not seeing that out of Clockbuilderpro.
Clockbuilderpro seems to do a massive search for the lowest possible integer values of a,b,c in both PLL and output msynth's
when I ask for one output of a particular frequency, often leaving both msynths in fractional mode.
So low integer values are likely the primary way to reduce phase noise.
This is a considerably different approach than all the C code for the si5351 I find out there on the interwebs
Regardless, my guess is that the si5351 has less phase noise in all cases than the typical LC vfo.

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char** argv) {
  int  floorg, floorc, ax128, bx128, a, b, c, p1, p2, p3;

  if (argc==4) {
      p1 = atoi(argv[1]);
      p2 = atoi(argv[2]);
      p3 = atoi(argv[3]);
  } else {
      printf("Usage: Takes 3 int args for si5351 msynth reg values p1,p2,p3\n");
      printf("reports int values for a,b,c where a+b/c is the divide ratio\n");
      exit(1);
  }
  printf("  p1:%d  p2:%d  p3:%d \n", p1, p2, p3);
  c = p3;

  // Given an si5351 msynth divide of (a + b/c):
  // p1 = 128*a + Floor(128*b/c) - 512
  // p2 = 128*b - c*Floor(128*b/c)
  // p3 = c			   // All from Silabs AN619
  // Since b<c, Floor(128*b/c) has a value between 0 and 127 inclusive
  // We compute a and b for each of those values, determine which is legal

  for (floorg=0; floorg<128; floorg++) {	// Guess value of Floor(128*b/c)
      ax128 = p1 + 512 - floorg;		// Where ax128 is a*128
      bx128 = p2 + c*floorg;			//  and bx128 is b*128
      floorc = bx128/c;				// Compute value Floor(128*b/c)
      a = ax128/128;  b=bx128/128;
      // Report result if value of Floor(128*b/c) is consistent with guess,
      // and if the computed values for a and b are integers, and b<c.
      if (floorc==floorg && ax128%128==0 && bx128%128==0 && b<c)
          printf("  a:%d b:%d c:%d \n", a, b, c);
  }
  exit(0);
}

Jerry, KE7ER


On Thu, Jan 11, 2018 at 12:39 pm, Hans Summers wrote:

An interesting question. In the LPF, does the capacitor see the peak-peak voltage? It is connected to ground. So, doesn't that mean it sees the peak voltage (1/2 the peak-peak)?

?

Looks pretty awesome!?

Can I recommend using headers for the Teensy?board (as opposed to directly soldering to the board). It adds a little to the cost, but saves headaches down the road when replacing/upgrading the board :)?
--
David K4DBZ
Unofficial bitx chatroom:?