IMPROVING THE AUDIO QUALITY OF YOUR STATION - PART 4

In the last few articles we have considered most of the controls on the modern receiver as well as the audio amplification.

There are three more controls that you can use. The Noise Blanker, Auto Notch Filter (ANF or BC) and Digital Signal Processor (DSP).

The Noise Blanker may be adjustable on some radios, others are not. This feature will work best on man made noises. Ignitions and pulses that are not fast. If your noise has a detectable frequency to it, the Noise Blanker can do a good job of taking it out. Especially if your NB is adjustable. It can be adjusted to the

speed of your interference and many times take it right out.

The Auto Notch Filter or Beat Cancel will do a good job of removing a carrier produced by an AM Broadcast Station or some lid tuning up on you. This feature works quite well and allows you to operate in the vicinity of a commercial AM station.

The Digital Signal processor is no doubt the most sophisticated of the Noise reduction tools.

What does it do digitally, I have no idea. However what it does to the analog signal you are listening to is quite interesting.

If you look at atmospheric noise on an oscilloscope, it will look like a bunch of sharp spikes on a slow scan. However, taking a closer look, by speeding the sweep of the scope, these spikes are really smooth sine waves of different frequencies. Lots of them.

Measuring the frequency with a counter will give you about a 1,800 Hz reading. This is right in the middle of the audio spectrum of about 300 to 3,000 Hz. No wonder it blast our ears off.

When you turn the DSP on, with a little adjustment, you will see several of these sine waves removed. You can vary this with the DSP control. When you read the counter, it will go from 1,800 Hz to anywhere from 200 to 600 Hz. Quite a reduction in noise. However, it is adjustable because some of the reduction will affect the signal you are listening to.

Be sure to look for noises you produce in your home. One of the biggest culprits is the switching power supplies used in many other electronic devices (wall warts). LED lights, florescent lights, power savers, dimmer switches, WIFI routers, cordless phones, tablets and on and on.

We live in a noisy world, but at least we can try and do something about it.

73,

Ralph WD0EJA