Message-ID: <002901c1e03a$01a06b60$516152d5@it>
From: "Giulio Scaroni" <scaroni@phoenix.it>
To: rsgb_lf_group@blacksheep.org
References: <000c01c201b5$c3b19a20$39e9fc3e@l8p8y6>
Subject: LF: Re: bandwidth
Date: Wed, 10 Apr 2002 04:47:06 +0200
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<DIV><FONT size=2>Hi Mal,</FONT></DIV>
<DIV><FONT size=2>i not agree with your comment, here i have made many test with 
narrow band in QRSS, but using or not using an external DSP is exatly the same, 
i have aTimewave 599zx, but for qrs no difference.</FONT></DIV>
<DIV><FONT size=2>Also, with narrow bandwidht in IF stage from 2.3 Khz to 250 is 
the same when you using the PC and sound card, the only thing is that if we have 
an interference in IF bandwidht is better yes the narrow IF filters.(here in 
Italy with only 4 active LF station we do not have this problem, hi hi 
hi)</FONT></DIV>
<DIV><FONT size=2>Another thing to remember is that with crash like the 
tundestorm, the narrow filter make the impulse much more longer than with wide 
filter, with DSP filter this situation is not present...., so with crash better 
is wide filter and then dsp filter made by FFT PC program.</FONT></DIV>
<DIV><FONT size=2>Another situation in aural CW, the narrower bandwidht the 
better is the reception, also in IF and AF with DSP.</FONT></DIV>
<DIV><FONT size=2>Last qso that i have had with M0BMU, was in aural cw but 
signal was audible only with 20 Hz DSP filtering and narrow filter in IF 
stage!!!</FONT></DIV>
<DIV><FONT size=2>73 to all de IK2DED Giulio</FONT></DIV>
<DIV>&nbsp;</DIV>
<BLOCKQUOTE 
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  <DIV>&nbsp;</DIV>
  <DIV><FONT face=Arial size=2>Some recent comments seem to indicate that all 
  selectivity should be left to the FFT when using computer derived programs 
  like ARGO and associated type programmes for narrow frequency modes like QRS. 
  </FONT></DIV>
  <DIV><FONT face=Arial size=2>My approach is to feed the RX audio to the 
  computer sound card at the narrowest bandwidth possible, in the case of the 
  pegelmessers at 20 hz b/w. When using conventional receivers with b/widths 
  around 200 hz I then use an external audio DSP unit and again reduce the 
  bandwidth to the narrowest possible. Weak signals stand out a lot better when 
  using this method. On normal cw signals using the most narrow bandwidth 
  possible, commensurate with speed, makes a big difference to hearing the 
  signal. Signals that are barely audible with a 300 - 1000 hz filter are 
  perfectly readable with a 20 - 50 hz filter, the signal over noise is improved 
  dramatically.</FONT></DIV>
  <DIV><FONT face=Arial size=2>The same applies to all modes of signal, minimum 
  bandwidth to achieve the object.</FONT></DIV>
  <DIV><FONT face=Arial size=2>This is normal commercial practice but some radio 
  amateurs are still working in the dark.</FONT></DIV>
  <DIV><FONT face=Arial size=2>G3KEV</FONT></DIV>
  <DIV>&nbsp;</DIV>
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