Threshold Pot doesn't work

[h9361]

I think you will need to replace the 3904 with a 3819 and put it in parallel with Q2.

Thank you.
Is the attached true?
Do you think the pins S and D of Q17 is correct?

[Carl-NC]

Remove D20 & R75. Q17 is OK.

[h9361]

Remove D20 & R75. Q17 is OK.

Thank you.
Dear Carl, i want to design PCB of IDX pro (two tones).
So, i checked Mr. Walter's two tones PCB. He used the Red diode and it is connected to U2in12.
Do you think i need to put it on my PCB?
Another question, a friend recommended me to add a 680K resistor (red 680). Do you think it is better to add it?

[Carl-NC]

Without a lot of study I can't be sure of how that circuit works, so I can't offer any feedback.

[h9361]

Without a lot of study I can't be sure of how that circuit works, so I can't offer any feedback.

Thanks.

[h9361]

Without a lot of study I can't be sure of how that circuit works, so I can't offer any feedback.

Hello dear carl
I have a basic question about resonance frequency.
I read your book and you only pointed to multi frequency only via a overall diagram. I have a request, for better understanding.
Please see attached, there is a coil(L1) and i want to connect it simultaneously to two TANK capacitors (C1 and C2).
Consider following
L1 = 1mH
C1= 10n
C2= 22n
As a result,
L1 + C1= 35khz
L1 + C2 = 23khz
My question is, do you think this connection can simultaneously receive both 35 and 23 khz?

[nejdet]

Hello dear carl
I have a basic question about resonance frequency.
I read your book and you only pointed to multi frequency only via a overall diagram. I have a request, for better understanding.
Please see attached, there is a coil(L1) and i want to connect it simultaneously to two TANK capacitors (C1 and C2).
Consider following
L1 = 1mH
C1= 10n
C2= 22n
As a result,
L1 + C1= 35khz
L1 + C2 = 23khz
My question is, do you think this connection can simultaneously receive both 35 and 23 khz?

The answer is: neither one nor the other frequency. The two capacitors are connected in parallel, therefore the resonant frequency is different!

[h9361]

The answer is: neither one nor the other frequency. The two capacitors are connected in parallel, therefore the resonant frequency is different!

Thanks.
Do you have any simple solution for using two frequency as simultaneously in the schematic?

[h9361]

Dear carl
Is it possible to help me about post #606?
Can you help me how i can use a coil with two different tank capacitors for receiving two different frequencies simultaneously?

[h9361]

Without a lot of study I can't be sure of how that circuit works, so I can't offer any feedback.

Without a lot of study I can't be sure of how that circuit works, so I can't offer any feedback.

Dear carl
Is it possible to help me about post #606?
Can you help me how i can use a coil with two different tank capacitors for receiving two different frequencies simultaneously?

[Carl-NC]

Sorry, I have no idea. ITMD2 and ITMD3 present two different squegging oscillators which effectively run at two frequencies, but they are gated oscillators and that is not what you want. I suggest you ask on a general electronics forum. My personal favorites are

allaboutcircuits.com
electronics.stackexchange.com
electro-tech-online.com

[h9361]

Sorry, I have no idea. ITMD2 and ITMD3 present two different squegging oscillators which effectively run at two frequencies, but they are gated oscillators and that is not what you want. I suggest you ask on a general electronics forum. My personal favorites are

allaboutcircuits.com
electronics.stackexchange.com
electro-tech-online.com

Thanks.
I had a talk, some suggested me coupling mode.
F1=L1+C1
F2=(L1+L2)+C2
This model can receive two frequencies Simultaneously.
Is it possible to tell me your opinion?
Thanks.

[pito]

[h9361]

what are the frequencies ?

KHz range,
exp, 30 and 70Khz.

[Carl-NC]

This model can receive two frequencies Simultaneously.
Is it possible to tell me your opinion?

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.