At 4/16/2007 10:00 PM, you wrote: >Good thinking Bob, I will look in to it. Do you have a schematic or >the model number of the squelch you were working with?
No schematic handy here. It was the stock squelch circuit in a mid-80's vintage Hamtronics R144 or whatever "repeater grade" RX they were selling at the time. The noise filter was a simple 2-pole BPF with a very high Q. The op amp they used was the dedicated op amp within the MC3357 or MC3359 IF amp/detector-on-a-chip. Nothing wrong with the op amp, just the circuit design around it. >I would think ringing would be a problem with passive components Like >L/C filters. But it may exist in a low quality op-amp that is not >designed with a wide bandwidth. In this case the op amp isn't the problem, it's the overall circuit. > I believe the LM324 series is only >rated for 12kHz of bandwidth, the TL084 is about 3MHz. The unity gain BW of the LM324 is 1 MHz; the TL084 is 3 MHz. I wouldn't use either one much above audio frequencies. >I am not even sure if I can simulate impulse noise. But in theory we >can write a software algorithim to look for a patterned pulse and >attempt to compenstate. Any decent SPICE simulator should be able to give you the transient response of your filter. Bob NO6B
