Threshold Pot doesn't work

[h9361]

Are you wanting an RX coil that can receive 2 frequencies, or a TX coil that can generate 2 frequencies? What you show cannot oscillate, it has no feedback mechanism. Otherwise, I have no experience trying to do what I think you want to do.

Only receiving RX without any TX.

[Carl-NC]

Any coil can do that as long as you don't resonate it with a cap.

[h9361]

Any coil can do that as long as you don't resonate it with a cap.

I want to receive only two or three frequencies at the same time.
Please see attached, this is named as coupling mode (Tap).



A friend told me old radio used this method.
I have a question, which of the following is true?

Calculation 1
F1=(L1+L2+L3)+C1
F2=(L1+L2)+C2
F3=L1+C3

Or
Calculation 2
F1=(L1+L2+L3)+C1
F2=(L2+L3)+C2
F3=L3+C3

[Carl-NC]

I suspect it's not so simple, and I don't know without either building the circuit or simulating it. But you can do that, so I suggest you put it in LTSpice and find out what happens.

[h9361]

I suspect it's not so simple, and I don't know without either building the circuit or simulating it. But you can do that, so I suggest you put it in LTSpice and find out what happens.

I have not worked with LTSpice. I usually use Porteous software for simulation, i will try to simulate it.
I have a another question. Please see again schematic of #618, do you have any suggestion for making a bandpass filter?
For exp, i want to only receive from 5Khz to 30Khz range. Suppose that we have two coils ( inductor) and two resonance capacitors.
First Tank is tuned to 5Khz and second is tuned to 30Khz. But i do not know how to draw a bandpass for this range via this coils and resonance capacitors.
Thanks

[moodz]

here is a free online tool for desiging LC filters ( low, band, high )

https://markimicrowave.com/technical...r-design-tool/

It can export the design in ltspice so you can sim it.

[nejdet]

Something like this maybe...

[h9361]

I suspect it's not so simple, and I don't know without either building the circuit or simulating it. But you can do that, so I suggest you put it in LTSpice and find out what happens.

Please check attached. Do you think the bandpass (from 15Khz to 107Khz) is true?

[h9361]

here is a free online tool for desiging LC filters ( low, band, high )

https://markimicrowave.com/technical...r-design-tool/

It can export the design in ltspice so you can sim it.

Thanks

[h9361]

Something like this maybe...

thanks

[Carl-NC]

Please check attached. Do you think the bandpass (from 15Khz to 107Khz) is true?

Again, I don't know without simulating it. It will also make a difference whether L3 and L4 are coupled (also polarity) or decoupled.

[eduardo1979]

Hi h9361.
Why don't you try implementing the TX circuit from the Fisher CZ5? I think it would be a good starting point.

[h9361]

Hi h9361.
Why don't you try implementing the TX circuit from the Fisher CZ5? I think it would be a good starting point.

Thanks.
Dear eduardo1979, i want to make a receiver alone, not TX.
Can you send me a link for fisher cz2?
Thanks.

[Carl-NC]

All multifrequency designs I am aware of use a wideband RX coil and either do narrowband filtering in the preamp(s), or with filters after the preamp, or use narrowband demodulators. I don't know of anyone trying to use narrowband RX coils.

[h9361]

Again, I don't know without simulating it. It will also make a difference whether L3 and L4 are coupled (also polarity) or decoupled.

Suppose that L3 and L4 are separated (independent ).
Generally, do you think it is better to be used coupled or decoupled?