At 10/18/2007 14:11, you wrote: >But you have a chicken and egg situation, is it the controllers fault >or the radios? Not all radios have bias and not all controllers charge >caps backwards. You can solve the problem by removing the mic bias >resistor from the radio,
I'd like to do that, but I think I just discovered a difference between the MVP & Mastr II exciter boards: the Mastr II supplies bias via a resistor connected to pin 11 of U101 (audio processing IC), whereas in the MVP there is no resistor - the bias appears to provided internally within the IC. This is a problem because there doesn't appear to be any way to remove the bias. > installing a non-polar cap anywhere in the >audio path I suppose that's the only choice I have, but since there's already a 1 µF cap in the controller, the 2nd series cap needs to be a significantly higher value to avoid the combination of the 2 causing another high pass rolloff. > or replacing the polar cap with a non-polar. Can do that, but then I have a 2nd big ugly leaded cap hanging off the bottom of the SMC board. >Take a look at the schematic I posted earlier, it will suit your needs >but I do not program that well, hence the open source of the hardware. >If there is any intrest I will finish the PCB, which will measure 1.9" >X 2.5" and about 0.5" tall and doesn't use any surface mount >components. I appreciate the effort, but for this task I need a ready-to-go solution. Bob NO6B
