TESORO GOLDEN SABRE

[Max]

Qiaozhi mentioned the coil's series resistance. I have also started adding parallel resistance to help simulate the unknown quantity of cable loss. Adding parallel resistance smooths out the collector voltage hump and also helps tame the FET gate waveform. The AVS (Automatic Voltage Stabilization?) circuit, or whatever it's called, will not work smoothly when the circuit Q is too high - or when too much power is being produced, or even if the frequency fo is raised significantly. I can't fully explain this last statement and don't want to try and elaborate, but you will see what I mean whan you start playing with the supply voltage. (Or maybe it's just ME whose screwed up!) Look for jagged wave on the FET's gate.
When I first started working with the TGS I changed the FET gate's RC components, or else the transmit signal would not stabilize. Now, I leave the original RC circuit values, but keep lowering and lowering the value of parallel coil resistance (simulating circuit parasitic LOSS) until the amplitude stabilizes. I usually must have a value of around 8kΩ or sometimes even less, with fo=14kHz.Trial and error. Hey, I don't know what else to do.... . I never suggested LTspice is perfect, but it's all I got because I do not have a lab!

Max, Ivconic: I see you have discovered that the simulations show a voltage "hump" on the collector. My simulations also show that the collector waveform does not have 50-50 symmetry. You have scope, I believe so, please tell me: how bad is it in real life? It may be an anomally of the software and models used.

Adding parallel resistance on the coil will smooth the hump, but there is still an apparent failure to attain a symmetrical waveform. How bad it is in real life, is what I would like to know. Please measure and tell me.
??
Max I still owe you some reference material. It's coming. Gotta go.

Hi prokluvr,
and really thanks for all the stuff you provided and references to LTspice too.
Me personally found the software really good for our (limited) purposes. I think that it's made good enough to give some answers we await from little mods on original schematic without directly putting on hands on pcb everytime.

I've tested voltage at collector a number of times during tuning of TGS and from what I remember the software give a good approximation of the effects there. And yes there could be instability at osc too depending on many factors. Most important is the feedback circuit, what you call AVS.

The very hi-gain it has could introduce oscillations at low frequency cause of overdamping effect that occours sometimes... you can see it on the diagrams of LTspice too... are like output bursts followed by zero voltage signal... till, after a while, output stabilize. That's cause of the gain... but I guess that also temperature on the real world could give similar effects: fets are well know for changing dinamic params really easy with temp. variations due to the structure they have internally...respect e.g. BJT configuration.

Is it cause of bleeping we are looking for ?

Maybe ! Or maybe, more realistic, is just one cause of erratic bleeping that sometimes occours.

Anyway, thanks again for your help and interest in TGS circuit.

Kind regards,
Max

[Max]

One important thing you have missed out in your schematic - the DC resistance of the coil. At the moment you are using an ideal inductor. You need to include a resistor in series with the inductor, as it will make a difference to the results.

Hi,
actually not. I've used the porkluvr's model that is:

5.8mH inductance
22 ohm series resistance (actually we have a bit more)
25Kohm parallel
950pF capacitance

So we are about ok using it.

Kind regards,
Max

[porkluvr]

Don't forget R parallel, too!

Qiaozhi mentioned the coil's series resistance. I have also started adding parallel resistance to help simulate the unknown quantity of cable loss. Adding parallel resistance smooths out the collector voltage hump and also helps tame the FET gate waveform. The AVS (Automatic Voltage Stabilization?) circuit, or whatever it's called, will not work smoothly when the circuit Q is too high - or when too much power is being produced, or even if the frequency fo is raised significantly. I can't fully explain this last statement and don't want to try and elaborate, but you will see what I mean whan you start playing with the supply voltage. (Or maybe it's just ME whose screwed up!) Look for jagged wave on the FET's gate.
When I first started working with the TGS I changed the FET gate's RC components, or else the transmit signal would not stabilize. Now, I leave the original RC circuit values, but keep lowering and lowering the value of parallel coil resistance (simulating circuit parasitic LOSS) until the amplitude stabilizes. I usually must have a value of around 8kΩ or sometimes even less, with fo=14kHz.Trial and error. Hey, I don't know what else to do.... . I never suggested LTspice is perfect, but it's all I got because I do not have a lab!

