Mathew Quaife wrote: > Bob, I am not all that familiar with op amp's. Do you have a diagram of > something I can try to see if it works. The 1.5 KHz might be enough > allowing the controller to maintain the rest, won't know until it is all > hooked up and running. But in my thinking, 3.0 Khz would be much > better, especially for those of us that are soft spoken. > > Mathew
If you're eventually going into a controller but you don't have it hooked up that way yet, most controllers have PLENTY of amplification in them to handle bringing that level up, and most have a "factory recommended" way of feeding in discriminator audio (basically what Vol Sq/Hi is... it's filtered, but still pre-emphasized) and handling the 6db/octave de-emphasis. You state "The 1.5 KHz might be enough"... remember you're not looking at deviation anymore - the signal's already detected and is just a peak-to-peak AC voltage now at the point of the radio you're looking at... you just need to know if the voltage swing there at Vol Sq/Hi is "enough" for the controller's input circuits. The controller manufacturer will publish (in a good controller manual) the range that an audio input will support, and will have instructions about how to set the audio levels inside the controller and coming back out. Check the controller manual for a section that talks about how to feed the controller with (pre-)emphasized audio. That's basically what Vol Sq/Hi is, from the standpoint of most controller designs. What controller is it? If I'm mistaken about what you're trying to do here, and you're not using a commercial controller, then you'll have to come up with an amplification circuit. Here's a little (ahem...) light... reading... on op-amps, if you're so inclined. Guaranteed to cure insomnia if you struggle with that. http://focus.ti.com/lit/an/sloa058/sloa058.pdf Nate WY0X
