Lrl from Italy

[edward]

Hi mr franco and thank you for your help

I tested bc548, bc547 b , bc 238b , bc 547c , and the results was same, my pcb is self oscillation, i have to use 20 pf capacitors for c13 , c14 to avoid from self oscilation
I think when i increase total value of c2 , c3 , c4 for increasing output voltage the lrl sensivity decreases


Now i have 2 question mr franco
1- how much is maximum amount that can be used for r10 and r12
2- does your lrl dont work with low voltage in output? ( for example 0.5 volts or 0.6 volts)

Hi mr franco

There is something interesting

When i use switching power supply the output voltage increases from 3 volts to 6 volts( without quartz)
I think this is because of long wire of switching power supply
The last test was with 2× 9 volts battery
I think self ocsilating has another reason
Before that i made your lrl sensor with your pcb layout and the results was same i had 3 volts in output without quartz
Both pcb was double side
What about the tr4 collector? how much should this voltage be?

[edward]

1 -Usually it is chosen for R10 / R12 a value lower than that of R9 / R13. I made several copies of my lrl and I always managed to eliminate self oscillation. Try to remove C13 / C14, in this way it should stop oscillating, if so, decrease R10 / R12 until it oscillates again, then increase again R10 / R12 until the oscillations cease. For example R10 / R12 = 1 K no oscillations, R10 / R12 = 680 ohms no oscillations ... R10 / R12 = 220 ohms no oscillations, R10 / R12 = 100 ohms yes oscillations, choose R10 / R12 = 220 ohms. This difficulty in eliminating self oscillations makes me think of a defect in the pcb, there may be some parasitic coupling. I always recommend using a double-sided pcb.
2 - my lrl works also with low voltage output but for me it's better at least 2V, in fact it could happen when the installation was completed or in the field that the tension lowered further, in this way it would also greatly reduce the sensitivity, since it could not regulate the threshold effectively.

I removed c13 , c14 and i had 6 volts in output without quartz
R10 , R12 was 1 k resistors i chenged these with 2× 5k potentiometers and i started to increasing the potentiometers in 4k for both output voltage were 0 volt

I have 8 volts in tr4 collector

[FrancoItaly]

I removed c13 , c14 and i had 6 volts in output without quartz
R10 , R12 was 1 k resistors i chenged these with 2× 5k potentiometers and i started to increasing the potentiometers in 4k for both output voltage were 0 volt

I have 8 volts in tr4 collector

Well, 6V in output it's ok. The only unknown is if the gain is sufficient, however the further gain of the antenna amplifier should compensate.

[edward]

1 -Usually it is chosen for R10 / R12 a value lower than that of R9 / R13. I made several copies of my lrl and I always managed to eliminate self oscillation. Try to remove C13 / C14, in this way it should stop oscillating, if so, decrease R10 / R12 until it oscillates again, then increase again R10 / R12 until the oscillations cease. For example R10 / R12 = 1 K no oscillations, R10 / R12 = 680 ohms no oscillations ... R10 / R12 = 220 ohms no oscillations, R10 / R12 = 100 ohms yes oscillations, choose R10 / R12 = 220 ohms. This difficulty in eliminating self oscillations makes me think of a defect in the pcb, there may be some parasitic coupling. I always recommend using a double-sided pcb.
2 - my lrl works also with low voltage output but for me it's better at least 2V, in fact it could happen when the installation was completed or in the field that the tension lowered further, in this way it would also greatly reduce the sensitivity, since it could not regulate the threshold effectively.

I conected the quartz and out put voltage is 0 volt

C13 , c14 removed
R10 , r12 4 kilo ohm
Quartz connected output voltage is 0 volt
Quartz disconnected out put voltage is 0 volt
Tr1 emitter frequency is 8 mega heartz
Tr4 collector voltage is 8 volt

And I am tired

[FrancoItaly]

Hi mr franco

There is something interesting

When i use a the output voltage increases from 3 volts to 6 volts( without quartz)
I think this is because of long wire of switching power supply
The last test was with 2× 9 volts battery
I think self ocsilating has another reason
Before that i made your lrl sensor with your pcb layout and the results was same i had 3 volts in output without quartz
Both pcb was double side
What about the tr4 collector? how much should this voltage be?

switching power supply is not recommended. May be in the laboratory there are other forms of disturbance, you have to try outside with battery power. It is not possible to measure the signal on the collector of TR4 with an oscilloscope because the signal disappears, the DC output measurement is sufficient. Also try to keep the antenna very short, 10 -15cm, inside the laboratory.

