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I’m in!

Or let me put it this way:

- in traditional FM, you shift the carrier frequency by some amount proportional to the (instantaneous) amplitude of the audio signal
- in EER, you have to shift the carrier frequency exactly by the instataneous frequency of the audio signal, _not_ the amplitude

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Karlis YL3JG

If there's anything critical here, it's that S1 and S2 into that FST3253 give symmetric signals.
So if you feel inclined to worry about something, make sure the S1 and S2 windings
are wound equally tight, with equally long leads going into the board.

So long as C1 can peak the received signal, I would not worry about how close to half-meshed it is.

Jerry

Jerry, I can't see how the varactor FM method might work, as you need precise frequency control. With I2C writes, you control the PLL and thus you have precise control. With varactor, you don't.?

The reason is how the EER method works. So if you're transmitting a 1 kHz tone USB on 10.000 MHz, you are actually putting a 10.001 MHz carrier in the air. You need to shift the frequency by exactly 1 kHz from the reference to get that. The maths in Guido's code take audio input and generate a complex analytic signal from it (basically generate the 90 degrees shifted version). From that representation you can get something called the instantaneous frequency of the audio signal. Which is pretty much the same as converting a 2d vector (complex value) into its polar form (angle and length). The angle (or rather the speed of change) is sent to Si5351 as the FM part, and the length is sent to the envelope shaper (AM).

The instantaneous frequency is exactly the amount of frequency shift that is sent to the Si5351. It has to be exact. In case of 1 tone signal it is the frequency of the audio signal. You can have an offset error, which will just shift the SSB signal, but you can't have a scale error or nonlinearity here. Varactors have pretty much uncalibrated, nonlinear and varying response (e.g., temperature).

--
Karlis YL3JG

Hi Rob

Interesting, it was essentially a fault at same place in the signal path as?L1 connects directly the the antenna socket.
Might be a useful reference for future troubleshooters trawling the forum archive.

Very happy you managed to get your set functioning.


73s Ted
M7ECH

Fully meshed C1 would seem to indicate too low inductance on S3. Removing turns is the wrong way to go.?
Are you sure C5 is correct value? I.e. not too small?
--
> I finally got it all together...now I can't remember where I put it<

VY 73,
Wes

AE6ZM

Sierra Vista, AZ

?

Jerry makes a good point. S3 is the reasonant circuit with C1. If the C1 plates are around half mesh when peaked the turn count and inductance are correct. Primary, S1& S2 windings work simply in tramsformer mode, a turns-per-volt situation. S1 & S2 need enough turns to provide adequate signal level to the IQ Detector, and need to be of equal level. S1 determines the input signal level from the ant to the tuned circuit. So, turns count on S3 is inductance-critical, the rest are turns-critical.
--
> I finally got it all together...now I can't remember where I put it<

VY 73,
Wes

AE6ZM

Sierra Vista, AZ

?

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That's it! I knew I had to be doing something wrong, just a case of knowing what it is. Tnx Bob, Andy, for helping me out.

Brian VE7JKZ

Allison,

> Some of you speculation is about how the si5351 works and much is not given away.??

Yup, the si5351 is poorly documented.
It takes a little bit of reading between the lines and experimentation to figure out what it really does.

On the other hand, it is a $1 part meant mostly to replace a few fixed frequency crystal oscillators.
Using their ClockBuilderPro software to cook up the magic numbers, doing that is well documented.
Building an EER type radio with it is not well documented.


> All you need to test the signal generation is a raduino.?

At which point you get a somewhat intelligible SSB signal with a lot of artifacts.
Those artifacts due to lack of modulation will hide any artifacts due to i2c write delays.?
So hardly seems a conclusive test of i2c writes to the si5351.

> Then you have the overriding thing that moving 8bits via SPI even at 800khz takes about 11us.

Indeed.? Hence my thoughts of using some other method than i2c writes to vary the frequency.

> Putting a varactor on the crystal would create FM, you don't want that.?

The si5351 output clock will vary in frequency, just as it does using your i2c writes.?
I want that.? Even if you choose to call it FM.

> You would have to process the mic input to?a D/A output and then your guessing on frequency as its in the analog realm.?

It the response in frequency to voltage on the varactor diode is non-linear.?
If I were to pursue this, it would be using a lookup table mapping control voltage to the measured deviation.
(Or piece=wise linear interpolation.)

> then the output of the 5351 will multiply that (crystal to VCO then divide to output frequency).?

I'm well aware that if I will get 100x the deviation at 700mhz on the VCO (expressed in Hz), as I will get at 7mhz.

> On a good day that would be band limited.

Yes, I did acknowledge that deviation won't be sufficient using the varactor diode.

> The use of a mixer, really?
> Mix the 5351 and I presume audio, then a crystal filter as you have both sidebands.

