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BITX40 PTT Noise
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Baruch Atta
Subject:?Re: [BITX20] Re: BITX40 PTT Noise "...It seems that the culprit is the coupling capacitor between microphone amplifier and the?balanced modulator, and the coupling capacitor between receive audio amplifier and the?balanced modulator.? In either transmit or receive mode these capacitors get charged?to a particular value.? When a transition is made from transmit to receive or from receive?to transmit this charge causes a few milliseconds of bias upset in the balanced modulator..." Let me suggest --- has anybody tried --- ?connect a high value resistor between the coupling caps of the mic amp and the receive audio amp.? That should balance the charge on both caps.? Unless it would affect the balanced modulator itself... Any thought on this solution?? Has anyone tried it yet? 73, Joe W3TTT |
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When the microphone amp drives the modulator, it sees the two diodes plus R37,R38,R39. ?A very low impedance load. On Fri, Apr 7, 2017 at 11:42 am, Baruch Atta wrote:
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So the high value resistor will get swamped by that low impedance node when you power up the microphone amp. ?I think. On Fri, Apr 7, 2017 at 12:27 pm, Jerry Gaffke wrote:
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Baruch Atta
So the high value resistor will get swamped by that low impedance node when you power up the microphone amp.? I think. and?? Will it affect the POP? On Fri, Apr 7, 2017 at 3:32 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
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