Lrl from Italy

[JHERICKU]

Hi there Jeg do you pcb on the sensorof 8mhz?can u share?I built the display and the two leds lights when I turn on theswitch..Is it normal? even I turn the potentio meter there isno changes at all..I wish to measure the output of the display stage with multimeter..which pin of IC to check?Thank u in advance..

[Jeg]

Originally Posted by JHERICKU

Hi there Jeg do you pcb on the sensorof 8mhz?can u share?I built the display and the two leds lights when I turn on theswitch..Is it normal? even I turn the potentio meter there isno changes at all..I wish to measure the output of the display stage with multimeter..which pin of IC to check?Thank u in advance..

My friend, i never use ready pcb drawings as i do it for experimentation. I usally make them in ready test pcb boards like in the pic.



i used the circuit of 20MHz drawing with the trimmers.



No its not normal. You should be able to adjust your output so to light just the first led.
You have two pots for the device. One for the differential amplifier and one for the gain. The first one is the most important. Personally i have omitted the gain pot and i fixed my device to the maximum gain which is something like 6 times. The first pot will take your output down to minimum levels so only one led will light.

[JHERICKU]

waht do u think is better?8 mhz or 20? did you also use double face pcb on 8mhz version?I think I will back again from the start..any way this display pcb I used..

[JHERICKU]

I dont know who owns this pcb on display..I
This isthe one I have used but when I turn on the switch..the two leds lights continuously even I turn the potentiometer..Can any one help me..Thanks..

[JHERICKU]

hello Ealk man Can I used value of crystal aside from 20mhz?Is it ok for 16,10 or is it only for 20mhz?thank u in advance..

[Jeg]

prototype pcb board with copper plates isolating oscillator

[Jeg]

Originally Posted by JHERICKU

waht do u think is better?8 mhz or 20? did you also use double face pcb on 8mhz version?I think I will back again from the start..any way this display pcb I used..

The circuits are essentially the same. I went with the 20MHz one as it also has trimmers for adjusting gain. I used 16MHz

Output of sensor before diff 4,5-5,5V

[JHERICKU]

Originally Posted by walkman

For those who want to try.
Enjoy it.

hello friend walkman,BC...c type transistors are not available in our locality..Can I use Bc...b type with this 20mhz design?What can u suggest if I will put the circuit on an aluminum box?does it affect its sensitivity?Also if I do mot have available 20mhz crystal,What value can I use?Did u manage to remove self oscillation?Thank u in advance..

[FrancoItaly]

Originally Posted by JHERICKU

I dont know who owns this pcb on display..I
This isthe one I have used but when I turn on the switch..the two leds lights continuously even I turn the potentiometer..Can any one help me..Thanks..

I am attaching the new display stage again, however if the sensor stage output is too high, the threshold cannot be adjusted, so it is necessary to decrease it.

[JHERICKU]

Originally Posted by walkman

Hi friend,
Please read Francoıtaly 110.page #2732 in message; 20mhz component and help files

I used for frcanco 8mhz aluminum box.Very stable.

My youtube channel videos

https://www.youtube.com/channel/UCG3...I_lXauQ/videos

Good Luck.

Thank u friend walkman for the response..I only have bc...b type transistor..do u think I can make it successfull with with the 8mhz? also can I use different value of potentiometer?Does it affect the performance of the circuit?

[JHERICKU]

Originally Posted by Jeg

prototype pcb board with copper plates isolating oscillator

hi Jeg..Very nice output..what value of variable capacitor and potentiometer did u use?is that the 20mhz version or 8?.I was thinking I will use the pcb of walkman but I will try 4mhz crystal for the meantime until I can find 20mhz and change it..What can u suggest?

[Jeg]

Originally Posted by JHERICKU

hi Jeg..Very nice output..what value of variable capacitor and potentiometer did u use?is that the 20mhz version or 8?.I was thinking I will use the pcb of walkman but I will try 4mhz crystal for the meantime until I can find 20mhz and change it..What can u suggest?

Hey Jh
Franco have said that 20Mhz crystal brings instability. I used a 16MHz one.
Capacitor is something between 4-120pF. It is the common cap that we use in radio receivers.

ps. Attached is the differential i used. The minimum voltage that you can achieve at the output is 1.3V. Your first led starts lighting at 2V. (Approximate values)

[JHERICKU]

Thank you jeg for the response..I will try ur display with volt meter..

[JHERICKU]

Originally Posted by Jeg

prototype pcb board with copper plates isolating oscillator

Hi there Jeg..I cannot see any ic in ur prototype..Did u not not use any IC?Is that the display only?

[Jeg]

It is on a second board my friend and i used an lf353 opamp. I ll find some time to take a pic from inside.

[FrancoItaly]

Originally Posted by Jeg

It is on a second board my friend and i used an lf353 opamp. I ll find some time to take a pic from inside.

lf353 op amp is not suitable because it must be powered with split voltage, it takes the LM358.

[Jeg]

Thanks Franco.
Due to the fact that both of its inputs are positive, i don't really see any malfunction other than i can't take the output to zero level. But i'll test 358 to see the difference.

[Jeg]

Franco, have you ever tried to use a second vertical antenna for emission? There must be a way to increase the distance of research. In a next build, instead of connecting oscillator to the input antenna, i'll feed the input through a second vertical antenna coupling. I am very curious!

[Jeg]

I tested lm358 and now the output of diff can go down to zero. Thanks Franco

JH the inside boards. The pink one is a dc to dc boost converter for 2.5 euros. It takes the 3,7V of the battery to 16V and then i drive with that my regulators.

[FrancoItaly]

Originally Posted by Jeg

I tested lm358 and now the output of diff can go down to zero. Thanks Franco

JH the inside boards. The pink one is a dc to dc boost converter for 2.5 euros. It takes the 3,7V of the battery to 16V and then i drive with that my regulators.

The DC / DC converter generates disturbances, since it is in practice an oscillator, in high gain circuits it can be a problem, I suggest to use 2 batteries in series of 9 V, since the absorption is a few tens of mA.

[Jeg]

Originally Posted by FrancoItaly

The DC / DC converter generates disturbances, since it is in practice an oscillator, in high gain circuits it can be a problem, I suggest to use 2 batteries in series of 9 V, since the absorption is a few tens of mA.

Nice point thank you. Thankfully in this case i don't experience any interference from converter. Probably due to the aluminum box which is grounded and the distance from receiver transistors. Next time i will encase it in a faraday shield.

ps. with this battery i can work at least ten hours before charging while it also powers this led voltmeter which is a demanding load.

[kaveh]

Hello everyone and Mr. Franco. Mr. Franco, I am using a 14.7456 MHz crystal. How do I know what a good harmonic setting is for the c10 capacitor? When I turn the c10 trimmer, the output voltage of the sensor reaches its maximum in one place and the lowest in another. Where is the good harmonic?

[JHERICKU]

Anyone has the pcb of sensor stage from 8mhz..?The one that is ready to print but only the sensor stage..Thank u in advance..

[JHERICKU]

I have here already the sensor stage circuit but the problem is some labels are not readable..it was overlayed by the lines..Foes anyone have a better circuit?Thank u..

[Jeg]

Hey Jh
Print the circuit and the board drawing and compare them to find out the components. If you have problems then put in a red circle what you need to know, and help will arrive.
ps. Why don't you use the other circuit with the trimmers?