The Swezey Digital Filter

Frequency Asked Questions (FAQ's)

What is the Demonstration Version of the program?

The Demonstration Version is intended to allow interested people to try the program before purchasing it. It is free for anyone to use but is crippled by a periodic buzzing sound.

I have a small portable short wave radio, can I still use the program with it?

Yes and No. the program doesn't care what the audio input source is and will filter it. Unfortunately, most PC's give off so much radio frequency noise that you probably can't pick up any thing when your receiver is near your computer.

Is this program useful for Amateur ("Ham") Radio Operators?

Yes and No. The processing delays make two way voice communications too awkward to do but the program is fine for just copying signals.

The program is heavily optimized for enhancing voice and musical broadcast signals and NOT for pre-filtering high speed digital formats such as RTTY or FAX. The mathematical methods employed tend to smear those signals.

The program may be useful for CW reception owing to the extremely narrow passband filtering it can do.

This program was not originally intended for Ham radio use.

When I start the program my computer slows down.

The program is doing an enormous number of calculations to carry out the filtering. As more and more features are selected the program will eventually start to 'chug' (i.e. stop-start-stop-start).

If you are using file input to file output no data is lost and this is only an inconvenience but if you are using the filter in real time it will miss input data.

To run faster turn off unnecessary features, choose a slower sample rate or a smaller FFT size.

Why is the "Filtered Output" delayed behind the "Unfiltered Input"?

The "Unfiltered Input" is the original signal coming from your receiver, the "Filtered Output" is coming out of the program. The delay is necessary to buffer the audio to be able to process it. I have tried to keep it as short as possible but buffering is needed to maintain a smooth output stream. I usually select "Unfiltered Input" while tuning and then switch to "Filtered Output" once I have selected a station to listen to.

After I run the program all the sound in my PC is shut off.

In real time mode the program tells the Mixer to reassign the "Line-In" from "Speakers" to "Wave-In" and assigns the output from the program "Wave-Out" to "Speakers" instead. On exit the program restores the assignments. If you abort the program, it could leave "Line-In" or "Wave-Out" disconnected from the "Speakers".

If this happens simply restart the program and shut it down normally.

By the way:
You can set your Mixer settings anytime by running the MS-Windows "Volume Control" program.

From the "Start" menu look for either of these:
Start/Programs/Accessories/Multimedia/Volume Control
Start/Programs/Accessories/Entertainment/Volume Control

Generally everything should have it's "Mute" box cleared (blank) and the volume settings up at least a little from their bottoms. Note that the "Master Volume" "Mute all" box and volume settings override everything else.

Thank you for your interest in my program!

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(c) 1999-2009, Thomas F. Swezey. All rights reserved.