At 12:21 PM 3/22/2006, John Basilotto W5GI wrote:
I'm the one that recommended the 160 hz notch, and I am a broadcast/audio engineer. The short reason for selecting this frequency is that it tends to make the audio sound boomy which is not desirable for amateur work. It is especially troublesome because amateurs use only the bottom 3 KHz of the audio spectrum. You can't compare commercial broadcast EQ preferences with amateur operations simply because we are using different audio spectrums. For additional information regarding audio enhancements for amateur radio, please visit http://www.nu9n.com/tx.html#EQ_Setup
Interesting stuff there.. one quibble I might have is buried down there on Bypass Capacitors:
"For AC power bypassing, use .01µF 2000 Volt ceramic disc capacitors between chassis ground and hot. For grounded or balanced AC, use 2, one between chassis and one side of the AC line, and another between chassis and the other side of the AC line. Make sure that you use 2000 WVDC caps for AC so that there will be no breakdown or excessive heating."
This might make things worse, and is a possible safety hazard, because the capacitors form a leakage path from AC line to chassis. About 250k ohms at 60Hz, or 0.5 mA. It can also lead to some strange things happening if different devices have different amounts of leakage to the different sides of the line, especially if the chassis doesn't have an explicit ground, so the leakage current flows through the shield of an interconnecting cable.
And, of course, if the cap shorts, then you're in real trouble. James Lux, P.E. Spacecraft Radio Frequency Subsystems Group Flight Communications Systems Section Jet Propulsion Laboratory, Mail Stop 161-213 4800 Oak Grove Drive Pasadena CA 91109 tel: (818)354-2075 fax: (818)393-6875