You totally missed the point.
With +/- 240ppm deviation using the Si5351b VCXO pin, we don't get enough deviation for direct synthesis on 80m.
(However it should be sufficient for synthesis on 40m and above.)
So for 80m, we would need to create the desired square wave out of the si5351b at 7mhz or higher,?
then translate that square wave down to 80m, apply it to the class C,D,E amp, and modulate the amp.

If the Si5351b were not available so cheaply, I'd consider using the varactor diode to create a square wave
at VHF (where I can get a large deviation, expressed in Hz), then down convert that square wave to HF.
But much easier to just use the VCXO pin on the si5351b.


Given the lack of previous success with this, my impression is that i2c writes and PWM modulation
is not going to get us to a clean signal.?
Better to throw $10 worth of parts at this (16 bit DAC's, Si5351b, buck mode switcher),
and work on algorithms without dealing with the serious handicap of marginal hardware.

Best to start out at 0dBm or so and a nice linear modulator (as you are doing) till it works properly.
Then go to a buck mode switcher for the modulator, it should probably be switching at 1mhz or more
to minimize response time.? Hacking the ebay cheapies to make them programmable might not cut it.

Jerry, KE7ER

With many thousands of QCX transceivers on the air, should we consider a QCX QSO party?? We can have band specific awards, power maximum awards (not all QCX transceivers have the same output), and maybe key awards (internal straight key vs. external SK vs. bug vs. keyer).

Not sure the best month, but I suggest a? transition month between NA and EU seasons so that we can allow those with lowband and highband QCX transceivers equal opportunity to participate.

Just a thought.
--
Harv
K2PI
Warrenton, VA

I've completed a 40M QCX (built the 20M last year). Doing the BPF alignment, I could only get max signal with C1 nearly fully meshed (at a power of 10), so I removed 5 turns from T1 (which was easier than I thought). However I still get the same issue. A power of 10 seems way higher than others I've seen, and I wonder if I should stop messing with it and just continue, or if there is something with C1? Through one complete turn of C1, the scale moves several bars, but never leaves the 10 scale (it was this way prior to removing the turns as well).

Bill
KA3BMU

I'm very curious how well the i2c writes into the si5351 do.
Looking forward to your notes on how clean you can get the signal.<<

Jerry,

All you need to test the signal generation is a raduino.? There are a few things to be aaware of as its clocked at 25mhz
and the there is no amp after it but the code after matching the LCD lines runs.? Of? Encoder, An Uno or nano and a 5351 board.

Some of you speculation is about how the si5351 works and much is not given away.? The PLL VCO is controlled
by the PLL divider or multisynth and the VCO tracks that.? The VCO based on my PLL work should settle fast but
you have some long counter chains and that is a factor.? Then you have the overriding thing that moving 8bits via SPI
even at 800khz takes about 11us.? That last item is the fastest you can change any parameter of the 5351, 1 byte 11us.

Putting a varactor on the crystal would create FM, you don't want that.? You would have to process the mic input to
a D/A output and then your guessing on frequency as its in the analog realm.? then the output of the 5351 will multiply
that (crystal to VCO then divide to output frequency).? On a good day that would be band limited.

The use of a mixer, really?? Mix the 5351 and I presume audio, then a crystal filter as you have both sidebands.
Again that is a ground up bog standard filter SSB.? The EER part could be added but if you get the phasing
wrong the sideband spurs will give a IMD of terrible.

Allison

I agree with Bob.?
Andy
--
The universe is made up of Protons, Neutrons, Electrons but contains only one M0RON.

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5. If I keep pressing the Menu key I go through the rest of the menus until 'Press right button'. So I press the right button and it returns to Step 1 above........

Stop pressing buttons at that point (do not press the left button to go back into the menu), and try the Morse key ... I think you will find the U3S will transmit on 7.018 MHz? ? One thing for sure, the U3S will not transmit anything while in the menu mode.

GL and 73, Bob? ZL1RS

Is it better add or subtract a winding in order to get a more accurate inductance measurement?.

Al,

If your inductance meter is accurate wind it for inductance.
That should give first-time results but still be prepared to adjust turns, correct operation is what you aim for.

73 Alan G4ZFQ

Actually I take that back. L1-L4 I wound based on their inductance value. I wound T1 based on the number of turns.?

Curt M.

I wound mine based on the specified inductance value and didn’t have any problems. I’m sure more people wound thiers based on the number of turns and everything probably worked out fine for them also.?

Curt M.

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Hi Andy,

Yes I did try that, to no avail. Now I'm going to give a step by step of events switching on from a cold start. This may be somewhat lengthy but hopefully there will be a clue somewhere.

1. Power on U3S. Get the welcome screen then it starts tracking the satellites, giving lat/long etc.

2. Press Menu button and see:
0]-4-001,838,100
WSPR---------23-0

I'd think C1 has enough range to tune the winding it is in parallel with.
Otherwise, if anything is critical, it might be the ratios between the various turn counts.
So just build it to the specified number of turns.