Lrl from Italy

[JHERICKU]

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]

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]

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]

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]

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]

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?