From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Sent: Saturday, December 30, 2006 3:33 PM To: [email protected] Subject: [Repeater-Builder] Re: audio equalizers for repeater audio
-Ok just out of mere curiosity what about for audio that is too bassy? Happy New Year NB2A Tom Tom ~ To change the roll off with less bass, increase the size of the series resistor for more highs, although you will increase the loss through the circuit. If you can handle the loss (peak to peak audio goes down when the series resistor gets bigger), I like that approach. You can change the .2 uf capacitor to a .1 (point 1), but for me, the roll off isn't as steep, and the overall lows are missing. It sounds kind of "tinny". It doesn't have the full audio low end spectrum. Running the audio through a service monitor shows a "weak" low end frequency response. I've run audio curves on the service monitor through receivers, taking audio from the discriminator/detector, time after time. For a simple two component fix, which is all that was discussed here, this provides the best time constant / roll off / de-emphasis for me. I use it on all GE (MVP, Exec II, MII) and Motorola (Micor, Mitrek), Vertex (5000, 7000, 9000), and it is always the same. I can talk into two different receivers on the mountain top, one GE and one Motorola, both with the same capacitor and resistor (.2 to ground, followed by a 15K resistor), and you won't be able to tell a difference. They both sound the same. Both use a Micor squelch gate, so you can't tell listening to the squelch tail either. There will be many other comments about Time Constants, better values, and op amps with feed back settings, but this is the best set of components that I have found over years of linking multiple repeaters together, trying to maintain the integrity of the audio from site to site, without getting crazy about 18 repeaters in a row that have to have flat audio. Flat Audio is a whole different discussion. This was just about de-emphasis and two components, and how I chose to de-emphasize radios, of all manufacturers. Right or wrong, I make it my standard. The nice thing about standards is that there are so many to choose from! Bill Hudson W6CBS
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