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Re: [Amps] PSK-31

To: "" <>
Subject: Re: [Amps] PSK-31
From: "Jim Brown" <>
Date: Mon, 05 Jun 2006 09:10:51 -0700
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On Mon, 5 Jun 2006 11:37:20 -0400, Harold  Mandel wrote:

>I want to get active on PSK-31, and cannot find info on
>receiving intelligence (versus garbage characters).

I strongly recommend the FREEware called PSK31, which is part of 
the FREEware Ham Radio Deluxe suite of programs for radio control, 
logging, and mapping. Works really well, absolutely painless to 
use. It's written by Simon Brown, HB9DRV. Find it here:

The computer, using its audio card as I/O decodes received PSK31 
and encodes your signal for transmission. In one screen window, it 
is able to simultaneously decode and display a dozen or more 
different signals! You then choose one of them to talk to, and the 
encode/decode function switches to that frequency. 

One VERY important caveat. Any distortion in the audio chain, as 
well as the RF chain, will show up as another copy of your signal, 
shifted in frequency from the main one. There are four common 
places where this distortion can occur.

1) The output of your sound card. The distortion in most sound 
cards, even "good" ones, begins to rise several dB below clip. 
I've done some testing, and found that the distortion in mine (an 
IBM laptop) drops from roughly -30 to -42 re: signal just by 
dropping the output level by 6 dB. I look at distortion on an 
audio spectrum an analyzer. You can do this before connecting the 
computer to your radio. 

2) The input of yor radio. For best signal to noise, your sound 
card should run near the top of its dynamic range (see #1). This 
means that you are likely to need a simple resistive pad (voltage 
divider) at the input of your radio (even when it is called a line 
level input). 

3) Your transceiver's RF stages. PSK31 is a VERY efficient means 
of transmission (at least comparable to CW), and a little bit of 
power goes a long way. Again, running a few dB down will reduce 
the distortion product (and for dissipation reasons, most rigs 
want to be derated 3 dB for keydown modes like PSK31 anyway). 

4) The same rules that apply to keeping distortion low on your amp 
apply equally to PSK31. And remember, a little bit of power goes a 
long way. 

Jim Brown K9YC

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