The Mighty "Fisher CZ5 Quicksilver" and it's secrets

[dbanner]

I see also on schematic of cz6, after the notch filter, there is op amp with a 10k trimmer designated as comp X alignment. What is the purpose? It only varies the gain of this stage?

[ivconic]

The notch is tuned to 14.5kHz ... and it's in the 15kHz channel. Does that make any sense?

Those are the hand draws from my late friend JD.
He was neat and precise in what he did, yet is possible that he made mistake in a draw.
And maybe not.
I can't tell for sure, i never was interested that much in CZ circuitry, except for just few minor details.
So Q. you could be right.
And maybe not.

[dbanner]

CZ 6. Notch is in the 5khz channel.

[Carl-NC]

CZ 6. Notch is in the 5khz channel.

Correct, it's in the LF channel.

I see also on schematic of cz6, after the notch filter, there is op amp with a 10k trimmer designated as comp X alignment. What is the purpose? It only varies the gain of this stage?

The CZs do GB by subtracting the reactive & resistive signals in the harmonic and fundamental channels to produce composite reactive and resistive signals. The 10k trimmer is for composite-reactive alignment.

[Qiaozhi]

Correct, it's in the LF channel.

That what I would have expected. It must be a labeling problem in the hand-drawn schematic.

[dbanner]

This looks familiar. Resemblance to crocodile teeth. I saw it on Russian forum.

[Altra]

I made a timing diagram for 3khz and 15khz, which I believe to be correct. Not sure how this type of Tx signal is calculated? I can see how the pattern relates to the fundamental frequency. But how is the 28uS, 50uS, 11uS etc, determined?

Trying first to program this into the 8bit pic micro using assembly language. Next, I will try using output compare modules in a pic32 or dspic33. It would be interesting if anybody can make an Arduino output these signals or the original CZ 5khz and 15khz.

[Carl-NC]

But how is the 28uS, 50uS, 11uS etc, determined?

Most likely experimentally.

[Skippy]

Quote:"I can see how the pattern relates to the fundamental frequency. But how is the 28uS, 50uS, 11uS etc, determined?"
I'm sure it's just duty-cycle modulation. The high freq ( 5f ) is modulated with the low freq ( f ) such that the extremes of the low-freq sine wave give ( for example ) 90:10 and 10:90 duty-cycle, and the zero-crossing of f gives a 50:50 waveform at 5f.

I'll have a go at spectrum-analysing the Whites f/5f waveform, to see what the relative levels are. And I'll try and recreate a f/3f waveform to analyse similarly.

[Skippy]

Here's my best analysis of the Whites 3kHz / 15kHz waveform:
For a raw signal of amplitude +5V / -5V, my spectrum analyser shows:
3 kHz amplitude = 4.7V peak ( 3.32V RMS )
15 kHz amplitude = 6.72V peak ( 4.75V RMS )
that is a ratio of 1 to 1.43 .

[Altra]

Thanks for the replies.

Skippy your spectrum chart shows that the fifth(15khz) is much stronger than the 3rd (9khz).


The patent I posted in #42. Has a formula (fig4) for I(wrt), maybe this could be converted to voltage to derive the spwm?

[dbanner]

1:3 system where f=5khz > 200uS. 3f=15khz

I propose intervals of 45uS and 10uS configuration of pulse train like shown in poor sketch.
Where A=45uS and B=10uS.

So 45-10-45-45-10-45

Have no clue how to simulate. But goal is to boost 3rd harmonic while suppression others

[dbanner]

It seems to me that this is current ramping.

There is highest current peak which is the fundamental with a period of 200uS.

There are two lesser peaks giving a total of three peaks in 200uS period, 200/3=66.6uS which is 15khz, there's your third harmonic.

[Altra]

1:3 system where f=5khz > 200uS. 3f=15khz

I propose intervals of 45uS and 10uS configuration of pulse train like shown in poor sketch.
Where A=45uS and B=10uS.

So 45-10-45-45-10-45

Have no clue how to simulate. But goal is to boost 3rd harmonic while suppression others

Interesting, maybe Skippy can run your series on his simulator.

The 1:5 seems to be ideal for dual frequency which Carl suggested and Skippy confirmed.

@ Skippy, what would the 5th harmonic look like if we used a simple 3khz square wave for tx, instead of the complex wave form?

Thanks

[Skippy]

"What would the 5th harmonic look like if we used a simple 3kHz square wave for TX ?"
The third harmonic has amplitude = 0.333 relative to the fundamental; the fifth harmonic has amplitude = 0.200 relative to fundamental.

For a theoretical 'CZ' square wave that was amplitude +10 Volts / -10 Volts , the amplitude of the sine wave constituents is:
Fundamental = 12.73 V (9.0 V RMS)
3rd harm = 4.24 V (3.0 V RMS)
5th harm = 2.55 V (1.8 V RMS)