Here are a couple of simple circuits to do what you want. Use a well filtered source of +V for the audio amplifier to keep from developing some hum on the output. Any voltage source from +5 to +12 should work. Adjust the variable resistor to set the gain of the audio amplifier.
73 - Jim W5ZIT --- On Mon, 7/13/09, John Transue <[email protected]> wrote: From: John Transue <[email protected]> Subject: [Repeater-Builder] Need circuit -- COS Sense & AF Amplify [1 Attachment] To: [email protected] Date: Monday, July 13, 2009, 8:42 AM [Attachment(s) from John Transue included below] I need to interface a link receiver (Icom F221S) with an ACC RC-850. This presents two problems. First, the Icom receiver uses active low COS, and the RC-850 doesn't seem to have a means to select the sense of a link receiver. The repeater receiver (Midland BaseTech II) uses active high COS. Second, the discriminator audio output from the Icom is about 0.6 Vp-p, but the RC-850 hardware manual says the audio input should be between 1 and 5 Vp-p. I have posted the first problem to the ACC group but have received no reply. Yes, the ACC manual says to insert a 47K resistor in a specified place to increase sensitivity. I can do this but it requires I take the repeater out of operation for a day or so. It occurs to me that a circuit to reverse the sense of the COS might be available from this group. Also, a simple amplifier circuit could solve the AF level problem. I know this is all elementary, but I am not competent to design these simple circuits. I will gladly build them. I would appreciate any help you can provide on the design. Thanks. John Transue AF4PD