[FrancoItaly]

I conected the quartz and out put voltage is 0 volt

C13 , c14 removed
R10 , r12 4 kilo ohm
Quartz connected output voltage is 0 volt
Quartz disconnected out put voltage is 0 volt
Tr1 emitter frequency is 8 mega heartz
Tr4 collector voltage is 8 volt

And I am tired

DC voltage of TR4 collector must be about 5-6V but with R10=1K, by changing R10 also collector voltage changes. You have =0V with quartz because the gain is very poor, try C2 only (disconnect C3/C4) you have 1pF, if you have no result try 2pf or more.

[edward]

switching power supply is not recommended. May be in the laboratory there are other forms of disturbance, you have to try outside with battery power. It is not possible to measure the signal on the collector of TR4 with an oscilloscope because the signal disappears, the DC output measurement is sufficient. Also try to keep the antenna very short, 10 -15cm, inside the laboratory.

Yes mr franco i was thinking this is for laboratory i think the test should be outside the laboratory

[FrancoItaly]

Yes mr franco i was thinking this is for laboratory i think the test should be outside the laboratory

When I said that the measurement could not be performed with the scope I meant the 8MHz signal. Tell me the measurements of your sensor stage pcb, have you connected the lower part to the ground?

[edward]

When I said that the measurement could not be performed with the scope I meant the 8MHz signal. Tell me the measurements of your sensor stage pcb, have you connected the lower part to the ground?

Yes the lower part was connected to ground

[edward]

DC voltage of TR4 collector must be about 5-6V but with R10=1K, by changing R10 also collector voltage changes. You have =0V with quartz because the gain is very poor, try C2 only (disconnect C3/C4) you have 1pF, if you have no result try 2pf or more.

But if the laboratory is the reason this means when the lrl approaches the phenomenon the sensor start to self oscilating??

[FrancoItaly]

But if the laboratory is the reason this means when the lrl approaches the phenomenon the sensor start to self oscilating??

No, the lrl is also very sensible to many electromagnetic disturbances, also in my lab I have many signals.

[edward]

No, the lrl is also very sensible to many electromagnetic disturbances, also in my lab I have many signals.

In my laboratory there is laptop , wireless modem , swithching powersupply , osciloscope , near the pcb when i am testing and on the left and right sides of my laboratory there is tow stores with same instruments

[FrancoItaly]

In my laboratory there is laptop , wireless modem , swithching powersupply , osciloscope , near the pcb when i am testing and on the left and right sides of my laboratory there is tow stores with same instruments

sources of disturbance can be even a few meters away. Several years ago I was in an area with TV repeaters, in that place the lrl was practically unusable for a radius of at least 100m. The input circuit, L1 / C10, is tuned around 100Mhz, any transmitter on that frequency, or superior harmonic or sub harmonic, can generate a signal in the lrl.

[edward]

sources of disturbance can be even a few meters away. Several years ago I was in an area with TV repeaters, in that place the lrl was practically unusable for a radius of at least 100m. The input circuit, L1 / C10, is tuned around 100Mhz, any transmitter on that frequency, or superior harmonic or sub harmonic, can generate a signal in the lrl.

I tested the circuit in another place and the results was same

I have 7 volts in my output without quartz and c13 , c14 560pf
C2 , c3 , c4 = 1 pf r10 , r12 =1k
Does your lrl work with this state and without quartz? I have 6 to 7 volts in my aoutput and when i touch the antenna the voltage decreases about 200 milivolts

[FrancoItaly]

I tested the circuit in another place and the results was same

I have 7 volts in my output without quartz and c13 , c14 560pf
C2 , c3 , c4 = 1 pf r10 , r12 =1k
Does your lrl work with this state and without quartz? I have 6 to 7 volts in my aoutput and when i touch the antenna the voltage decreases about 200 milivolts

Yes, my lrl also works this way, in fact this lrl originated from an RF sniffer that self oscillated, later I wanted to create a lrl simpler to set up. I realized that the self-oscillation was due to the characteristics of the pcb.