Max, Ivconic: I see you have discovered that the simulations show a voltage "hump" on the collector. My simulations also show that the collector waveform does not have 50-50 symmetry. You have scope, I believe so, please tell me: how bad is it in real life? It may be an anomally of the software and models used.

Adding parallel resistance on the coil will smooth the hump, but there is still an apparent failure to attain a symmetrical waveform. How bad it is in real life, is what I would like to know. Please measure and tell me.
??
Max I still owe you some reference material. It's coming. Gotta go.

[ivconic]

Good point....i'll try later...
Now i am in the middle of something else....be back..

[Qiaozhi]

One important thing you have missed out in your schematic - the DC resistance of the coil. At the moment you are using an ideal inductor. You need to include a resistor in series with the inductor, as it will make a difference to the results.

[Max]

1N750 is actually 4V7 so zener is not problem here...

Hi,
yes is the feedback circuit of TGS osc that makes output be almost not dependant from supply variations up the a certain level (depending on zener voltage and diode forward drop).

That's cool cause you can program e.g. double voltage accross coil just changing the zener and the regulator!

I think there's enough to test with some spare zener and look for results.

Kind regards,
Max

[Max]

1N750 is actually 4V7 so zener is not problem here...

Hi,
yes it's ok. I've repeated your test using +8 and then changed to +9... and it goes well.

You have to close the diagram window and make again Simulation->Run so it will recalculate the points of transient a. again with right params.

Otherwise it will be not so happy of changes.

Another thing to keep in mind is that labels mean nothing here and could be confusing also.

Best regards,
Max

[ivconic]

1N750 is actually 4V7 so zener is not problem here...

[ivconic]

Huh! Again error. Now i am more sure it has bugs....Look;
I took previous oscillator schematic with 8v supply and othe zener...
Just changed 8v to 9v and look what i got!?
Now, on this, when i repeat it changes scope amplitude to 16v...???
OK no big deal. I'll remember this thing and each time i need accurate scope i'll repeat those steps twice to be sure...until find out what is the problem?

...

[Max]

Hi,
that's what I mean: you get about 16Vpp output (60% more than original) just changing 7808 with 7809 and the zener with an 8.2 one.

Kind regards,
Max

[ivconic]

Hi,
very nice picture. 7809 will be fine too... you'll get something less 18Vpp but it's ok for testing a bit more power I think... you'll notice for sure an increase in the max sensitive area at center of coil for far targets.

I saw the picture... but you have to consider also that you'll have problems using the 15V zener with so low supply... cause of the lack of stabilization...

I suggest to change also the zener for something e.g. 8.2V (or disable the amplitude feeback of fet circuit).

What do you think ?

Best regards,
Max

Huh! I missed that!
Now is all clear! Damn! I am still novice here....

[ivconic]

And repeated again at it gave 16v amplitude...???
This software has bugs! I am sure!
I repeated few times...
Bug occurs only first time you change power supply...for example previous 12v changed to 9v gave false at scope. When repeated again, clicking on 9v and changed to 9 again...aplitude shown on scope is now 16v...!?!?!?

Either bug either i missed something?

[Max]

Very nice coil Max!
Yes you are right...low drop. Or i can use 7809 instead with lower amplitude at output. I dont need really much stronger output at all. This one works just fine. I just wanted to experiment a bit more...
SnagIt is installed, here is shot from LTSpice...showing 10v supply and 18v amplitude..

Hi,
very nice picture. 7809 will be fine too... you'll get something less 18Vpp but it's ok for testing a bit more power I think... you'll notice for sure an increase in the max sensitive area at center of coil for far targets.

I saw the picture... but you have to consider also that you'll have problems using the 15V zener with so low supply... cause of the lack of stabilization...

I suggest to change also the zener for something e.g. 8.2V (or disable the amplitude feeback of fet circuit).

What do you think ?

Best regards,
Max

[ivconic]

I just checked; 9v supply gives 11v aplitude..!?? Such a difference???
10 volts gave 18v and 9volts only 11v amplitude...??? Is this possible?

[ivconic]

Very nice coil Max!
Yes you are right...low drop. Or i can use 7809 instead with lower amplitude at output. I dont need really much stronger output at all. This one works just fine. I just wanted to experiment a bit more...
SnagIt is installed, here is shot from LTSpice...showing 10v supply and 18v amplitude..