RELIC HAWK

[o.mag]

hi mike
I understand why you changed only the load side negative (positive being powered by the battery) but for tested the oscillator I changed both and the distortion appear on both sides. a higher current for IC does not really help anything
The schemat of post 949 please me well. but I have problems for the simulation. I look for the mistakes I make

olivier

[bernte_one]

hello all here

where can i find last pcb files of relic hawk?

many thanks

[Davor]

IMHO every oscillator that is running near saturation, supplied with well stabilised and low noise voltage supply will perform very well. The only difference comes from the oscillator design, and if it is symmetrical like push-pull - it will do very well.

When you look at it, every amplitude stabilisation circuitry works the same way voltage stabilisation would do, and that's the whole point.

You can always make a PI regulator that will push the oscillator transistor deeper into C class as amplitude rises. Its stability and noise will depend solely upon the power supply.

[mikebg]

Distortion of negative half-wave (shown with green arrows). To avoid this, we should use center tapped TX coil and full wave rectifiers.
I will show the analysis of this when I have time for our hobby.

Here it is:

[mikebg]

Hi Olivier,
I analysed your idea in post #943 to use Vee rail for supply rest part of RX.
For this purpose I increased 4 times current from Vee source (placing 500 ohm resistor instead 2k).
To see collector curent of Q2, hold pressed Shift + click on collector lead.
The attached image shows two drawbacks:
1. Low efficiency of pumping pulse. We should decrease resistance of R1 until B=2A or conducting angle of Q2 decreases to 120 deg.
2. Distortion of negative half-wave (shown with green arrows). To avoid this, we should use center tapped TX coil and full wave rectifiers.
I will show the analysis of this when I have time for our hobby.

[o.mag]

hi mike
Yes i can you open with CircuitMaker the compressed file attached in post # 941
but I did not have time to fully understand

olivier

?

Hi Olivier,
Can you open with CircuitMaker the compressed file attached in post # 941 ?

[mikebg]

Hi Olivier,
Can you open with CircuitMaker the compressed file attached in post # 941 ?

[o.mag]

hi mike

OK : like this ! (the head is the red box )

olivier

[mikebg]

hi mike
a remark
in this diagram the ground is connected to the - terminal of the battery.
Ground use for the RX preamp.
do you want creates a negative voltage supplied to the other OPA ?

olivier

No, Olivier.
I think the TX has no enough power to supply increased looad because the negative rectified voltage is formed in half-wave when Q2 is not conducting.
As I mentioned in post #937, my idea is to supply only U2 (the RX preamp placed inside search head).

[o.mag]

hi mike
a remark
in this diagram the ground is connected to the - terminal of the battery.
Ground use for the RX preamp.
do you want creates a negative voltage supplied to the other OPA ?

olivier

[WM6]

I have no time to make it for simulation with LTspice.
Mike

It would be interesting to see filter characteristic of those rectifier.

[mikebg]

Hi Olivier.
I made TX circuit of post # 937 for SPICE analysis by you with CircuitMaker 2000. It is attached here in compressed format. I have no time to make it for simulation with LTspice.
Mike

[o.mag]

hello mikebg

you right, you can cancel service Q3 (which I do not understand the utility)
see post 929

olivier

[porkluvr]

Thank you. Whether right or wrong, your lectures are always fun and entertaining.

[mikebg]

Mike, you should remove the components in the red box. Unless I am mistaken, the 68k resistor was put there to isolate an oscilloscope lead during setup. One end is a test point.

The net segment that you labeled "Test" is connected to ground which means that 0V=test in your simulation.

Right click the net, and then "Highlight Net" and you will see what I mean.

Porkluvr, in my not humble opinion, you are mistaken
Please click on emitter of Q1 to see voltage signal. The result is shown below. There is nothing interesting for measurement with oscope. Only a competent radio amateur will say that this is an inefficient TX circuit because the conducting angle of an amplifier class C is more than 180 deg.

As a redesigner of this TX circuit, I would connect an oscope to output of U1 because for me, the P.I. controller is the most important thing in this circuit, so it should be tested. The P.I. controller should operate:
a) quick (minimal settling time),
b) with wide change of output voltage Vo (without saturation of U1) and
c) stabile (without oscillation or ringing).

When I connect R10 to ground for a test, amplitude of oscillation increases. The controller senses this and starts to increase output potential Vo of U1 in order to decrease amplitude of oscillation to previous level. The oscope will show this settling process.

When I connect R10 to a positive voltage, amplitude of oscillation decreases. The controller should decrease output potential Vo of U1 in order to increase amplitude of oscillation and we will see on oscope if output saturates. To have very low voltage Vo without saturation, I use LM358 or LM324 instead TL074.

However in practice, to test settling process, I will connect R10 to a pulse generator with very low frequency, for example 2Hz and will see with oscope if the settling process is enough quick and if the controller operates with ringing. SPICE also can simulate this.