[Elecraft] KPA1500 Fan Noise - Not An Issue

[Jim Brown]

On 6/4/2018 8:34 AM, Bob McGraw K4TAX wrote:
> Room acoustics play a big part of the "how loud" factor. Absorptive 
> materials applied to the walls an ceiling of a room, specially small 
> rooms,  do reduce the build up of sound / noise emitted from fans and 
> blowers.

YES! This is excellent advice. Indeed, the first place to put absorptive 
material is on wall surfaces around the amp, treating other wall 
surfaces can also help a lot. Hard surfaces contain the sound, causing 
it to bounce around the room. Soft surfaces absorb the sound, causing it 
to die out more quickly.

Mechanical coupling of vibration to the desk increases the audibility of 
noise, so it can also help to isolate the amp from the shelf it is 
sitting on.

Fan noise on the transmitted signal can be minimized in several ways, 
all of which are pretty simple.

First, keep the mic close to your mouth -- sound falls off by 6dB per 
doubling of distance. Boom mics, like the CM500, are great for this. For 
best sound quality, I try to keep the mic an inch or two above and to 
the side of my mouth. The principle is to maximize speech and minimize 
noise -- a simple signal to noise problem.

Second, don't turn mic gain up higher than needed, and don't overdo 
compression. This is the primary cause of excessive noise on transmitted 
signals.

Third, set TXEQ to emphasize the speech range and de-emphasize other 
sound. My guideline EQ settings do this -- max cut of the three lower 
bands, 6 dB cut of the fourth band (400 Hz), and then get reports from a 
careful listener.

73, Jim K9YC