Lrl from Italy

[Rubin]

Hello Franco
You write:
We cannot use an oscilloscope for measurements in the sensor stage and for the adjustment need only one voltmeter is required to connect to the output of the filter R16, C18 without the use of the oscillator.
If we have 2-4volts DC output, this means that the sensor stage is working properly without oscillations.
But .... we can have oscillation, because a voltmeter can not show it and let us have an output in the range 2-4v DC
My question.
Can we use the oscilloscope to properly adjust the trimmer on the TR3 emitter or is it practically setting in the field?
Please explain more
Thank you

[FrancoItaly]

Originally Posted by Rubin

Hello Franco
You write:
We cannot use an oscilloscope for measurements in the sensor stage and for the adjustment need only one voltmeter is required to connect to the output of the filter R16, C18 without the use of the oscillator.
If we have 2-4volts DC output, this means that the sensor stage is working properly without oscillations.
But .... we can have oscillation, because a voltmeter can not show it and let us have an output in the range 2-4v DC
My question.
Can we use the oscilloscope to properly adjust the trimmer on the TR3 emitter or is it practically setting in the field?
Please explain more
Thank you

in the helps I wrote: "For the first test do not connect quartz then look at out point, the DC voltage must be 0V.". The sensor stage output is always a DC voltage, rectified by the two diodes. This voltage is the rectified 8Mhz signal. The use of the oscilloscope is only for verifying the proper functioning of the oscillator. Outdoors there is no need for any adjustment other than the threshold and gain in the stage display.

[Rubin]

Thanks for your quick reply.
After checking I saw that. With the trimmer calibration min-max in the emitter TR3 the output to the filter is not 0V DC (without oscillator), but output is 50mv-150mv. So i think we cannot have 0V DC because the diodes produce this increase signal
Ofcourse (without oscillator, coil and antenna) if we touch the input, the output is >8V DC. This is correct?
I repeat again i use only sensor stage without oscillator coil and antenna

[FrancoItaly]

Originally Posted by Rubin

Thanks for your quick reply.
After checking I saw that. With the trimmer calibration min-max in the emitter TR3 the output to the filter is not 0V DC (without oscillator), but output is 50mv-150mv. So i think we cannot have 0V DC because the diodes produce this increase signal
Ofcourse (without oscillator, coil and antenna) if we touch the input, the output is >8V DC. This is correct?
I repeat again i use only sensor stage without oscillator coil and antenna

No, the out sensor stage must be 0V DC, if this is not the case it means that there is still self oscillation, indeed even with 0V volts there could still be a small signal due to the voltage threshold caused by the diodes. In addition, the antenna (even a piece of wire) must be connected because it contributes to the possible self oscillation.

[Rubin]

Hi Franko

If we have an oscillation in sensor stage output (8MHZ disconnect , coil and antenna are connect) at any value C13,C14 >50pf can we remove one capacitor C13 or C14 or all of them?

[FrancoItaly]

Originally Posted by Rubin

Hi Franko

If we have an oscillation in sensor stage output (8MHZ disconnect , coil and antenna are connect) at any value C13,C14 >50pf can we remove one capacitor C13 or C14 or all of them?

Yes, or you can increase R10 / R12 (1.5K or 2.2K)

[Rubin]

Originally Posted by FrancoItaly

Yes, or you can increase R10 / R12 (1.5K or 2.2K)

I think I don't explain it correctly.
I keep as your last update the same values for R10 = 1K trimmer, R2 = 220R and "play" with capacitors values for 0V DC output.
I saw with capacitors <50pf or without capacitors the output is stability and OV DC
It is enough .. or it is necessary to use capacitors?