Timeline for Humming and Transmission issues
Current License: CC BY-SA 3.0
20 events
| when toggle format | what | by | license | comment | |
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| Nov 2, 2012 at 19:25 | comment | added | D.A.S. | The 600ohm line impedance is a North American Standard. It is different elsewhere in the world and in Germany they use a reactive network impedance for load matching. YOu need to start with these basics, then choose an appropriate Hybrid transformer and loading circuit to isolate Rx Tx signals and improve CM rejection. Tweaking your mis-matched design wont help much you understand why it is noisy. | |
| Nov 2, 2012 at 12:18 | comment | added | D.A.S. | Does connecting PC ground cause the noise with no speaker connection? | |
| Nov 2, 2012 at 11:15 | comment | added | Donatus Orth | @Kaz We are working on small details here that do not work together. I want you to draw, yes draw not just describe, a circuit that helps me achieve the goals I described. Thank you in advance. | |
| Nov 2, 2012 at 10:49 | comment | added | Donatus Orth | @Richman Interfacing to my phone's handset does not solve the humming when plugged in to the computer's speaker alone. | |
| Nov 2, 2012 at 10:47 | comment | added | Donatus Orth | @Richman I want you to draw a circuit that shows how to modify my current circuit to work properly. I do not want to read a new term in every other reply you write that makes it even more challenging to understand what you are talking about. If you know your stuff, Richman, you can draw it. Oh and don't draw "black boxes" like "here goes the amplifier". Thank you. | |
| Nov 2, 2012 at 4:37 | comment | added | D.A.S. | The random noise is so bad, I am not sure if any of this design can be salvaged. The dial tone, fundamental hum was less than the random broadband noise. Common mode rejection and 600 ohm impedance matching are key elements of a good telephony interface design which this one lacks. A good design should have noise at -60dBmv and start with a proper hybrid Xfmr. Why not modify/interface to a working phone? | |
| Nov 2, 2012 at 1:26 | history | edited | Donatus Orth | CC BY-SA 3.0 |
added 60 characters in body
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| Nov 2, 2012 at 1:20 | history | edited | Donatus Orth | CC BY-SA 3.0 |
added 60 characters in body
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| Nov 1, 2012 at 22:40 | history | edited | Donatus Orth | CC BY-SA 3.0 |
added 592 characters in body
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| Oct 31, 2012 at 20:28 | answer | added | Kaz | timeline score: 2 | |
| Oct 31, 2012 at 18:29 | history | edited | Donatus Orth | CC BY-SA 3.0 |
added 18 characters in body
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| Oct 31, 2012 at 18:23 | answer | added | D.A.S. | timeline score: 0 | |
| Oct 31, 2012 at 18:22 | comment | added | Donatus Orth | I updated it and answered all your questions there. | |
| Oct 31, 2012 at 18:21 | history | edited | Donatus Orth | CC BY-SA 3.0 |
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| Oct 31, 2012 at 18:08 | comment | added | gbarry | Is the hum in the phone, or in the PC? | |
| Oct 31, 2012 at 17:56 | comment | added | Kaz | "PC Speaker" actually refers to the headphone or line output jack of your computer, is that correct? | |
| Oct 31, 2012 at 17:52 | comment | added | Kaz | Please include power supply details in your schematic. What exactly is GND? Are the op-amps on a dual voltage supply? | |
| Oct 31, 2012 at 16:29 | review | First posts | |||
| Oct 31, 2012 at 20:54 | |||||
| Oct 31, 2012 at 16:20 | history | edited | m.Alin | CC BY-SA 3.0 |
inlined link & schematic
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| Oct 31, 2012 at 16:14 | history | asked | Donatus Orth | CC BY-SA 3.0 |